diff --git a/src/SIPSorcery.VP8/DebugProbe.cs b/src/SIPSorcery.VP8/DebugProbe.cs
index a70282a9e..9a3afdfc4 100644
--- a/src/SIPSorcery.VP8/DebugProbe.cs
+++ b/src/SIPSorcery.VP8/DebugProbe.cs
@@ -19,6 +19,7 @@
 //-----------------------------------------------------------------------------
 
 using System.Diagnostics;
+using System.Text;
 
 namespace Vpx.Net
 {
@@ -30,13 +31,14 @@ public static void DumpMotionVectors(MODE_INFO[] mip, int macroBlockCols, int ma
 			Debug.WriteLine("Macro Block Modes:");
 			for (int i = 0; i < macroBlockRows + 1; i++)
 			{
-				string rowStr = $"Row {i} | ";
+                var rowBuilder = new StringBuilder().Append("Row ").Append(i).Append(" | ");
 				for (int j = 0; j < macroBlockCols + 1; j++)
 				{
 					byte yMode = mip[i * (macroBlockRows + 1) + j].mbmi.mode;
 					byte uvMode = mip[i * (macroBlockRows + 1) + j].mbmi.uv_mode;
-					rowStr += $"y={yMode}, uvMode={uvMode} | ";
+                    rowBuilder.Append("y=").Append(yMode).Append(", uvMode=").Append(uvMode).Append(" | ");
 				}
+                string rowStr = rowBuilder.ToString();
 				Debug.WriteLine(rowStr);
 			}
 
@@ -54,15 +56,20 @@ public static void DumpMotionVectors(MODE_INFO[] mip, int macroBlockCols, int ma
 		public static string GetBModeInfoMatrix(b_mode_info[] bModes)
         {
 			// The array will always be 16 elements.
-			string matrixStr = null;
+            var matrixBuilder = new StringBuilder();
 
 			for(int row=0; row<4; row++)
             {
-				matrixStr += $"[{bModes[row * 4].mv.as_int},{bModes[row * 4 + 1].mv.as_int}" +
-							 $",{bModes[row * 4  +2].mv.as_int},{bModes[row * 4 + 3].mv.as_int}]\n"; 
+                matrixBuilder
+                    .Append('[')
+                    .Append(bModes[row * 4].mv.as_int).Append(',')
+                    .Append(bModes[row * 4 + 1].mv.as_int).Append(',')
+                    .Append(bModes[row * 4 + 2].mv.as_int).Append(',')
+                    .Append(bModes[row * 4 + 3].mv.as_int)
+                    .Append("]\n");
 			}
 
-			return matrixStr;
+            return matrixBuilder.ToString();
         }
 
 		public static unsafe void DumpMacroBlock(MACROBLOCKD macroBlock, int macroBlockIndex)
@@ -89,11 +96,12 @@ public static unsafe void DumpSubBlockCoefficients(MACROBLOCKD macroBlock)
             for(int i=0; i< macroBlock.block.Length; i++)
             {
                 var subBlock = macroBlock.block[i];
-                string qCoeff = null;
+                var qCoeffBuilder = new StringBuilder();
                 for(int j=subBlock.qcoeff.Index; j< subBlock.qcoeff.Index+16; j++)
                 {
-                    qCoeff += subBlock.qcoeff.src()[j].ToString() + ",";
+                    qCoeffBuilder.Append(subBlock.qcoeff.src()[j]).Append(',');
                 }
+                string qCoeff = qCoeffBuilder.ToString();
                 Debug.WriteLine($"block[{i}].qcoeff={qCoeff}");
             }
 
@@ -104,11 +112,12 @@ public static unsafe void DumpSubBlockCoefficients(MACROBLOCKD macroBlock)
             for (int i = 0; i < macroBlock.block.Length; i++)
             {
                 var subBlock = macroBlock.block[i];
-                string dqCoeff = null;
+                var dqCoeffBuilder = new StringBuilder();
                 for (int j = subBlock.dqcoeff.Index; j < subBlock.dqcoeff.Index + 16; j++)
                 {
-                    dqCoeff += subBlock.dqcoeff.src()[j].ToString() + ",";
+                    dqCoeffBuilder.Append(subBlock.dqcoeff.src()[j]).Append(',');
                 }
+                string dqCoeff = dqCoeffBuilder.ToString();
                 Debug.WriteLine($"block[{i}].dqcoeff={dqCoeff}");
             }
 
@@ -160,21 +169,21 @@ public static class DebugProbeHexStr
 
         public unsafe static string ToHexStr(byte* buffer, int length, char? separator = null)
         {
-            string rv = string.Empty;
+            var builder = new StringBuilder(length * (separator == null ? 2 : 3));
 
             for (int i = 0; i < length; i++)
             {
                 var val = buffer[i];
-                rv += hexmap[val >> 4];
-                rv += hexmap[val & 15];
+                builder.Append(hexmap[val >> 4]);
+                builder.Append(hexmap[val & 15]);
 
                 if (separator != null && i != length - 1)
                 {
-                    rv += separator;
+                    builder.Append(separator);
                 }
             }
 
-            return rv.ToLower();
+            return builder.ToString().ToLower();
         }
     }
 }
diff --git a/src/SIPSorcery.VP8/VP8Codec.cs b/src/SIPSorcery.VP8/VP8Codec.cs
index 07d348aee..db0e5c41a 100644
--- a/src/SIPSorcery.VP8/VP8Codec.cs
+++ b/src/SIPSorcery.VP8/VP8Codec.cs
@@ -155,7 +155,7 @@ public byte[] EncodeVideo(int width, int height, byte[] sample, VideoPixelFormat
                     // The foundation encoder requires multiples of 16 — no
                     // padding/cropping support yet.
                     throw new NotSupportedException(
-                        "Width and height must be positive multiples of 16. Got " + width + "x" + height + ".");
+                        $"Width and height must be positive multiples of 16. Got {width}x{height}.");
                 }
 
                 // Convert the input sample into planar I420.
@@ -168,8 +168,7 @@ public byte[] EncodeVideo(int width, int height, byte[] sample, VideoPixelFormat
                 if (i420.Length != ySize + 2 * cSize)
                 {
                     throw new ArgumentException(
-                        "I420 buffer length " + i420.Length + " does not match expected " +
-                        (ySize + 2 * cSize) + " for " + width + "x" + height + ".");
+                        $"I420 buffer length {i420.Length} does not match expected {ySize + 2 * cSize} for {width}x{height}.");
                 }
 
                 if (_srcY == null || _srcY.Length < ySize) { _srcY = new byte[ySize]; }
@@ -228,7 +227,7 @@ public unsafe IEnumerable<VideoSample> DecodeVideo(byte[] frame, VideoPixelForma
                     //logger.LogDebug($"VP8 decode result {result}.");
                     if (result != vpx_codec_err_t.VPX_CODEC_OK)
                     {
-                        logger.LogWarning($"VP8 decode of video sample failed with {result}.");
+                        logger.LogWarning("VP8 decode of video sample failed with {Result}.", result);
                     }
                 }
 
diff --git a/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsClient.cs b/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsClient.cs
index 2eaae0613..eecf15672 100644
--- a/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsClient.cs
+++ b/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsClient.cs
@@ -171,13 +171,14 @@ public override void NotifyAlertRaised(short alertLevel, short alertDescription,
         {
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS client raised alert: " + AlertLevel.GetText(alertLevel) + ", " + AlertDescription.GetText(alertDescription));
+                Log.Debug("DTLS client raised alert: {AlertLevel}, {AlertDescription}.",
+                    AlertLevel.GetText(alertLevel), AlertDescription.GetText(alertDescription));
             }
             if (message != null)
             {
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("> " + message);
+                    Log.Debug("> {Message}", message);
                 }
             }
             if (cause != null)
@@ -193,7 +194,8 @@ public override void NotifyAlertReceived(short level, short alertDescription)
         {
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS client received alert: " + AlertLevel.GetText(level) + ", " + AlertDescription.GetText(alertDescription));
+                Log.Debug("DTLS client received alert: {AlertLevel}, {AlertDescription}.",
+                    AlertLevel.GetText(level), AlertDescription.GetText(alertDescription));
             }
 
             TlsAlertTypesEnum alertType = TlsAlertTypesEnum.Unassigned;
@@ -217,7 +219,7 @@ public override void NotifyServerVersion(ProtocolVersion serverVersion)
 
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS client negotiated " + serverVersion);
+                Log.Debug("DTLS client negotiated {ServerVersion}.", serverVersion);
             }
         }
 
@@ -235,7 +237,7 @@ public override void NotifyHandshakeComplete()
             {
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("Client ALPN: " + protocolName.GetUtf8Decoding());
+                    Log.Debug("Client ALPN: {ApplicationProtocol}.", protocolName.GetUtf8Decoding());
                 }
             }
 
@@ -251,14 +253,14 @@ public override void NotifyHandshakeComplete()
                     {
                         if (Log.DebugEnabled)
                         {
-                            Log.Debug("Client resumed session: " + hex);
+                            Log.Debug("Client resumed session: {SessionIdHex}.", hex);
                         }
                     }
                     else
                     {
                         if (Log.DebugEnabled)
                         {
-                            Log.Debug("Client established session: " + hex);
+                            Log.Debug("Client established session: {SessionIdHex}.", hex);
                         }
                     }
 
@@ -270,14 +272,14 @@ public override void NotifyHandshakeComplete()
                 {
                     if (Log.DebugEnabled)
                     {
-                        Log.Debug("Client 'tls-server-end-point': " + ToHexString(tlsServerEndPoint));
+                        Log.Debug("Client 'tls-server-end-point': {TlsServerEndPoint}.", ToHexString(tlsServerEndPoint));
                     }
                 }
 
                 byte[] tlsUnique = m_context.ExportChannelBinding(ChannelBinding.tls_unique);
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("Client 'tls-unique': " + ToHexString(tlsUnique));
+                    Log.Debug("Client 'tls-unique': {TlsUnique}.", ToHexString(tlsUnique));
                 }
             }
 
@@ -326,14 +328,15 @@ public void NotifyServerCertificate(TlsServerCertificate serverCertificate)
 
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("DTLS client received server certificate chain of length " + chain.Length);
+                    Log.Debug("DTLS client received server certificate chain of length {CertificateCount}.", chain.Length);
                 }
                 for (int i = 0; i != chain.Length; i++)
                 {
                     X509CertificateStructure entry = X509CertificateStructure.GetInstance(chain[i].GetEncoded());
                     if (Log.DebugEnabled)
                     {
-                        Log.Debug("DTLS client fingerprint:SHA-256 " + DtlsCertificateUtils.Fingerprint(entry) + " (" + entry.Subject + ")");
+                        Log.Debug("DTLS client fingerprint:SHA-256 {Fingerprint} ({Subject}).",
+                            DtlsCertificateUtils.Fingerprint(entry), entry.Subject);
                     }
                 }
 
diff --git a/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsServer.cs b/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsServer.cs
index 6b1b91262..cc1e20ee9 100644
--- a/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsServer.cs
+++ b/src/SIPSorcery/net/DtlsSrtp/Lib/DTLS/DtlsServer.cs
@@ -164,14 +164,15 @@ public override void NotifyAlertRaised(short alertLevel, short alertDescription,
         {
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS server raised alert: " + AlertLevel.GetText(alertLevel) + ", " + AlertDescription.GetText(alertDescription));
+                Log.Debug("DTLS server raised alert: {AlertLevel}, {AlertDescription}.",
+                    AlertLevel.GetText(alertLevel), AlertDescription.GetText(alertDescription));
             }
 
             if (message != null)
             {
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("> " + message);
+                    Log.Debug("> {Message}", message);
                 }
             }
             if (cause != null)
@@ -187,7 +188,8 @@ public override void NotifyAlertReceived(short level, short alertDescription)
         {
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS server received alert: " + AlertLevel.GetText(level) + ", " + AlertDescription.GetText(alertDescription));
+                Log.Debug("DTLS server received alert: {AlertLevel}, {AlertDescription}.",
+                    AlertLevel.GetText(level), AlertDescription.GetText(alertDescription));
             }
 
             TlsAlertTypesEnum alertType = TlsAlertTypesEnum.Unassigned;
@@ -210,7 +212,7 @@ public override ProtocolVersion GetServerVersion()
             ProtocolVersion serverVersion = base.GetServerVersion();
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS server negotiated " + serverVersion);
+                Log.Debug("DTLS server negotiated {ServerVersion}.", serverVersion);
             }
             return serverVersion;
         }
@@ -239,7 +241,7 @@ public override void NotifyClientCertificate(Certificate clientCertificate)
 
             if (Log.DebugEnabled)
             {
-                Log.Debug("DTLS server received client certificate chain of length " + chain.Length);
+                Log.Debug("DTLS server received client certificate chain of length {CertificateCount}.", chain.Length);
             }
 
             for (int i = 0; i != chain.Length; i++)
@@ -247,7 +249,8 @@ public override void NotifyClientCertificate(Certificate clientCertificate)
                 X509CertificateStructure entry = X509CertificateStructure.GetInstance(chain[i].GetEncoded());
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("    fingerprint:SHA-256 " + DtlsCertificateUtils.Fingerprint(entry) + " (" + entry.Subject + ")");
+                    Log.Debug("fingerprint:SHA-256 {Fingerprint} ({Subject}).",
+                        DtlsCertificateUtils.Fingerprint(entry), entry.Subject);
                 }
             }
         }
@@ -261,20 +264,20 @@ public override void NotifyHandshakeComplete()
             {
                 if (Log.DebugEnabled)
                 {
-                    Log.Debug("Server ALPN: " + protocolName.GetUtf8Decoding());
+                    Log.Debug("Server ALPN: {ApplicationProtocol}.", protocolName.GetUtf8Decoding());
                 }
             }
 
             byte[] tlsServerEndPoint = m_context.ExportChannelBinding(ChannelBinding.tls_server_end_point);
             if (Log.DebugEnabled)
             {
-                Log.Debug("Server 'tls-server-end-point': " + ToHexString(tlsServerEndPoint));
+                Log.Debug("Server 'tls-server-end-point': {TlsServerEndPoint}.", ToHexString(tlsServerEndPoint));
             }
 
             byte[] tlsUnique = m_context.ExportChannelBinding(ChannelBinding.tls_unique);
             if (Log.DebugEnabled)
             {
-                Log.Debug("Server 'tls-unique': " + ToHexString(tlsUnique));
+                Log.Debug("Server 'tls-unique': {TlsUnique}.", ToHexString(tlsUnique));
             }
 
             OnHandshakeCompleted?.Invoke(this, new DtlsHandshakeCompletedEventArgs(m_context.SecurityParameters));
diff --git a/src/SIPSorcery/net/DtlsSrtp/Lib/Log.cs b/src/SIPSorcery/net/DtlsSrtp/Lib/Log.cs
index 765fa095f..fb4e5bd7d 100644
--- a/src/SIPSorcery/net/DtlsSrtp/Lib/Log.cs
+++ b/src/SIPSorcery/net/DtlsSrtp/Lib/Log.cs
@@ -20,6 +20,8 @@
 // SOFTWARE.
 
 using System;
+using System.Globalization;
+using System.Text.RegularExpressions;
 
 namespace SIPSorcery.Net.SharpSRTP
 {
@@ -53,6 +55,11 @@ public static void Debug(string message, Exception ex = null)
             SinkDebug(message, ex);
         }
 
+        public static void Debug(string messageTemplate, params object[] args)
+        {
+            SinkDebug(FormatTemplate(messageTemplate, args), null);
+        }
+
         public static bool InfoEnabled { get; set; }
 #if DEBUG
             = true;
@@ -67,5 +74,19 @@ public static void Info(string message, Exception ex = null)
         public static Action<string, Exception> SinkTrace = new Action<string, Exception>((m, ex) => { System.Diagnostics.Debug.WriteLine(m); });
         public static Action<string, Exception> SinkDebug = new Action<string, Exception>((m, ex) => { System.Diagnostics.Debug.WriteLine(m); });
         public static Action<string, Exception> SinkInfo = new Action<string, Exception>((m, ex) => { System.Diagnostics.Debug.WriteLine(m); });
+
+        private static readonly Regex MessageTemplateRegex = new Regex(@"(?<!\{)\{[^{}]+\}(?!\})", RegexOptions.Compiled);
+
+        private static string FormatTemplate(string messageTemplate, object[] args)
+        {
+            if (string.IsNullOrEmpty(messageTemplate) || args == null || args.Length == 0)
+            {
+                return messageTemplate;
+            }
+
+            int index = 0;
+            string compositeFormat = MessageTemplateRegex.Replace(messageTemplate, _ => $"{{{index++}}}");
+            return string.Format(CultureInfo.InvariantCulture, compositeFormat, args);
+        }
     }
 }
diff --git a/src/SIPSorcery/net/ICE/RTCIceCandidate.cs b/src/SIPSorcery/net/ICE/RTCIceCandidate.cs
index 604637dc8..8c869775a 100644
--- a/src/SIPSorcery/net/ICE/RTCIceCandidate.cs
+++ b/src/SIPSorcery/net/ICE/RTCIceCandidate.cs
@@ -248,24 +248,11 @@ public override string ToString()
                 string candidateStr;
                 if (protocol == RTCIceProtocol.tcp)
                 {
-                    candidateStr = String.Format("{0} {1} tcp {2} {3} {4} typ {5} tcptype {6} generation 0",
-                        foundation,
-                        component.GetHashCode(),
-                        priority,
-                        address,
-                        port,
-                        type,
-                        tcpType);
+                    candidateStr = $"{foundation} {component.GetHashCode()} tcp {priority} {address} {port} typ {type} tcptype {tcpType} generation 0";
                 }
                 else
                 {
-                    candidateStr = String.Format("{0} {1} udp {2} {3} {4} typ {5} generation 0",
-                        foundation,
-                        component.GetHashCode(),
-                        priority,
-                        address,
-                        port,
-                        type);
+                    candidateStr = $"{foundation} {component.GetHashCode()} udp {priority} {address} {port} typ {type} generation 0";
                 }
 
                 return candidateStr;
@@ -282,28 +269,11 @@ public override string ToString()
                 string candidateStr;
                 if (protocol == RTCIceProtocol.tcp)
                 {
-                    candidateStr = String.Format("{0} {1} tcp {2} {3} {4} typ {5} tcptype {6} raddr {7} rport {8} generation 0",
-                        foundation,
-                        component.GetHashCode(),
-                        priority,
-                        address,
-                        port,
-                        type,
-                        tcpType,
-                        relAddr,
-                        relatedPort);
+                    candidateStr = $"{foundation} {component.GetHashCode()} tcp {priority} {address} {port} typ {type} tcptype {tcpType} raddr {relAddr} rport {relatedPort} generation 0";
                 }
                 else
                 {
-                    candidateStr = String.Format("{0} {1} udp {2} {3} {4} typ {5} raddr {6} rport {7} generation 0",
-                        foundation,
-                        component.GetHashCode(),
-                        priority,
-                        address,
-                        port,
-                        type,
-                        relAddr,
-                        relatedPort);
+                    candidateStr = $"{foundation} {component.GetHashCode()} udp {priority} {address} {port} typ {type} raddr {relAddr} rport {relatedPort} generation 0";
                 }
 
                 return candidateStr;
@@ -383,7 +353,7 @@ public string toJSON()
                 sdpMid = sdpMid ?? sdpMLineIndex.ToString(),
                 sdpMLineIndex = sdpMLineIndex,
                 usernameFragment = usernameFragment,
-                candidate = CANDIDATE_PREFIX + ":" + this.ToString()
+                candidate = $"{CANDIDATE_PREFIX}:{this}"
             };
 
             return rtcCandInit.toJSON();
diff --git a/src/SIPSorcery/net/ICE/RtpIceChannel.cs b/src/SIPSorcery/net/ICE/RtpIceChannel.cs
index fdae5ebd3..29bc9d486 100644
--- a/src/SIPSorcery/net/ICE/RtpIceChannel.cs
+++ b/src/SIPSorcery/net/ICE/RtpIceChannel.cs
@@ -1121,7 +1121,7 @@ private void RefreshTurn(Object state)
             }
             catch (Exception excp)
             {
-                logger.LogError(excp, "Exception " + nameof(RefreshTurn) + ". {ErrorMessage}", excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(RefreshTurn));
             }
         }
 
@@ -1308,12 +1308,12 @@ private async Task UpdateChecklist(RTCIceCandidate localCandidate, RTCIceCandida
         {
             if (localCandidate == null)
             {
-                logger.LogError(nameof(UpdateChecklist) + " the local candidate supplied to UpdateChecklist was null.");
+                logger.LogError("{Method} the local candidate supplied to UpdateChecklist was null.", nameof(UpdateChecklist));
                 return;
             }
             else if (remoteCandidate == null)
             {
-                logger.LogError(nameof(UpdateChecklist) + " the remote candidate supplied to UpdateChecklist was null.");
+                logger.LogError("{Method} the remote candidate supplied to UpdateChecklist was null.", nameof(UpdateChecklist));
                 return;
             }
 
@@ -1323,7 +1323,7 @@ private async Task UpdateChecklist(RTCIceCandidate localCandidate, RTCIceCandida
                 // Attempt to resolve the remote candidate address.
                 if (!IPAddress.TryParse(remoteCandidate.address, out var remoteCandidateIPAddr))
                 {
-                    if (remoteCandidate.address.ToLower().EndsWith(MDNS_TLD))
+                    if (remoteCandidate.address.EndsWith(MDNS_TLD, StringComparison.OrdinalIgnoreCase))
                     {
                         var addresses = await ResolveMdnsName(remoteCandidate).ConfigureAwait(false);
                         if (addresses.Length == 0)
@@ -1418,7 +1418,7 @@ private async Task UpdateChecklist(RTCIceCandidate localCandidate, RTCIceCandida
             }
             catch (Exception excp)
             {
-                logger.LogError(excp, "Exception " + nameof(UpdateChecklist) + ". {ErrorMessage}", excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(UpdateChecklist));
             }
         }
 
@@ -1760,7 +1760,7 @@ private void SendSTUNBindingRequest(ChecklistEntry candidatePair, bool setUseCan
         {
             STUNMessage stunRequest = new STUNMessage(STUNMessageTypesEnum.BindingRequest);
             stunRequest.Header.TransactionId = Encoding.ASCII.GetBytes(candidatePair.RequestTransactionID);
-            stunRequest.AddUsernameAttribute(RemoteIceUser + ":" + LocalIceUser);
+            stunRequest.AddUsernameAttribute($"{RemoteIceUser}:{LocalIceUser}");
             stunRequest.Attributes.Add(new STUNAttribute(STUNAttributeTypesEnum.Priority, BitConverter.GetBytes(candidatePair.LocalPriority)));
 
             if (IsController)
@@ -2725,7 +2725,8 @@ private async Task<IPAddress[]> ResolveMdnsName(RTCIceCandidate candidate)
             {
                 if (MdnsResolve != null)
                 {
-                    logger.LogWarning("RTP ICE channel has both "+ nameof(MdnsGetAddresses) + " and " + nameof(MdnsGetAddresses) + " set. Only " + nameof(MdnsGetAddresses) + " will be used.");
+                    logger.LogWarning("RTP ICE channel has both {PrimaryResolver} and {SecondaryResolver} set. Only {SelectedResolver} will be used.",
+                        nameof(MdnsGetAddresses), nameof(MdnsResolve), nameof(MdnsGetAddresses));
                 }
                 return await MdnsGetAddresses(candidate.address).ConfigureAwait(false);
             }
diff --git a/src/SIPSorcery/net/RTCP/RTCPFeedback.cs b/src/SIPSorcery/net/RTCP/RTCPFeedback.cs
index ba598d29f..8f6542705 100644
--- a/src/SIPSorcery/net/RTCP/RTCPFeedback.cs
+++ b/src/SIPSorcery/net/RTCP/RTCPFeedback.cs
@@ -172,23 +172,23 @@ public RTCPFeedback(byte[] packet)
 
             switch (Header)
             {
-                case var x when x.PacketType == RTCPReportTypesEnum.RTPFB && x.FeedbackMessageType == RTCPFeedbackTypesEnum.RTCP_SR_REQ:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.RTPFB && Header.FeedbackMessageType == RTCPFeedbackTypesEnum.RTCP_SR_REQ:
                     SENDER_PAYLOAD_SIZE = 8;
                     // PLI feedback reports do no have any additional parameters.
                     break;
-                case var x when x.PacketType == RTCPReportTypesEnum.RTPFB:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.RTPFB:
                     SENDER_PAYLOAD_SIZE = 12;
                     PID = BinaryPrimitives.ReadUInt16BigEndian(packet.AsSpan(payloadIndex + 8));
                     BLP = BinaryPrimitives.ReadUInt16BigEndian(packet.AsSpan(payloadIndex + 10));
                     break;
 
-                case var x when x.PacketType == RTCPReportTypesEnum.PSFB && x.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.PLI:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.PSFB && Header.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.PLI:
                     SENDER_PAYLOAD_SIZE = 8;
                     break;
 
                 // We have a lot of different kind of extension messages
                 // In case below we will handle the specific REMB Message https://datatracker.ietf.org/doc/html/draft-alvestrand-rmcat-remb-03#page-3
-                case var x when x.PacketType == RTCPReportTypesEnum.PSFB && x.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.AFB:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.PSFB && Header.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.AFB:
 
                     // 0                   1                   2                   3
                     // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@@ -267,17 +267,17 @@ public byte[] GetBytes()
 
             switch (Header)
             {
-                case var x when x.PacketType == RTCPReportTypesEnum.RTPFB && x.FeedbackMessageType == RTCPFeedbackTypesEnum.RTCP_SR_REQ:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.RTPFB && Header.FeedbackMessageType == RTCPFeedbackTypesEnum.RTCP_SR_REQ:
                     // PLI feedback reports do no have any additional parameters.
                     break;
-                case var x when x.PacketType == RTCPReportTypesEnum.RTPFB:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.RTPFB:
                     BinaryPrimitives.WriteUInt16BigEndian(buffer.AsSpan(payloadIndex + 8), PID);
                     BinaryPrimitives.WriteUInt16BigEndian(buffer.AsSpan(payloadIndex + 10), BLP);
                     break;
 
-                case var x when x.PacketType == RTCPReportTypesEnum.PSFB && x.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.PLI:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.PSFB && Header.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.PLI:
                     break;
-                case var x when x.PacketType == RTCPReportTypesEnum.PSFB && x.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.AFB:
+                case var _ when Header.PacketType == RTCPReportTypesEnum.PSFB && Header.PayloadFeedbackMessageType == PSFBFeedbackTypesEnum.AFB:
 
                     // There's have a lot of different kind of extension messages
                     // In case below we will handle the specific REMB Message https://datatracker.ietf.org/doc/html/draft-alvestrand-rmcat-remb-03#page-3
diff --git a/src/SIPSorcery/net/RTCP/RTCPHeader.cs b/src/SIPSorcery/net/RTCP/RTCPHeader.cs
index ec59cfa53..9ea82cbef 100644
--- a/src/SIPSorcery/net/RTCP/RTCPHeader.cs
+++ b/src/SIPSorcery/net/RTCP/RTCPHeader.cs
@@ -177,7 +177,7 @@ public byte[] GetHeader(int receptionReportCount, UInt16 length)
         {
             if (receptionReportCount > MAX_RECEPTIONREPORT_COUNT)
             {
-                throw new ApplicationException("The Reception Report Count value cannot be larger than " + MAX_RECEPTIONREPORT_COUNT + ".");
+                throw new ApplicationException($"The Reception Report Count value cannot be larger than {MAX_RECEPTIONREPORT_COUNT}.");
             }
 
             ReceptionReportCount = receptionReportCount;
diff --git a/src/SIPSorcery/net/RTCP/RTCPTWCCFeedback.cs b/src/SIPSorcery/net/RTCP/RTCPTWCCFeedback.cs
index 319f8e144..26be2150b 100644
--- a/src/SIPSorcery/net/RTCP/RTCPTWCCFeedback.cs
+++ b/src/SIPSorcery/net/RTCP/RTCPTWCCFeedback.cs
@@ -524,9 +524,7 @@ public override string ToString()
             var packetStatusInfo = string.Join(", ", PacketStatuses.Select(ps =>
                 $"Seq:{ps.SequenceNumber}({ps.Status}{(ps.Delta.HasValue ? $",Δ:{ps.Delta.Value}" : "")})"));
 
-            return $"TWCC Feedback: SenderSSRC={SenderSSRC}, MediaSSRC={MediaSSRC}, BaseSeq={BaseSequenceNumber}, " +
-                   $"StatusCount={PacketStatusCount}, RefTime={ReferenceTime} (1/64 sec), " +
-                   $"FbkPktCount={FeedbackPacketCount}, PacketStatuses=[{packetStatusInfo}]";
+            return $"TWCC Feedback: SenderSSRC={SenderSSRC}, MediaSSRC={MediaSSRC}, BaseSeq={BaseSequenceNumber}, StatusCount={PacketStatusCount}, RefTime={ReferenceTime} (1/64 sec), FbkPktCount={FeedbackPacketCount}, PacketStatuses=[{packetStatusInfo}]";
         }
 
         #region Helper Methods
diff --git a/src/SIPSorcery/net/RTP/RTPHeaderExtensions/TransportWideCCExtension.cs b/src/SIPSorcery/net/RTP/RTPHeaderExtensions/TransportWideCCExtension.cs
index cd6138f00..91a333340 100644
--- a/src/SIPSorcery/net/RTP/RTPHeaderExtensions/TransportWideCCExtension.cs
+++ b/src/SIPSorcery/net/RTP/RTPHeaderExtensions/TransportWideCCExtension.cs
@@ -37,14 +37,9 @@ public class TransportWideCCExtension : RTPHeaderExtension
 
         public override bool MatchesExtension(string uri)
         {
-            switch (uri.ToLower())
-            {
-                case RTP_HEADER_EXTENSION_URI:
-                case "urn:ietf:params:rtp-hdrext:transport-wide-cc": //official urn registered with IANA
-                case "http://www.webrtc.org/experiments/rtp-hdrext/transport-wide-cc-02":
-                    return true;
-            }
-            return false;
+            return string.Equals(uri, RTP_HEADER_EXTENSION_URI, StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(uri, "urn:ietf:params:rtp-hdrext:transport-wide-cc", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(uri, "http://www.webrtc.org/experiments/rtp-hdrext/transport-wide-cc-02", StringComparison.OrdinalIgnoreCase);
         }
 
 
diff --git a/src/SIPSorcery/net/RTP/RTPSession.cs b/src/SIPSorcery/net/RTP/RTPSession.cs
index 398d1d48c..0eeb8797b 100644
--- a/src/SIPSorcery/net/RTP/RTPSession.cs
+++ b/src/SIPSorcery/net/RTP/RTPSession.cs
@@ -24,6 +24,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
@@ -666,35 +667,36 @@ protected void AddRemoteSDPSsrcAttributes(SDPMediaTypesEnum mediaType, List<SDPS
 
         protected void LogRemoteSDPSsrcAttributes()
         {
-            string str = "Audio:[ ";
+            var stringBuilder = new StringBuilder("Audio:[ ");
             foreach (var audioRemoteSDPSsrcAttribute in audioRemoteSDPSsrcAttributes)
             {
                 foreach (var attr in audioRemoteSDPSsrcAttribute)
                 {
-                    str += attr.SSRC + " - ";
+                    stringBuilder.Append(attr.SSRC).Append(" - ");
                 }
             }
-            str += "] \r\n Video: [ ";
+            stringBuilder.Append("] \r\n Video: [ ");
             foreach (var videoRemoteSDPSsrcAttribute in videoRemoteSDPSsrcAttributes)
             {
-                str += " [";
+                stringBuilder.Append(" [");
                 foreach (var attr in videoRemoteSDPSsrcAttribute)
                 {
-                    str += attr.SSRC + " - ";
+                    stringBuilder.Append(attr.SSRC).Append(" - ");
                 }
-                str += "] ";
+                stringBuilder.Append("] ");
             }
-            str += "] \r\n Text: [ ";
+            stringBuilder.Append("] \r\n Text: [ ");
             foreach (var textRemoteSDPSsrcAttribute in textRemoteSDPSsrcAttributes)
             {
-                str += " [";
+                stringBuilder.Append(" [");
                 foreach (var attr in textRemoteSDPSsrcAttribute)
                 {
-                    str += attr.SSRC + " - ";
+                    stringBuilder.Append(attr.SSRC).Append(" - ");
                 }
-                str += "] ";
+                stringBuilder.Append("] ");
             }
-            str += " ]";
+            stringBuilder.Append(" ]");
+            var str = stringBuilder.ToString();
             logger.LogDebug("LogRemoteSDPSsrcAttributes: {RemoteSDPSsrcAttributes}", str);
         }
 
@@ -1231,16 +1233,16 @@ public virtual SetDescriptionResultEnum SetRemoteDescription(SdpType sdpType, SD
                             // Adjust the local track's RTP event capability if the remote party has specified a different payload ID.
                             var currentLocalTrackCapabilities = currentMediaStream.LocalTrack.Capabilities;
                             SDPAudioVideoMediaFormat? localRTPEventCapabilities = null;
-                            if (currentLocalTrackCapabilities.Any(x => x.Name().ToLower() == SDP.TELEPHONE_EVENT_ATTRIBUTE))
+                            if (currentLocalTrackCapabilities.Any(x => string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase)))
                             {
-                                localRTPEventCapabilities = currentLocalTrackCapabilities.First(x => x.Name().ToLower() == SDP.TELEPHONE_EVENT_ATTRIBUTE);
+                                localRTPEventCapabilities = currentLocalTrackCapabilities.First(x => string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase));
                             }
                             else
                             {
                                 localRTPEventCapabilities = MediaStream.DefaultRTPEventFormat;
                             }
 
-                            currentMediaStream.LocalTrack.Capabilities = capabilities.Where(x => x.Name().ToLower() != SDP.TELEPHONE_EVENT_ATTRIBUTE).ToList();
+                            currentMediaStream.LocalTrack.Capabilities = capabilities.Where(x => !string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase)).ToList();
                             if (localRTPEventCapabilities != null)
                             {
                                 currentMediaStream.LocalTrack.Capabilities.Add(localRTPEventCapabilities.Value);
@@ -1251,7 +1253,7 @@ public virtual SetDescriptionResultEnum SetRemoteDescription(SdpType sdpType, SD
                             if (!commonEventFormat.IsEmpty())
                             {
                                 currentMediaStream.NegotiatedRtpEventPayloadID = commonEventFormat.ID;
-                                currentMediaStream.LocalTrack.Capabilities.RemoveAll(x => x.Name().ToLower() == SDP.TELEPHONE_EVENT_ATTRIBUTE);
+                                currentMediaStream.LocalTrack.Capabilities.RemoveAll(x => string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase));
                                 currentMediaStream.LocalTrack.Capabilities.Add(commonEventFormat);
                             }
                         }
@@ -1295,7 +1297,7 @@ public virtual SetDescriptionResultEnum SetRemoteDescription(SdpType sdpType, SD
 
                     if (currentMediaStream.MediaType == SDPMediaTypesEnum.audio)
                     {
-                        if (capabilities?.Where(x => x.Name().ToLower() != SDP.TELEPHONE_EVENT_ATTRIBUTE).Count() == 0)
+                        if (capabilities?.Where(x => !string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase)).Count() == 0)
                         {
                             return SetDescriptionResultEnum.AudioIncompatible;
                         }
diff --git a/src/SIPSorcery/net/RTP/Streams/AudioStream.cs b/src/SIPSorcery/net/RTP/Streams/AudioStream.cs
index 7aa4702b9..7b40b6561 100644
--- a/src/SIPSorcery/net/RTP/Streams/AudioStream.cs
+++ b/src/SIPSorcery/net/RTP/Streams/AudioStream.cs
@@ -201,7 +201,7 @@ public async Task SendDtmfEvent(RTPEvent rtpEvent, CancellationToken cancellatio
             {
                 if (rtpEventInProgress)
                 {
-                    logger.LogWarning(nameof(SendDtmfEvent) + " an RTPEvent is already in progress.");
+                    logger.LogWarning("{Method} an RTPEvent is already in progress.", nameof(SendDtmfEvent));
                     return;
                 }
 
@@ -285,12 +285,12 @@ public virtual Task SendDtmf(byte key, CancellationToken ct)
         public void CheckAudioFormatsNegotiation()
         {
             if (LocalTrack != null &&
-                        LocalTrack.Capabilities.Where(x => x.Name().ToLower() != SDP.TELEPHONE_EVENT_ATTRIBUTE).Count() > 0)
+                        LocalTrack.Capabilities.Where(x => !string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase)).Count() > 0)
             {
                 OnAudioFormatsNegotiatedByIndex?.Invoke(
                             Index,
                             LocalTrack.Capabilities
-                            .Where(x => x.Name().ToLower() != SDP.TELEPHONE_EVENT_ATTRIBUTE)
+                            .Where(x => !string.Equals(x.Name(), SDP.TELEPHONE_EVENT_ATTRIBUTE, StringComparison.OrdinalIgnoreCase))
                             .Select(x => x.ToAudioFormat()).ToList());
             }
         }
diff --git a/src/SIPSorcery/net/RTSP/RTSPClient.cs b/src/SIPSorcery/net/RTSP/RTSPClient.cs
index b6adf8a70..e7db300ee 100644
--- a/src/SIPSorcery/net/RTSP/RTSPClient.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPClient.cs
@@ -89,7 +89,7 @@ public string GetStreamDescription(string url)
                 string hostname = Regex.Match(url, @"rtsp://(?<hostname>\S+?)/").Result("${hostname}");
                 //IPEndPoint rtspEndPoint = DNSResolver.R(hostname, DNS_RESOLUTION_TIMEOUT);
 
-                logger.LogDebug("RTSP Client Connecting to " + hostname + ".");
+                logger.LogDebug("RTSP Client connecting to {Hostname}.", hostname);
                 TcpClient rtspSocket = new TcpClient(hostname, RTSP_PORT);
                 NetworkStream rtspStream = rtspSocket.GetStream();
 
@@ -118,14 +118,14 @@ public string GetStreamDescription(string url)
                     if (rtspMessage.RTSPMessageType == RTSPMessageTypesEnum.Response)
                     {
                         rtspResponse = RTSPResponse.ParseRTSPResponse(rtspMessage);
-                        logger.LogDebug("RTSP Response received: " + rtspResponse.StatusCode + " " + rtspResponse.Status + " " + rtspResponse.ReasonPhrase + ".");
+                        logger.LogDebug("RTSP Response received: {StatusCode} {Status} {ReasonPhrase}.", rtspResponse.StatusCode, rtspResponse.Status, rtspResponse.ReasonPhrase);
                     }
 
                     rtspSDP = rtspResponse.Body;
                 }
                 else
                 {
-                    logger.LogWarning("Socket closed prematurely in GetStreamDescription for " + url + ".");
+                    logger.LogWarning("Socket closed prematurely in {Method} for {Url}.", nameof(GetStreamDescription), url);
                 }
 
                 rtspSocket.Close();
@@ -134,7 +134,7 @@ public string GetStreamDescription(string url)
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception GetStreamDescription. " + excp.Message);
+                logger.LogError(excp, "Exception in {Method}.", nameof(GetStreamDescription));
                 throw excp;
             }
         }
@@ -147,7 +147,7 @@ public void Start(string url)
 
             if (!urlMatch.Success)
             {
-                throw new ApplicationException("The URL provided to the RTSP client was not recognised, " + url + ".");
+                throw new ApplicationException($"The URL provided to the RTSP client was not recognised, {url}.");
             }
             else
             {
@@ -160,7 +160,7 @@ public void Start(string url)
                     hostname = SIPSorcery.Sys.IPSocket.ParseHostFromSocket(hostname);
                 }
 
-                logger.LogDebug("RTSP client connecting to " + hostname + ", port " + port + ".");
+                logger.LogDebug("RTSP client connecting to {Hostname}, port {Port}.", hostname, port);
 
                 _rtspConnection = new TcpClient(hostname, port);
                 _rtspStream = _rtspConnection.GetStream();
@@ -172,7 +172,7 @@ public void Start(string url)
 
                 RTSPRequest rtspRequest = new RTSPRequest(RTSPMethodsEnum.SETUP, url);
                 RTSPHeader rtspHeader = new RTSPHeader(_cseq++, null);
-                rtspHeader.Transport = new RTSPTransportHeader() { ClientRTPPortRange = _rtspSession.RTPPort + "-" + _rtspSession.ControlPort };
+                rtspHeader.Transport = new RTSPTransportHeader() { ClientRTPPortRange = $"{_rtspSession.RTPPort}-{_rtspSession.ControlPort}" };
                 rtspRequest.Header = rtspHeader;
                 string rtspReqStr = rtspRequest.ToString();
 
@@ -202,7 +202,8 @@ public void Start(string url)
                             _rtspSession.RemoteEndPoint = new IPEndPoint((_rtspConnection.Client.RemoteEndPoint as IPEndPoint).Address, setupResponse.Header.Transport.GetServerRTPPort());
                             _rtspSession.Start();
 
-                            logger.LogDebug("RTSP Response received to SETUP: " + setupResponse.Status + ", session ID " + _rtspSession.SessionID + ", server RTP endpoint " + _rtspSession.RemoteEndPoint + ".");
+                            logger.LogDebug("RTSP Response received to SETUP: {Status}, session ID {SessionId}, server RTP endpoint {RemoteEndPoint}.",
+                                setupResponse.Status, _rtspSession.SessionID, _rtspSession.RemoteEndPoint);
 
                             if (OnSetupSuccess != null)
                             {
@@ -211,8 +212,8 @@ public void Start(string url)
                         }
                         else
                         {
-                            logger.LogWarning("RTSP Response received to SETUP: " + setupResponse.Status + ".");
-                            throw new ApplicationException("An error response of " + setupResponse.Status + " was received for an RTSP setup request.");
+                            logger.LogWarning("RTSP Response received to SETUP: {Status}.", setupResponse.Status);
+                            throw new ApplicationException($"An error response of {setupResponse.Status} was received for an RTSP setup request.");
                         }
                     }
                 }
@@ -239,7 +240,7 @@ private void RTPQueueFull()
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception RTSPClient.RTPQueueFull. " + excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(RTPQueueFull));
             }
         }
 
@@ -274,7 +275,7 @@ public void Play()
                 if (rtspMessage.RTSPMessageType == RTSPMessageTypesEnum.Response)
                 {
                     var playResponse = RTSPResponse.ParseRTSPResponse(rtspMessage);
-                    logger.LogDebug("RTSP Response received to PLAY: " + playResponse.StatusCode + " " + playResponse.Status + " " + playResponse.ReasonPhrase + ".");
+                    logger.LogDebug("RTSP Response received to PLAY: {StatusCode} {Status} {ReasonPhrase}.", playResponse.StatusCode, playResponse.Status, playResponse.ReasonPhrase);
                 }
             }
             else
@@ -292,7 +293,7 @@ private void Teardown()
             {
                 if (_rtspStream != null && _rtspConnection.Connected)
                 {
-                    logger.LogDebug("RTSP client sending teardown request for " + _url + ".");
+                    logger.LogDebug("RTSP client sending teardown request for {Url}.", _url);
 
                     RTSPRequest teardownRequest = new RTSPRequest(RTSPMethodsEnum.TEARDOWN, _url);
                     RTSPHeader teardownHeader = new RTSPHeader(_cseq++, _rtspSession.SessionID);
@@ -305,12 +306,12 @@ private void Teardown()
                 }
                 else
                 {
-                    logger.LogDebug("RTSP client did not send teardown request for " + _url + ", the socket was closed.");
+                    logger.LogDebug("RTSP client did not send teardown request for {Url}, the socket was closed.", _url);
                 }
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception RTSPClient.Teardown. " + excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(Teardown));
             }
         }
 
@@ -323,7 +324,7 @@ public void Close()
             {
                 if (!_isClosed)
                 {
-                    logger.LogDebug("RTSP client, closing connection for " + _url + ".");
+                    logger.LogDebug("RTSP client, closing connection for {Url}.", _url);
 
                     _isClosed = true;
                     _sendKeepAlivesMRE.Set();
@@ -343,7 +344,7 @@ public void Close()
                         }
                         catch (Exception rtpStreamExcp)
                         {
-                            logger.LogError("Exception RTSPClient.Close closing RTP stream. " + rtpStreamExcp);
+                            logger.LogError(rtpStreamExcp, "Exception in {Method} closing RTP stream.", nameof(Close));
                         }
                     }
 
@@ -355,7 +356,7 @@ public void Close()
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception RTSPClient.Close. " + excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(Close));
             }
         }
 
@@ -392,7 +393,7 @@ private void ProcessRTPPackets()
                                 }
 
                                 var abbrevURL = (_url.Length <= 50) ? _url : _url.Substring(0, 50);
-                                string rtpTrackingText = String.Format("Url: {0}\r\nRcvd At: {1}\r\nSeq Num: {2}\r\nTS: {3}\r\nPayoad: {4}\r\nFrame Size: {5}\r\nBW: {6}\r\nFrame Rate: {7}", abbrevURL, DateTime.Now.ToString("HH:mm:ss:fff"), rtpPacket.Header.SequenceNumber, rtpPacket.Header.Timestamp, ((SDPMediaFormatsEnum)rtpPacket.Header.PayloadType).ToString(), _lastFrameSize + " bytes", _lastBWCalc.ToString("0.#") + "bps", _lastFrameRate.ToString("0.##") + "fps");
+                                string rtpTrackingText = $"Url: {abbrevURL}\r\nRcvd At: {DateTime.Now:HH:mm:ss:fff}\r\nSeq Num: {rtpPacket.Header.SequenceNumber}\r\nTS: {rtpPacket.Header.Timestamp}\r\nPayoad: {(SDPMediaFormatsEnum)rtpPacket.Header.PayloadType}\r\nFrame Size: {_lastFrameSize} bytes\r\nBW: {_lastBWCalc:0.#}bps\r\nFrame Rate: {_lastFrameRate:0.##}fps";
                                 _rtpTrackingAction(rtpTrackingText);
                             }
 
@@ -440,7 +441,7 @@ private void ProcessRTPPackets()
                                     foreach (var oldFrame in _frames.Where(x => x.Timestamp <= rtpPacket.Header.Timestamp).ToList())
                                     {
                                         System.Diagnostics.Debug.WriteLine("Discarding old frame for timestamp " + oldFrame.Timestamp + ".");
-                                        logger.LogWarning("Discarding old frame for timestamp " + oldFrame.Timestamp + ".");
+                                        logger.LogWarning("Discarding old frame for timestamp {Timestamp}.", oldFrame.Timestamp);
                                         _frames.Remove(oldFrame);
                                     }
 
@@ -461,7 +462,7 @@ private void ProcessRTPPackets()
                                         }
                                         catch (Exception frameReadyExcp)
                                         {
-                                            logger.LogError("Exception RTSPClient.ProcessRTPPackets OnFrameReady. " + frameReadyExcp);
+                                            logger.LogError(frameReadyExcp, "Exception in {Method} OnFrameReady.", nameof(ProcessRTPPackets));
                                         }
                                     }
                                 }
@@ -471,7 +472,8 @@ private void ProcessRTPPackets()
 
                     if (DateTime.Now.Subtract(_lastRTPReceivedAt).TotalSeconds > RTP_TIMEOUT_SECONDS)
                     {
-                        logger.LogWarning("No RTP packets were received on RTSP session " + _rtspSession.SessionID + " for " + RTP_TIMEOUT_SECONDS + ". The session will now be closed.");
+                        logger.LogWarning("No RTP packets were received on RTSP session {SessionId} for {TimeoutSeconds}. The session will now be closed.",
+                            _rtspSession.SessionID, RTP_TIMEOUT_SECONDS);
                         Close();
                     }
                     else
@@ -482,7 +484,7 @@ private void ProcessRTPPackets()
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception RTSPClient.ProcessRTPPackets. " + excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(ProcessRTPPackets));
             }
         }
 
@@ -538,7 +540,7 @@ private void SendKeepAlives()
             }
             catch (Exception excp)
             {
-                logger.LogError("Exception RTSPClient.SendKeepAlives. " + excp);
+                logger.LogError(excp, "Exception in {Method}.", nameof(SendKeepAlives));
             }
         }
     }
diff --git a/src/SIPSorcery/net/RTSP/RTSPHeader.cs b/src/SIPSorcery/net/RTSP/RTSPHeader.cs
index 6c7c2d24d..b29c9031d 100644
--- a/src/SIPSorcery/net/RTSP/RTSPHeader.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPHeader.cs
@@ -17,8 +17,8 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using System.Text.RegularExpressions;
 using Microsoft.Extensions.Logging;
+using Polyfills;
 using SIPSorcery.Sys;
 
 namespace SIPSorcery.Net
@@ -79,37 +79,60 @@ public static RTSPTransportHeader Parse(string header)
             {
                 transportHeader.RawHeader = header;
 
-                string[] fields = header.Split(';');
+                var fields = header.AsSpan();
+                var fieldIndex = 0;
+                Span<Range> fieldKeyValueRange = stackalloc Range[3];
+                foreach (var fieldRange in fields.Split(';'))
+                {
+                    var field = fields[fieldRange];
+                    if (fieldIndex == 0)
+                    {
+                        transportHeader.TransportSpecifier = field.ToString();
+                        fieldIndex++;
+                        continue;
+                    }
 
-                transportHeader.TransportSpecifier = fields[0];
-                transportHeader.BroadcastType = fields[1];
+                    if (fieldIndex == 1)
+                    {
+                        transportHeader.BroadcastType = field.ToString();
+                        fieldIndex++;
+                        continue;
+                    }
 
-                foreach (string field in fields.Where(x => x.Contains('=')))
-                {
-                    string fieldName = field.Split('=')[0];
-                    string fieldValue = field.Split('=')[1];
+                    if (field.Split(fieldKeyValueRange, '=') < 2)
+                    {
+                        continue;
+                    }
 
-                    switch (fieldName.ToLower())
+                    var fieldName = field[fieldKeyValueRange[0]];
+                    var fieldValue = field[fieldKeyValueRange[1]];
+
+                    if (fieldName.Equals(CLIENT_RTP_PORT_FIELD_NAME, StringComparison.OrdinalIgnoreCase))
+                    {
+                        transportHeader.ClientRTPPortRange = fieldValue.Trim().ToString();
+                    }
+                    else if (fieldName.Equals(DESTINATION_FIELD_NAME, StringComparison.OrdinalIgnoreCase))
                     {
-                        case CLIENT_RTP_PORT_FIELD_NAME:
-                            transportHeader.ClientRTPPortRange = fieldValue.Trim();
-                            break;
-                        case DESTINATION_FIELD_NAME:
-                            transportHeader.Destination = fieldValue.Trim();
-                            break;
-                        case SERVER_RTP_PORT_FIELD_NAME:
-                            transportHeader.ServerRTPPortRange = fieldValue.Trim();
-                            break;
-                        case SOURCE_FIELD_NAME:
-                            transportHeader.Source = fieldValue.Trim();
-                            break;
-                        case MODE_FIELD_NAME:
-                            transportHeader.Mode = fieldValue.Trim();
-                            break;
-                        default:
-                            logger.LogWarning("An RTSP Transport header parameter was not recognised: {Field}", field);
-                            break;
+                        transportHeader.Destination = fieldValue.Trim().ToString();
                     }
+                    else if (fieldName.Equals(SERVER_RTP_PORT_FIELD_NAME, StringComparison.OrdinalIgnoreCase))
+                    {
+                        transportHeader.ServerRTPPortRange = fieldValue.Trim().ToString();
+                    }
+                    else if (fieldName.Equals(SOURCE_FIELD_NAME, StringComparison.OrdinalIgnoreCase))
+                    {
+                        transportHeader.Source = fieldValue.Trim().ToString();
+                    }
+                    else if (fieldName.Equals(MODE_FIELD_NAME, StringComparison.OrdinalIgnoreCase))
+                    {
+                        transportHeader.Mode = fieldValue.Trim().ToString();
+                    }
+                    else
+                    {
+                        logger.LogWarning("An RTSP Transport header parameter was not recognised: {Field}", field.ToString());
+                    }
+
+                    fieldIndex++;
                 }
             }
 
@@ -124,11 +147,7 @@ public int GetClientRTPPort()
         {
             if (ClientRTPPortRange.NotNullOrBlank())
             {
-                int clientRTPPort = 0;
-
-                var fields = ClientRTPPortRange.Split('-');
-
-                if (Int32.TryParse(fields[0], out clientRTPPort))
+                if (TryParsePortRange(ClientRTPPortRange.AsSpan(), true, out var clientRTPPort))
                 {
                     return clientRTPPort;
                 }
@@ -145,11 +164,7 @@ public int GetClientRtcpPort()
         {
             if (ClientRTPPortRange.NotNullOrBlank())
             {
-                int clientRTCPPort = 0;
-
-                var fields = ClientRTPPortRange.Split('-');
-
-                if (fields.Length > 1 && Int32.TryParse(fields[1], out clientRTCPPort))
+                if (TryParsePortRange(ClientRTPPortRange.AsSpan(), false, out var clientRTCPPort))
                 {
                     return clientRTCPPort;
                 }
@@ -167,11 +182,7 @@ public int GetServerRTPPort()
         {
             if (ServerRTPPortRange.NotNullOrBlank())
             {
-                int serverRTPPort = 0;
-
-                var fields = ServerRTPPortRange.Split('-');
-
-                if (Int32.TryParse(fields[0], out serverRTPPort))
+                if (TryParsePortRange(ServerRTPPortRange.AsSpan(), true, out var serverRTPPort))
                 {
                     return serverRTPPort;
                 }
@@ -188,11 +199,7 @@ public int GetServerRtcpPort()
         {
             if (ServerRTPPortRange.NotNullOrBlank())
             {
-                int serverRtcpPort = 0;
-
-                var fields = ServerRTPPortRange.Split('-');
-
-                if (fields.Length > 0 && Int32.TryParse(fields[1], out serverRtcpPort))
+                if (TryParsePortRange(ServerRTPPortRange.AsSpan(), false, out var serverRtcpPort))
                 {
                     return serverRtcpPort;
                 }
@@ -201,36 +208,48 @@ public int GetServerRtcpPort()
             return 0;
         }
 
+        private static bool TryParsePortRange(ReadOnlySpan<char> portRange, bool useFirstPort, out int port)
+        {
+            port = 0;
+            portRange = portRange.Trim();
+            Span<Range> portRangeFields = stackalloc Range[3];
+            var portFieldCount = portRange.Split(portRangeFields, '-');
+            var portIndex = useFirstPort ? 0 : 1;
+
+            return portFieldCount > portIndex && int.TryParse(portRange[portRangeFields[portIndex]], out port);
+        }
+
         public override string ToString()
         {
-            string transportHeader = TransportSpecifier + ";" + BroadcastType;
+            var transportHeader = new StringBuilder();
+            transportHeader.Append(TransportSpecifier).Append(';').Append(BroadcastType);
 
             if (Destination.NotNullOrBlank())
             {
-                transportHeader += String.Format(";{0}={1}", DESTINATION_FIELD_NAME, Destination);
+                transportHeader.Append(';').Append(DESTINATION_FIELD_NAME).Append('=').Append(Destination);
             }
 
             if (Source.NotNullOrBlank())
             {
-                transportHeader += String.Format(";{0}={1}", SOURCE_FIELD_NAME, Source);
+                transportHeader.Append(';').Append(SOURCE_FIELD_NAME).Append('=').Append(Source);
             }
 
             if (ClientRTPPortRange.NotNullOrBlank())
             {
-                transportHeader += String.Format(";{0}={1}", CLIENT_RTP_PORT_FIELD_NAME, ClientRTPPortRange);
+                transportHeader.Append(';').Append(CLIENT_RTP_PORT_FIELD_NAME).Append('=').Append(ClientRTPPortRange);
             }
 
             if (ServerRTPPortRange.NotNullOrBlank())
             {
-                transportHeader += String.Format(";{0}={1}", SERVER_RTP_PORT_FIELD_NAME, ServerRTPPortRange);
+                transportHeader.Append(';').Append(SERVER_RTP_PORT_FIELD_NAME).Append('=').Append(ServerRTPPortRange);
             }
 
             if (Mode.NotNullOrBlank())
             {
-                transportHeader += String.Format(";{0}={1}", MODE_FIELD_NAME, Mode);
+                transportHeader.Append(';').Append(MODE_FIELD_NAME).Append('=').Append(Mode);
             }
 
-            return transportHeader;
+            return transportHeader.ToString();
         }
     }
 
@@ -272,13 +291,71 @@ public void AddHeader(string headerName, string value)
 
         public static string[] SplitHeaders(string message)
         {
+            static string NormalizeFoldedHeaderLines(string headerBlock)
+            {
+                var normalised = default(StringBuilder);
+                var segmentStart = 0;
+                var position = 0;
+
+                while (position < headerBlock.Length)
+                {
+                    if (position + 2 < headerBlock.Length &&
+                        headerBlock[position] == '\r' &&
+                        headerBlock[position + 1] == '\n' &&
+                        char.IsWhiteSpace(headerBlock[position + 2]))
+                    {
+                        normalised ??= new StringBuilder(headerBlock.Length);
+                        normalised.Append(headerBlock, segmentStart, position - segmentStart);
+                        normalised.Append(' ');
+
+                        position += 2;
+                        while (position < headerBlock.Length && char.IsWhiteSpace(headerBlock[position]))
+                        {
+                            position++;
+                        }
+
+                        segmentStart = position;
+                        continue;
+                    }
+
+                    if (position + 1 < headerBlock.Length &&
+                        headerBlock[position] == '\r' &&
+                        headerBlock[position + 1] == ' ')
+                    {
+                        normalised ??= new StringBuilder(headerBlock.Length);
+                        normalised.Append(headerBlock, segmentStart, position - segmentStart);
+                        normalised.Append(m_CRLF);
+
+                        position += 2;
+                        segmentStart = position;
+                        continue;
+                    }
+
+                    position++;
+                }
+
+                if (normalised is null)
+                {
+                    return headerBlock;
+                }
+
+                normalised.Append(headerBlock, segmentStart, headerBlock.Length - segmentStart);
+                return normalised.ToString();
+            }
+
             // SIP headers can be extended across lines if the first character of the next line is at least on whitespace character.
-            message = Regex.Replace(message, m_CRLF + @"\s+", " ", RegexOptions.Singleline);
+            // Some user agents couldn't get the \r\n bit right; normalise those at the same time.
+            message = NormalizeFoldedHeaderLines(message);
 
-            // Some user agents couldn't get the \r\n bit right.
-            message = Regex.Replace(message, "\r ", m_CRLF, RegexOptions.Singleline);
+            var headers = new List<string>();
+            var messageSpan = message.AsSpan();
 
-            return Regex.Split(message, m_CRLF);
+            foreach (var headerRange in messageSpan.Split(m_CRLF.AsSpan()))
+            {
+                headers.Add(messageSpan[headerRange].ToString());
+            }
+
+            return headers.ToArray();
         }
 
         public static RTSPHeader ParseRTSPHeaders(string[] headersCollection)
@@ -293,7 +370,7 @@ public static RTSPHeader ParseRTSPHeaders(string[] headersCollection)
                 {
                     string headerLine = headersCollection[lineIndex];
 
-                    if (headerLine == null || headerLine.Trim().Length == 0)
+                    if (string.IsNullOrWhiteSpace(headerLine))
                     {
                         // No point processing blank headers.
                         continue;
@@ -303,16 +380,17 @@ public static RTSPHeader ParseRTSPHeaders(string[] headersCollection)
                     string headerValue = null;
 
                     // If the first character of a line is whitespace it's a continuation of the previous line.
-                    if (headerLine.StartsWith(" "))
+                    if (headerLine.StartsWith(" ", StringComparison.Ordinal))
                     {
                         headerName = lastHeader;
                         headerValue = headerLine.Trim();
                     }
                     else
                     {
-                        string[] headerParts = headerLine.Trim().Split(delimiterChars, 2);
+                        var headerLineSpan = headerLine.AsSpan().Trim();
+                        var delimiterIndex = headerLineSpan.IndexOf(':');
 
-                        if (headerParts == null || headerParts.Length < 2)
+                        if (delimiterIndex == -1)
                         {
                             logger.LogError("Invalid RTSP header, ignoring. header={HeaderLine}.", headerLine);
 
@@ -326,66 +404,64 @@ public static RTSPHeader ParseRTSPHeaders(string[] headersCollection)
                             continue;
                         }
 
-                        headerName = headerParts[0].Trim();
-                        headerValue = headerParts[1].Trim();
+                        headerName = headerLineSpan.Slice(0, delimiterIndex).Trim().ToString();
+                        headerValue = headerLineSpan.Slice(delimiterIndex + 1).Trim().ToString();
                     }
 
                     try
                     {
-                        string headerNameLower = headerName.ToLower();
-
                         #region Accept
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_ACCEPT.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_ACCEPT, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.Accept = headerValue;
                         }
                         #endregion
                         #region ContentType
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_CONTENTTYPE.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_CONTENTTYPE, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.ContentType = headerValue;
                         }
                         #endregion
                         #region ContentLength
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_CONTENTLENGTH.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_CONTENTLENGTH, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.RawCSeq = headerValue;
 
-                            if (headerValue == null || headerValue.Trim().Length == 0)
+                            if (string.IsNullOrWhiteSpace(headerValue))
                             {
-                                logger.LogWarning("Invalid RTSP header, the " + RTSPHeaders.RTSP_HEADER_CONTENTLENGTH + " was empty.");
+                                logger.LogWarning("Invalid RTSP header, the {HeaderName} was empty.", RTSPHeaders.RTSP_HEADER_CONTENTLENGTH);
                             }
                             else if (!Int32.TryParse(headerValue.Trim(), out rtspHeader.ContentLength))
                             {
-                                logger.LogWarning("Invalid RTSP header, the " + RTSPHeaders.RTSP_HEADER_CONTENTLENGTH + " was not a valid 32 bit integer, {HeaderValue}.", headerValue);
+                                logger.LogWarning("Invalid RTSP header, the {HeaderName} was not a valid 32 bit integer, {HeaderValue}.", RTSPHeaders.RTSP_HEADER_CONTENTLENGTH, headerValue);
                             }
                         }
                         #endregion
                         #region CSeq
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_CSEQ.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_CSEQ, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.RawCSeq = headerValue;
 
-                            if (headerValue == null || headerValue.Trim().Length == 0)
+                            if (string.IsNullOrWhiteSpace(headerValue))
                             {
                                 rtspHeader.CSeqParserError = RTSPHeaderParserError.CSeqEmpty;
-                                logger.LogWarning("Invalid RTSP header, the " + RTSPHeaders.RTSP_HEADER_CSEQ + " was empty.");
+                                logger.LogWarning("Invalid RTSP header, the {HeaderName} was empty.", RTSPHeaders.RTSP_HEADER_CSEQ);
                             }
                             else if (!Int32.TryParse(headerValue.Trim(), out rtspHeader.CSeq))
                             {
                                 rtspHeader.CSeqParserError = RTSPHeaderParserError.CSeqNotValidInteger;
-                                logger.LogWarning("Invalid SIP header, the " + RTSPHeaders.RTSP_HEADER_CSEQ + " was not a valid 32 bit integer, {HeaderValue}.", headerValue);
+                                logger.LogWarning("Invalid SIP header, the {HeaderName} was not a valid 32 bit integer, {HeaderValue}.", RTSPHeaders.RTSP_HEADER_CSEQ, headerValue);
                             }
                         }
                         #endregion
                         #region Session
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_SESSION.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_SESSION, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.Session = headerValue;
                         }
                         #endregion
                         #region Transport
-                        if (headerNameLower == RTSPHeaders.RTSP_HEADER_TRANSPORT.ToLower())
+                        if (string.Equals(headerName, RTSPHeaders.RTSP_HEADER_TRANSPORT, StringComparison.OrdinalIgnoreCase))
                         {
                             rtspHeader.Transport = RTSPTransportHeader.Parse(headerValue);
                         }
@@ -420,23 +496,50 @@ public static RTSPHeader ParseRTSPHeaders(string[] headersCollection)
         }
 
 
-        public new string ToString()
+        public override string ToString()
         {
             try
             {
-                StringBuilder headersBuilder = new StringBuilder();
-
-                headersBuilder.Append((CSeq > 0) ? RTSPHeaders.RTSP_HEADER_CSEQ + ": " + CSeq + m_CRLF : null);
-                headersBuilder.Append((Session != null) ? RTSPHeaders.RTSP_HEADER_SESSION + ": " + Session + m_CRLF : null);
-                headersBuilder.Append((Accept != null) ? RTSPHeaders.RTSP_HEADER_ACCEPT + ": " + Accept + m_CRLF : null);
-                headersBuilder.Append((ContentType != null) ? RTSPHeaders.RTSP_HEADER_CONTENTTYPE + ": " + ContentType + m_CRLF : null);
-                headersBuilder.Append((ContentLength != 0) ? RTSPHeaders.RTSP_HEADER_CONTENTLENGTH + ": " + ContentLength + m_CRLF : null);
-                headersBuilder.Append((Transport != null) ? RTSPHeaders.RTSP_HEADER_TRANSPORT + ": " + Transport.ToString() + m_CRLF : null);
+                var headersBuilder = new StringBuilder();
+
+                void AppendHeader<T>(string headerName, T headerValue) =>
+                    headersBuilder.Append($"{headerName}: {headerValue}{m_CRLF}");
+
+                if (CSeq > 0)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_CSEQ, CSeq);
+                }
+
+                if (Session != null)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_SESSION, Session);
+                }
+
+                if (Accept != null)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_ACCEPT, Accept);
+                }
+
+                if (ContentType != null)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_CONTENTTYPE, ContentType);
+                }
+
+                if (ContentLength != 0)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_CONTENTLENGTH, ContentLength);
+                }
+
+                if (Transport != null)
+                {
+                    AppendHeader(RTSPHeaders.RTSP_HEADER_TRANSPORT, Transport);
+                }
+
                 if (UnknownHeaders != null)
                 {
                     foreach (var unknownHeader in UnknownHeaders)
                     {
-                        headersBuilder.Append(unknownHeader + m_CRLF);
+                        headersBuilder.Append(unknownHeader).Append(m_CRLF);
                     }
                 }
 
diff --git a/src/SIPSorcery/net/RTSP/RTSPMessage.cs b/src/SIPSorcery/net/RTSP/RTSPMessage.cs
index dc90850a8..630261cd7 100644
--- a/src/SIPSorcery/net/RTSP/RTSPMessage.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPMessage.cs
@@ -97,7 +97,7 @@ public static RTSPMessage ParseRTSPMessage(string message, IPEndPoint receivedFr
                 {
                     rtspMessage.FirstLine = message.Substring(0, endFistLinePosn);
 
-                    if (rtspMessage.FirstLine.Substring(0, RTSP_RESPONSE_PREFIX.Length) == RTSP_RESPONSE_PREFIX)
+                    if (rtspMessage.FirstLine.AsSpan(0, RTSP_RESPONSE_PREFIX.Length).Equals(RTSP_RESPONSE_PREFIX, StringComparison.Ordinal))
                     {
                         rtspMessage.RTSPMessageType = RTSPMessageTypesEnum.Response;
                     }
diff --git a/src/SIPSorcery/net/RTSP/RTSPRequest.cs b/src/SIPSorcery/net/RTSP/RTSPRequest.cs
index 7ebd92b96..24742bae9 100644
--- a/src/SIPSorcery/net/RTSP/RTSPRequest.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPRequest.cs
@@ -72,13 +72,13 @@ public RTSPRequest(RTSPMethodsEnum method, string url)
                     URL = RTSPURL.ParseRTSPURL(url, out urlParserError);
                     if (urlParserError != RTSPHeaderParserError.None)
                     {
-                        throw new ApplicationException("Error parsing RTSP URL, " + urlParserError.ToString() + ".");
+                        throw new ApplicationException($"Error parsing RTSP URL, {urlParserError.ToString()}.");
                     }
                 }
             }
             catch (Exception excp)
             {
-                logger.LogError(excp, "Exception RTSPRequest Ctor. {ErrorMessage}", excp.Message + ".");
+                logger.LogError(excp, "Exception in {Method}.", nameof(RTSPRequest));
             }
         }
 
@@ -104,11 +104,9 @@ public static RTSPRequest ParseRTSPRequest(RTSPMessage rtspMessage, out RTSPRequ
             {
                 RTSPRequest rtspRequest = new RTSPRequest();
 
-                string statusLine = rtspMessage.FirstLine;
-
-                int firstSpacePosn = statusLine.IndexOf(" ");
-
-                string method = statusLine.Substring(0, firstSpacePosn).Trim();
+                var statusLine = rtspMessage.FirstLine.AsSpan();
+                var firstSpacePosn = statusLine.IndexOf(' ');
+                var method = statusLine.Slice(0, firstSpacePosn).Trim().ToString();
                 rtspRequest.Method = RTSPMethods.GetMethod(method);
                 if (rtspRequest.Method == RTSPMethodsEnum.UNKNOWN)
                 {
@@ -116,15 +114,15 @@ public static RTSPRequest ParseRTSPRequest(RTSPMessage rtspMessage, out RTSPRequ
                     logger.LogWarning("Unknown RTSP method received {Method}.", rtspRequest.Method);
                 }
 
-                statusLine = statusLine.Substring(firstSpacePosn).Trim();
-                int secondSpacePosn = statusLine.IndexOf(" ");
+                statusLine = statusLine.Slice(firstSpacePosn).Trim();
+                var secondSpacePosn = statusLine.IndexOf(' ');
 
                 if (secondSpacePosn != -1)
                 {
-                    urlStr = statusLine.Substring(0, secondSpacePosn);
+                    urlStr = statusLine.Slice(0, secondSpacePosn).ToString();
 
                     rtspRequest.URL = RTSPURL.ParseRTSPURL(urlStr);
-                    rtspRequest.RTSPVersion = statusLine.Substring(secondSpacePosn, statusLine.Length - secondSpacePosn).Trim();
+                    rtspRequest.RTSPVersion = statusLine.Slice(secondSpacePosn).Trim().ToString();
                     rtspRequest.Header = (rtspMessage.RTSPHeaders != null) ? RTSPHeader.ParseRTSPHeaders(rtspMessage.RTSPHeaders) : new RTSPHeader(0, null);
                     rtspRequest.Body = rtspMessage.Body;
 
@@ -138,23 +136,23 @@ public static RTSPRequest ParseRTSPRequest(RTSPMessage rtspMessage, out RTSPRequ
             catch (Exception excp)
             {
                 logger.LogError(excp, "Exception parsing RTSP request. URI, {Uri}. {ErrorMessage}", urlStr, excp.Message);
-                throw new ApplicationException("There was an exception parsing an RTSP request. " + excp.Message);
+                throw new ApplicationException($"There was an exception parsing an RTSP request. {excp.Message}");
             }
         }
 
-        public new string ToString()
+        public override string ToString()
         {
             try
             {
                 string methodStr = (Method != RTSPMethodsEnum.UNKNOWN) ? Method.ToString() : UnknownMethod;
-                string message = methodStr + (URL == null ? "" : (" " + URL?.ToString())) + " " + RTSPVersion + m_CRLF;
+                string message = $"{methodStr + (URL == null ? "" : ($" {URL?.ToString()}"))} {RTSPVersion}{m_CRLF}";
                 if (Header != null)
                 {
                     message += Header.ToString();
                 }
                 if (Body != null)
                 {
-                    message +=m_CRLF+ Body;
+                    message += m_CRLF + Body;
                 }
 
                 return message;
diff --git a/src/SIPSorcery/net/RTSP/RTSPResponse.cs b/src/SIPSorcery/net/RTSP/RTSPResponse.cs
index 6aeb1db24..5912681e7 100644
--- a/src/SIPSorcery/net/RTSP/RTSPResponse.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPResponse.cs
@@ -78,15 +78,14 @@ public static RTSPResponse ParseRTSPResponse(RTSPMessage rtspMessage, out RTSPRe
             {
                 RTSPResponse rtspResponse = new RTSPResponse();
 
-                string statusLine = rtspMessage.FirstLine;
+                var statusLine = rtspMessage.FirstLine.AsSpan();
+                var firstSpacePosn = statusLine.IndexOf(' ');
 
-                int firstSpacePosn = statusLine.IndexOf(" ");
-
-                rtspResponse.RTSPVersion = statusLine.Substring(0, firstSpacePosn).Trim();
-                statusLine = statusLine.Substring(firstSpacePosn).Trim();
-                rtspResponse.StatusCode = Convert.ToInt32(statusLine.Substring(0, 3));
+                rtspResponse.RTSPVersion = statusLine.Slice(0, firstSpacePosn).Trim().ToString();
+                statusLine = statusLine.Slice(firstSpacePosn).Trim();
+                rtspResponse.StatusCode = Convert.ToInt32(statusLine.Slice(0, 3).ToString());
                 rtspResponse.Status = RTSPResponseStatusCodes.GetStatusTypeForCode(rtspResponse.StatusCode);
-                rtspResponse.ReasonPhrase = statusLine.Substring(3).Trim();
+                rtspResponse.ReasonPhrase = statusLine.Slice(3).Trim().ToString();
 
                 rtspResponse.Header = RTSPHeader.ParseRTSPHeaders(rtspMessage.RTSPHeaders);
                 rtspResponse.Body = rtspMessage.Body;
@@ -96,19 +95,18 @@ public static RTSPResponse ParseRTSPResponse(RTSPMessage rtspMessage, out RTSPRe
             catch (Exception excp)
             {
                 logger.LogError(excp, "Exception parsing RTSP response. {ErrorMessage}", excp.Message);
-                throw new ApplicationException("There was an exception parsing an RTSP response. " + excp.Message);
+                throw new ApplicationException($"There was an exception parsing an RTSP response. {excp.Message}");
             }
         }
 
-        public new string ToString()
+        public override string ToString()
         {
             try
             {
-                string reasonPhrase = (!ReasonPhrase.IsNullOrBlank()) ? " " + ReasonPhrase : null;
+                string reasonPhrase = (!ReasonPhrase.IsNullOrBlank()) ? $" {ReasonPhrase}" : null;
 
-                string message =
-                    RTSPVersion + "/" + RTSPMajorVersion + "." + RTSPMinorVersion + " " + StatusCode + reasonPhrase + m_CRLF +
-                    this.Header.ToString();
+                var message =
+                    $"{RTSPVersion}/{RTSPMajorVersion}.{RTSPMinorVersion} {StatusCode}{reasonPhrase}{m_CRLF}{Header}";
 
                 if (Body != null)
                 {
diff --git a/src/SIPSorcery/net/RTSP/RTSPURL.cs b/src/SIPSorcery/net/RTSP/RTSPURL.cs
index 4547f7c57..4ce2cf582 100644
--- a/src/SIPSorcery/net/RTSP/RTSPURL.cs
+++ b/src/SIPSorcery/net/RTSP/RTSPURL.cs
@@ -73,7 +73,7 @@ public static RTSPURL ParseRTSPURL(string url, out RTSPHeaderParserError parserE
 
                 RTSPURL rtspURL = new RTSPURL();
 
-                if (url == null || url.Trim().Length == 0)
+                if (string.IsNullOrWhiteSpace(url))
                 {
                     throw new ApplicationException("An RTSP URI cannot be parsed from an empty string.");
                 }
@@ -112,11 +112,11 @@ public static RTSPURL ParseRTSPURL(string url, out RTSPHeaderParserError parserE
             }
             catch (Exception excp)
             {
-                throw new ApplicationException("There was an exception parsing an RTSP URL. " + excp.Message + " url=" + url);
+                throw new ApplicationException($"There was an exception parsing an RTSP URL. {excp.Message} url={url}");
             }
         }
 
-        public new string ToString()
+        public override string ToString()
         {
             try
             {
diff --git a/src/SIPSorcery/net/SCTP/Chunks/SctpTlvChunkParameter.cs b/src/SIPSorcery/net/SCTP/Chunks/SctpTlvChunkParameter.cs
index 0e86a5c3e..094bf53e3 100644
--- a/src/SIPSorcery/net/SCTP/Chunks/SctpTlvChunkParameter.cs
+++ b/src/SIPSorcery/net/SCTP/Chunks/SctpTlvChunkParameter.cs
@@ -211,8 +211,7 @@ public ushort ParseFirstWord(byte[] buffer, int posn)
                 // The buffer was not big enough to supply the specified chunk parameter.
                 int bytesRequired = paramLen;
                 int bytesAvailable = buffer.Length - posn;
-                throw new ApplicationException($"The SCTP chunk parameter buffer was too short. " +
-                    $"Required {bytesRequired} bytes but only {bytesAvailable} available.");
+                throw new ApplicationException($"The SCTP chunk parameter buffer was too short. Required {bytesRequired} bytes but only {bytesAvailable} available.");
             }
 
             return paramLen;
diff --git a/src/SIPSorcery/net/SCTP/SctpAssociation.cs b/src/SIPSorcery/net/SCTP/SctpAssociation.cs
index 21e4d0c38..ad6069ca4 100644
--- a/src/SIPSorcery/net/SCTP/SctpAssociation.cs
+++ b/src/SIPSorcery/net/SCTP/SctpAssociation.cs
@@ -400,13 +400,13 @@ internal void OnPacketReceived(SctpPacket packet)
                             OnAbortReceived?.Invoke(abortReason);
                             break;
 
-                        case var ct when ct == SctpChunkType.COOKIE_ACK && State != SctpAssociationState.CookieEchoed:
+                        case var _ when chunkType == SctpChunkType.COOKIE_ACK && State != SctpAssociationState.CookieEchoed:
                             // https://tools.ietf.org/html/rfc4960#section-5.2.5
                             // At any state other than COOKIE-ECHOED, an endpoint should silently
                             // discard a received COOKIE ACK chunk.
                             break;
 
-                        case var ct when ct == SctpChunkType.COOKIE_ACK && State == SctpAssociationState.CookieEchoed:
+                        case var _ when chunkType == SctpChunkType.COOKIE_ACK && State == SctpAssociationState.CookieEchoed:
                             SetState(SctpAssociationState.Established);
                             CancelTimers();
                             _dataSender.StartSending();
@@ -468,13 +468,13 @@ internal void OnPacketReceived(SctpPacket packet)
                             SendChunk(chunk);
                             break;
 
-                        case var ct when ct == SctpChunkType.INIT_ACK && State != SctpAssociationState.CookieWait:
+                        case var _ when chunkType == SctpChunkType.INIT_ACK && State != SctpAssociationState.CookieWait:
                             // https://tools.ietf.org/html/rfc4960#section-5.2.3
                             // If an INIT ACK is received by an endpoint in any state other than the
                             // COOKIE - WAIT state, the endpoint should discard the INIT ACK chunk.
                             break;
 
-                        case var ct when ct == SctpChunkType.INIT_ACK && State == SctpAssociationState.CookieWait:
+                        case var _ when chunkType == SctpChunkType.INIT_ACK && State == SctpAssociationState.CookieWait:
 
                             if (_t1Init != null)
                             {
@@ -528,7 +528,7 @@ internal void OnPacketReceived(SctpPacket packet)
                             }
                             break;
 
-                        case var ct when ct == SctpChunkType.INIT_ACK && State != SctpAssociationState.CookieWait:
+                        case var _ when chunkType == SctpChunkType.INIT_ACK && State != SctpAssociationState.CookieWait:
                             logger.LogWarning("SCTP association received INIT_ACK chunk in wrong state of {State}, ignoring.", State);
                             break;
 
@@ -536,7 +536,7 @@ internal void OnPacketReceived(SctpPacket packet)
                             _dataSender.GotSack(chunk as SctpSackChunk);
                             break;
 
-                        case var ct when ct == SctpChunkType.SHUTDOWN && State == SctpAssociationState.Established:
+                        case var _ when chunkType == SctpChunkType.SHUTDOWN && State == SctpAssociationState.Established:
                             // TODO: Check outstanding data chunks.
                             _dataSender?.Close();
                             var shutdownAck = new SctpChunk(SctpChunkType.SHUTDOWN_ACK);
@@ -544,7 +544,7 @@ internal void OnPacketReceived(SctpPacket packet)
                             SetState(SctpAssociationState.ShutdownAckSent);
                             break;
 
-                        case var ct when ct == SctpChunkType.SHUTDOWN_ACK && State == SctpAssociationState.ShutdownSent:
+                        case var _ when chunkType == SctpChunkType.SHUTDOWN_ACK && State == SctpAssociationState.ShutdownSent:
                             SetState(SctpAssociationState.Closed);
                             var shutCompleteChunk = new SctpChunk(SctpChunkType.SHUTDOWN_COMPLETE,
                                 (byte)(_remoteVerificationTag != 0 ? SHUTDOWN_CHUNK_TBIT_FLAG : 0x00));
diff --git a/src/SIPSorcery/net/SDP/SDP.cs b/src/SIPSorcery/net/SDP/SDP.cs
index 700328a01..9c32ea8a8 100644
--- a/src/SIPSorcery/net/SDP/SDP.cs
+++ b/src/SIPSorcery/net/SDP/SDP.cs
@@ -102,12 +102,14 @@
 //-----------------------------------------------------------------------------
 
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
-using System.Text.RegularExpressions;
+using System.Text;
 using Microsoft.Extensions.Logging;
+using Polyfills;
 using SIPSorcery.Sys;
 
 namespace SIPSorcery.Net
@@ -153,7 +155,7 @@ public class SDP
         public string AddressOrHost;         // IP Address or Host of the machine that created the session, either FQDN or dotted quad or textual for IPv6.
         public string Owner
         {
-            get { return Username + " " + SessionId + " " + AnnouncementVersion + " " + NetworkType + " " + AddressType + " " + AddressOrHost; }
+            get { return $"{Username} {SessionId} {AnnouncementVersion} {NetworkType} {AddressType} {AddressOrHost}"; }
         }
 
         public string SessionName = "sipsorcery";            // Common name of the session.
@@ -205,7 +207,7 @@ public static SDP ParseSDPDescription(string sdpDescription)
         {
             try
             {
-                if (sdpDescription != null && sdpDescription.Trim().Length > 0)
+                if (!string.IsNullOrWhiteSpace(sdpDescription))
                 {
                     SDP sdp = new SDP();
                     sdp.m_rawSdp = sdpDescription;
@@ -216,580 +218,812 @@ public static SDP ParseSDPDescription(string sdpDescription)
                     // in this dictionary. A dynamic media format type cannot be created without an rtpmap.
                     Dictionary<int, string> _pendingFmtp = new Dictionary<int, string>();
 
-                    //string[] sdpLines = Regex.Split(sdpDescription, CRLF);
-                    string[] sdpLines = sdpDescription.Split(new string[] { "\r\n", "\r", "\n" }, StringSplitOptions.RemoveEmptyEntries);
+                    var sdpDescriptionSpan = sdpDescription.AsSpan();
+                    Span<Range> ownerFieldRanges = stackalloc Range[6];
+                    const StringSplitOptions TrimEntries = (StringSplitOptions)2;
+                    const StringSplitOptions RemoveEmptyAndTrimSplitOptions = StringSplitOptions.RemoveEmptyEntries | TrimEntries;
 
-                    foreach (string sdpLine in sdpLines)
+                    static bool StartsWithAttribute(ReadOnlySpan<char> line, string attributePrefix) =>
+                        line.StartsWith("a=", StringComparison.Ordinal) &&
+                        line.Slice(2).StartsWith(attributePrefix, StringComparison.Ordinal);
+
+                    static bool EqualsAttribute(ReadOnlySpan<char> line, string attribute) =>
+                        line.Length == attribute.Length + 2 &&
+                        line.StartsWith("a=", StringComparison.Ordinal) &&
+                        line.Slice(2).Equals(attribute.AsSpan(), StringComparison.Ordinal);
+
+                    static ReadOnlySpan<char> SliceAfterColon(ReadOnlySpan<char> line) =>
+                        line.Slice(line.IndexOf(':') + 1);
+
+                    static bool TryReadToken(ReadOnlySpan<char> value, ref int offset, out int tokenStart, out int tokenLength)
+                    {
+                        while (offset < value.Length && char.IsWhiteSpace(value[offset]))
+                        {
+                            offset++;
+                        }
+
+                        if (offset == value.Length)
+                        {
+                            tokenStart = 0;
+                            tokenLength = 0;
+                            return false;
+                        }
+
+                        tokenStart = offset;
+                        var endIndex = offset;
+                        while (endIndex < value.Length && !char.IsWhiteSpace(value[endIndex]))
+                        {
+                            endIndex++;
+                        }
+
+                        tokenLength = endIndex - tokenStart;
+                        offset = endIndex;
+                        return true;
+                    }
+
+                    static bool TrySplitAttributeValue(
+                        ReadOnlySpan<char> line,
+                        int prefixLength,
+                        out int idStart,
+                        out int idLength,
+                        out int attributeStart)
                     {
-                        string sdpLineTrimmed = sdpLine.Trim();
+                        var offset = prefixLength;
+                        if (!TryReadToken(line, ref offset, out idStart, out idLength))
+                        {
+                            attributeStart = 0;
+                            return false;
+                        }
+
+                        while (offset < line.Length && char.IsWhiteSpace(line[offset]))
+                        {
+                            offset++;
+                        }
 
-                        switch (sdpLineTrimmed)
+                        attributeStart = offset;
+                        return attributeStart < line.Length;
+                    }
+
+                    static bool TryParseMediaLine(
+                        ReadOnlySpan<char> mediaLine,
+                        out int mediaTypeStart,
+                        out int mediaTypeLength,
+                        out int port,
+                        out int? portCount,
+                        out int transportStart,
+                        out int transportLength,
+                        out int formatsStart)
+                    {
+                        mediaTypeStart = 0;
+                        mediaTypeLength = 0;
+                        port = 0;
+                        portCount = null;
+                        transportStart = 0;
+                        transportLength = 0;
+                        formatsStart = 0;
+
+                        var offset = 0;
+                        if (!TryReadToken(mediaLine, ref offset, out mediaTypeStart, out mediaTypeLength) ||
+                            !TryReadToken(mediaLine, ref offset, out var portStart, out var portLength) ||
+                            !TryReadToken(mediaLine, ref offset, out transportStart, out transportLength))
+                        {
+                            return false;
+                        }
+
+                        var portToken = mediaLine.Slice(portStart, portLength);
+                        var slashIndex = portToken.IndexOf('/');
+                        var portSpan = slashIndex == -1 ? portToken : portToken.Slice(0, slashIndex);
+                        if (!int.TryParse(portSpan, out port))
+                        {
+                            return false;
+                        }
+
+                        if (slashIndex != -1)
+                        {
+                            var portCountSpan = portToken.Slice(slashIndex + 1);
+                            if (portCountSpan.IsEmpty || !int.TryParse(portCountSpan, out var parsedPortCount))
+                            {
+                                return false;
+                            }
+
+                            portCount = parsedPortCount;
+                        }
+
+                        while (offset < mediaLine.Length && char.IsWhiteSpace(mediaLine[offset]))
+                        {
+                            offset++;
+                        }
+
+                        formatsStart = offset;
+                        return true;
+                    }
+
+                    static bool TryParseExtensionMap(ReadOnlySpan<char> line, out int id, out int uriStart, out int uriLength)
+                    {
+                        id = 0;
+                        uriStart = 0;
+                        uriLength = 0;
+                        var offset = SDPMediaAnnouncement.MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX.Length;
+
+                        if (!TryReadToken(line, ref offset, out var idStart, out var idLength) ||
+                            !int.TryParse(line.Slice(idStart, idLength), out id) ||
+                            !TryReadToken(line, ref offset, out uriStart, out uriLength))
                         {
-                            case var l when l.StartsWith("v="):
-                                if (!Decimal.TryParse(sdpLineTrimmed.Substring(2), out sdp.Version))
-                                {
-                                    logger.LogWarning("The Version value in an SDP description could not be parsed as a decimal: {sdpLine}.", sdpLine);
-                                }
-                                break;
-
-                            case var l when l.StartsWith("o="):
-                                var ownerFields = sdpLineTrimmed.Substring(2).Split(new []{' '}, 6, StringSplitOptions.RemoveEmptyEntries);
-
-                                if (ownerFields.Length >= 5)
-                                {
-                                    sdp.Username = ownerFields[0];
-                                    sdp.SessionId = ownerFields[1];
-                                    sdp.AnnouncementVersion = UInt64.TryParse(ownerFields[2], out var version) ? version : 0;
-                                    sdp.NetworkType = ownerFields[3];
-                                    sdp.AddressType = ownerFields[4];
-                                    sdp.AddressOrHost = ownerFields.ElementAtOrDefault(5); // Safely handle missing elements
-                                }
-                                else
-                                {
-                                    logger.LogWarning("The SDP message had an invalid SDP line format for 'o=': {sdpLineTrimmed}", sdpLineTrimmed);
-                                }
-                                break;
-
-                            case var l when l.StartsWith("s="):
-                                sdp.SessionName = sdpLineTrimmed.Substring(2);
-                                break;
-
-                            case var l when l.StartsWith("i="):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.MediaDescription = sdpLineTrimmed.Substring(2);
-                                }
-                                else
-                                {
-                                    sdp.SessionDescription = sdpLineTrimmed.Substring(2);
-                                }
-
-                                break;
-
-                            case var l when l.StartsWith("c="):
-
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.Connection = SDPConnectionInformation.ParseConnectionInformation(sdpLineTrimmed);
-                                }
-                                else if (sdp.Connection == null)
-                                {
-                                    sdp.Connection = SDPConnectionInformation.ParseConnectionInformation(sdpLineTrimmed);
-                                }
-                                else
-                                {
-                                    logger.LogWarning("The SDP message had a duplicate connection attribute which was ignored.");
-                                }
-
-                                break;
-
-                            case var l when l.StartsWith("b="):
-                                if (activeAnnouncement != null)
-                                {
-                                    if (l.StartsWith(SDPMediaAnnouncement.TIAS_BANDWIDTH_ATTRIBUE_PREFIX))
-                                    {
-                                        if (uint.TryParse(l.Substring(l.IndexOf(':') + 1), out uint tias))
+                            return false;
+                        }
+
+                        while (offset < line.Length && char.IsWhiteSpace(line[offset]))
+                        {
+                            offset++;
+                        }
+
+                        return offset == line.Length;
+                    }
+
+                    static bool TryParseMediaStreamStatus(ReadOnlySpan<char> attribute, out MediaStreamStatusEnum mediaStreamStatus)
+                    {
+                        mediaStreamStatus = MediaStreamStatusEnum.SendRecv;
+
+                        if (attribute.Equals(MediaStreamStatusType.SEND_RECV_ATTRIBUTE.AsSpan(), StringComparison.OrdinalIgnoreCase))
+                        {
+                            mediaStreamStatus = MediaStreamStatusEnum.SendRecv;
+                            return true;
+                        }
+
+                        if (attribute.Equals(MediaStreamStatusType.SEND_ONLY_ATTRIBUTE.AsSpan(), StringComparison.OrdinalIgnoreCase))
+                        {
+                            mediaStreamStatus = MediaStreamStatusEnum.SendOnly;
+                            return true;
+                        }
+
+                        if (attribute.Equals(MediaStreamStatusType.RECV_ONLY_ATTRIBUTE.AsSpan(), StringComparison.OrdinalIgnoreCase))
+                        {
+                            mediaStreamStatus = MediaStreamStatusEnum.RecvOnly;
+                            return true;
+                        }
+
+                        if (attribute.Equals(MediaStreamStatusType.INACTIVE_ATTRIBUTE.AsSpan(), StringComparison.OrdinalIgnoreCase))
+                        {
+                            mediaStreamStatus = MediaStreamStatusEnum.Inactive;
+                            return true;
+                        }
+
+                        return false;
+                    }
+
+                    var sdpLineRangeBuffer = ArrayPool<Range>.Shared.Rent(sdpDescriptionSpan.Length + 1);
+                    try
+                    {
+                        var sdpLineRanges = sdpLineRangeBuffer.AsSpan(0, sdpDescriptionSpan.Length + 1);
+                        var sdpLineCount = sdpDescriptionSpan.SplitAny(
+                            sdpLineRanges,
+                            "\r\n".AsSpan(),
+                            RemoveEmptyAndTrimSplitOptions);
+
+                        for (var sdpLineIndex = 0; sdpLineIndex < sdpLineCount; sdpLineIndex++)
+                        {
+                            var sdpLineTrimmedSpan = sdpDescriptionSpan[sdpLineRanges[sdpLineIndex]];
+
+                            switch (sdpLineTrimmedSpan)
+                            {
+                                case var _ when sdpLineTrimmedSpan.StartsWith("v=", StringComparison.Ordinal):
+                                    if (!Decimal.TryParse(sdpLineTrimmedSpan.Slice(2), out sdp.Version))
+                                    {
+                                        logger.LogWarning("The Version value in an SDP description could not be parsed as a decimal: {sdpLine}.", sdpLineTrimmedSpan.ToString());
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("o=", StringComparison.Ordinal):
+                                    var ownerFieldsSpan = sdpLineTrimmedSpan.Slice(2);
+                                    var ownerFieldCount = ownerFieldsSpan.Split(ownerFieldRanges, ' ', StringSplitOptions.RemoveEmptyEntries);
+
+                                    if (ownerFieldCount >= 5)
+                                    {
+                                        sdp.Username = ownerFieldsSpan[ownerFieldRanges[0]].ToString();
+                                        sdp.SessionId = ownerFieldsSpan[ownerFieldRanges[1]].ToString();
+                                        sdp.AnnouncementVersion = UInt64.TryParse(ownerFieldsSpan[ownerFieldRanges[2]].ToString(), out var version) ? version : 0;
+                                        sdp.NetworkType = ownerFieldsSpan[ownerFieldRanges[3]].ToString();
+                                        sdp.AddressType = ownerFieldsSpan[ownerFieldRanges[4]].ToString();
+                                        sdp.AddressOrHost = ownerFieldCount > 5 ? ownerFieldsSpan[ownerFieldRanges[5]].ToString() : null;
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("The SDP message had an invalid SDP line format for 'o=': {sdpLineTrimmed}", sdpLineTrimmedSpan.ToString());
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("s=", StringComparison.Ordinal):
+                                    sdp.SessionName = sdpLineTrimmedSpan.Slice(2).ToString();
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("i=", StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.MediaDescription = sdpLineTrimmedSpan.Slice(2).ToString();
+                                    }
+                                    else
+                                    {
+                                        sdp.SessionDescription = sdpLineTrimmedSpan.Slice(2).ToString();
+                                    }
+
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("c=", StringComparison.Ordinal):
+
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.Connection = SDPConnectionInformation.ParseConnectionInformation(sdpLineTrimmedSpan.ToString());
+                                    }
+                                    else if (sdp.Connection == null)
+                                    {
+                                        sdp.Connection = SDPConnectionInformation.ParseConnectionInformation(sdpLineTrimmedSpan.ToString());
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("The SDP message had a duplicate connection attribute which was ignored.");
+                                    }
+
+                                    break;
+
+                                case var l when l.StartsWith("b=", StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        if (l.StartsWith(SDPMediaAnnouncement.TIAS_BANDWIDTH_ATTRIBUE_PREFIX, StringComparison.Ordinal))
                                         {
-                                            activeAnnouncement.TIASBandwidth = tias;
+                                            if (uint.TryParse(SliceAfterColon(l), out var tias))
+                                            {
+                                                activeAnnouncement.TIASBandwidth = tias;
+                                            }
+                                        }
+                                        else
+                                        {
+                                            activeAnnouncement.BandwidthAttributes.Add(sdpLineTrimmedSpan.Slice(2).ToString());
                                         }
                                     }
                                     else
                                     {
-                                        activeAnnouncement.BandwidthAttributes.Add(sdpLineTrimmed.Substring(2));
-                                    }
-                                }
-                                else
-                                {
-                                    sdp.BandwidthAttributes.Add(sdpLineTrimmed.Substring(2));
-                                }
-                                break;
-
-                            case var l when l.StartsWith("t="):
-                                sdp.Timing = sdpLineTrimmed.Substring(2);
-                                break;
-
-                            case var l when l.StartsWith("m="):
-                                Match mediaMatch = Regex.Match(
-                                        sdpLineTrimmed.Substring(2),
-                                        @"(?<type>\w+)\s+(?<port>\d+)(?:\/(?<portCount>\d+))?\s+(?<transport>\S+)\s*(?<formats>.*)$"
-                                    );
-                                if (mediaMatch.Success)
-                                {
-                                    SDPMediaAnnouncement announcement = new SDPMediaAnnouncement();
-                                    announcement.MLineIndex = mLineIndex;
-                                    announcement.Media = SDPMediaTypes.GetSDPMediaType(mediaMatch.Result("${type}"));
-
-                                    // Parse the primary port.
-                                    int.TryParse(mediaMatch.Result("${port}"), out announcement.Port);
-                                    if (mediaMatch.Groups["portCount"].Success)
-                                    {
-                                        int portCount;
-                                        if (Int32.TryParse(mediaMatch.Result("${portCount}"), out portCount))
+                                        sdp.BandwidthAttributes.Add(sdpLineTrimmedSpan.Slice(2).ToString());
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("t=", StringComparison.Ordinal):
+                                    sdp.Timing = sdpLineTrimmedSpan.Slice(2).ToString();
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith("m=", StringComparison.Ordinal):
+                                    var mediaLine = sdpLineTrimmedSpan.Slice(2);
+                                    if (TryParseMediaLine(
+                                        mediaLine,
+                                        out var mediaTypeStart,
+                                        out var mediaTypeLength,
+                                        out var port,
+                                        out var portCount,
+                                        out var transportStart,
+                                        out var transportLength,
+                                        out var formatsStart))
+                                    {
+                                        var announcement = new SDPMediaAnnouncement();
+                                        announcement.MLineIndex = mLineIndex;
+                                        announcement.Media = SDPMediaTypes.GetSDPMediaType(mediaLine.Slice(mediaTypeStart, mediaTypeLength).ToString());
+
+                                        // Parse the primary port.
+                                        announcement.Port = port;
+                                        if (portCount.HasValue)
                                         {
-                                            announcement.PortCount = portCount;
+                                            announcement.PortCount = portCount.Value;
                                         }
+
+                                        announcement.Transport = mediaLine.Slice(transportStart, transportLength).ToString();
+                                        announcement.ParseMediaFormats(mediaLine.Slice(formatsStart).ToString());
+                                        if (announcement.Media == SDPMediaTypesEnum.audio || announcement.Media == SDPMediaTypesEnum.video || announcement.Media == SDPMediaTypesEnum.text)
+                                        {
+                                            announcement.MediaStreamStatus = sdp.SessionMediaStreamStatus != null ? sdp.SessionMediaStreamStatus.Value :
+                                                MediaStreamStatusEnum.SendRecv;
+                                        }
+                                        sdp.Media.Add(announcement);
+
+                                        activeAnnouncement = announcement;
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("A media line in SDP was invalid: {sdpLine}.", sdpLineTrimmedSpan.Slice(2).ToString());
+                                    }
+
+                                    mLineIndex++;
+                                    break;
+
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, GROUP_ATRIBUTE_PREFIX):
+                                    sdp.Group = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    break;
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, ICE_LITE_IMPLEMENTATION_ATTRIBUTE_PREFIX):
+                                    sdp.IceImplementation = IceImplementationEnum.lite;
+                                    break;
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, ICE_UFRAG_ATTRIBUTE_PREFIX):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.IceUfrag = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
+                                    else
+                                    {
+                                        sdp.IceUfrag = SliceAfterColon(sdpLineTrimmedSpan).ToString();
                                     }
+                                    break;
 
-                                    announcement.Transport = mediaMatch.Result("${transport}");
-                                    announcement.ParseMediaFormats(mediaMatch.Result("${formats}"));
-                                    if (announcement.Media == SDPMediaTypesEnum.audio || announcement.Media == SDPMediaTypesEnum.video || announcement.Media == SDPMediaTypesEnum.text)
-                                    {
-                                        announcement.MediaStreamStatus = sdp.SessionMediaStreamStatus != null ? sdp.SessionMediaStreamStatus.Value :
-                                            MediaStreamStatusEnum.SendRecv;
-                                    }
-                                    sdp.Media.Add(announcement);
-
-                                    activeAnnouncement = announcement;
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A media line in SDP was invalid: {sdpLine}.", sdpLineTrimmed.Substring(2));
-                                }
-
-                                mLineIndex++;
-                                break;
-
-                            case var x when x.StartsWith($"a={GROUP_ATRIBUTE_PREFIX}"):
-                                sdp.Group = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                break;
-                            case var x when x.StartsWith($"a={ICE_LITE_IMPLEMENTATION_ATTRIBUTE_PREFIX}"):
-                                sdp.IceImplementation = IceImplementationEnum.lite;
-                                break;
-                            case var x when x.StartsWith($"a={ICE_UFRAG_ATTRIBUTE_PREFIX}"):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.IceUfrag = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                else
-                                {
-                                    sdp.IceUfrag = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                break;
-
-                            case var x when x.StartsWith($"a={ICE_PWD_ATTRIBUTE_PREFIX}"):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.IcePwd = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                else
-                                {
-                                    sdp.IcePwd = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                break;
-
-                            case var x when x.StartsWith($"a={ICE_SETUP_ATTRIBUTE_PREFIX}"):
-                                int colonIndex = sdpLineTrimmed.IndexOf(':');
-                                if (colonIndex != -1 && sdpLineTrimmed.Length > colonIndex)
-                                {
-                                    string iceRoleStr = sdpLineTrimmed.Substring(colonIndex + 1).Trim();
-                                    if (Enum.TryParse<IceRolesEnum>(iceRoleStr, true, out var iceRole))
-                                    {
-                                        if (activeAnnouncement != null)
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, ICE_PWD_ATTRIBUTE_PREFIX):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.IcePwd = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
+                                    else
+                                    {
+                                        sdp.IcePwd = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
+                                    break;
+
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, ICE_SETUP_ATTRIBUTE_PREFIX):
+                                    var colonIndex = sdpLineTrimmedSpan.IndexOf(':');
+                                    if (colonIndex != -1 && sdpLineTrimmedSpan.Length > colonIndex)
+                                    {
+                                        var iceRoleStr = sdpLineTrimmedSpan.Slice(colonIndex + 1).Trim().ToString();
+                                        if (Enum.TryParse<IceRolesEnum>(iceRoleStr, true, out var iceRole))
                                         {
-                                            activeAnnouncement.IceRole = iceRole;
+                                            if (activeAnnouncement != null)
+                                            {
+                                                activeAnnouncement.IceRole = iceRole;
+                                            }
+                                            else
+                                            {
+                                                sdp.IceRole = iceRole;
+                                            }
                                         }
                                         else
                                         {
-                                            sdp.IceRole = iceRole;
+                                            logger.LogWarning("ICE role was not recognised from SDP attribute: {sdpLineTrimmed}.", sdpLineTrimmedSpan.ToString());
                                         }
                                     }
                                     else
                                     {
-                                        logger.LogWarning("ICE role was not recognised from SDP attribute: {sdpLineTrimmed}.", sdpLineTrimmed);
-                                    }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("ICE role SDP attribute was missing the mandatory colon: {sdpLineTrimmed}.", sdpLineTrimmed);
-                                }
-                                break;
-
-                            case var x when x.StartsWith($"a={DTLS_FINGERPRINT_ATTRIBUTE_PREFIX}"):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.DtlsFingerprint = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                else
-                                {
-                                    sdp.DtlsFingerprint = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                break;
-
-                            case var x when x.StartsWith($"a={ICE_CANDIDATE_ATTRIBUTE_PREFIX}"):
-                                if (activeAnnouncement != null)
-                                {
-                                    if (activeAnnouncement.IceCandidates == null)
-                                    {
-                                        activeAnnouncement.IceCandidates = new List<string>();
-                                    }
-                                    activeAnnouncement.IceCandidates.Add(sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1));
-                                }
-                                else
-                                {
-                                    if (sdp.IceCandidates == null)
-                                    {
-                                        sdp.IceCandidates = new List<string>();
-                                    }
-                                    sdp.IceCandidates.Add(sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1));
-                                }
-                                break;
-
-                            case var x when x == $"a={END_ICE_CANDIDATES_ATTRIBUTE}":
-                                // TODO: Set a flag.
-                                break;
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null) {
-                                    if (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video) {
-                                         var formatAttributeMatch = Regex.Match(sdpLineTrimmed, SDPMediaAnnouncement.MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX + @"(?<id>\d+) (?<url>\S+)$");
-                                         if (formatAttributeMatch.Success) {
-                                             var extensionId = formatAttributeMatch.Result("${id}");
-                                             var uri = formatAttributeMatch.Result("${url}");
-                                             if (Int32.TryParse(extensionId, out var id)) {
-                                                var rtpExtension = RTPHeaderExtension.GetRTPHeaderExtension(id, uri, activeAnnouncement.Media);
-                                                if ( (rtpExtension != null) && !activeAnnouncement.HeaderExtensions.ContainsKey(id))
-                                                {
-                                                    activeAnnouncement.HeaderExtensions.Add(id, rtpExtension);
-                                                }
-                                             }
-                                             else {
-                                                 logger.LogWarning("Invalid id of header extension in " + SDPMediaAnnouncement.MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX);
-                                             }
-                                         }
-                                    }
-                                }
-
-                                break;
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    if (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video || activeAnnouncement.Media == SDPMediaTypesEnum.text)
-                                    {
-                                        // Parse the rtpmap attribute for audio/video announcements.
-                                        Match formatAttributeMatch = Regex.Match(sdpLineTrimmed, SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX + @"(?<id>\d+)\s+(?<attribute>.*)$");
-                                        if (formatAttributeMatch.Success)
+                                        logger.LogWarning("ICE role SDP attribute was missing the mandatory colon: {sdpLineTrimmed}.", sdpLineTrimmedSpan.ToString());
+                                    }
+                                    break;
+
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, DTLS_FINGERPRINT_ATTRIBUTE_PREFIX):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.DtlsFingerprint = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
+                                    else
+                                    {
+                                        sdp.DtlsFingerprint = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
+                                    break;
+
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, ICE_CANDIDATE_ATTRIBUTE_PREFIX):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        if (activeAnnouncement.IceCandidates == null)
+                                        {
+                                            activeAnnouncement.IceCandidates = new List<string>();
+                                        }
+                                        activeAnnouncement.IceCandidates.Add(SliceAfterColon(sdpLineTrimmedSpan).ToString());
+                                    }
+                                    else
+                                    {
+                                        if (sdp.IceCandidates == null)
                                         {
-                                            string formatID = formatAttributeMatch.Result("${id}");
-                                            string rtpmap = formatAttributeMatch.Result("${attribute}");
+                                            sdp.IceCandidates = new List<string>();
+                                        }
+                                        sdp.IceCandidates.Add(SliceAfterColon(sdpLineTrimmedSpan).ToString());
+                                    }
+                                    break;
+
+                                case var _ when EqualsAttribute(sdpLineTrimmedSpan, END_ICE_CANDIDATES_ATTRIBUTE):
+                                    // TODO: Set a flag.
+                                    break;
+                                case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null &&
+                                        (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video) &&
+                                        TryParseExtensionMap(l, out var extensionId, out var uriStart, out var uriLength))
+                                    {
+                                        var rtpExtension = RTPHeaderExtension.GetRTPHeaderExtension(extensionId, l.Slice(uriStart, uriLength).ToString(), activeAnnouncement.Media);
+                                        if ((rtpExtension != null) && !activeAnnouncement.HeaderExtensions.ContainsKey(extensionId))
+                                        {
+                                            activeAnnouncement.HeaderExtensions.Add(extensionId, rtpExtension);
+                                        }
+                                    }
 
-                                            if (Int32.TryParse(formatID, out int id))
+                                    break;
+                                case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        if (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video || activeAnnouncement.Media == SDPMediaTypesEnum.text)
+                                        {
+                                            // Parse the rtpmap attribute for audio/video announcements.
+                                            if (TrySplitAttributeValue(
+                                               l,
+                                               SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX.Length,
+                                               out var formatIDStart,
+                                               out var formatIDLength,
+                                               out var rtpmapStart))
                                             {
-                                                if (activeAnnouncement.MediaFormats.ContainsKey(id))
+                                                var formatID = l.Slice(formatIDStart, formatIDLength);
+                                                if (int.TryParse(formatID, out var mediaFormatId))
                                                 {
-                                                    activeAnnouncement.MediaFormats[id] = activeAnnouncement.MediaFormats[id].WithUpdatedRtpmap(rtpmap);
+                                                    var rtpmap = l.Slice(rtpmapStart).ToString();
+                                                    if (activeAnnouncement.MediaFormats.ContainsKey(mediaFormatId))
+                                                    {
+                                                        activeAnnouncement.MediaFormats[mediaFormatId] = activeAnnouncement.MediaFormats[mediaFormatId].WithUpdatedRtpmap(rtpmap);
+                                                    }
+                                                    else
+                                                    {
+                                                        var fmtp = _pendingFmtp.ContainsKey(mediaFormatId) ? _pendingFmtp[mediaFormatId] : null;
+                                                        activeAnnouncement.MediaFormats.Add(mediaFormatId, new SDPAudioVideoMediaFormat(activeAnnouncement.Media, mediaFormatId, rtpmap, fmtp));
+                                                    }
                                                 }
                                                 else
                                                 {
-                                                    string fmtp = _pendingFmtp.ContainsKey(id) ? _pendingFmtp[id] : null;
-                                                    activeAnnouncement.MediaFormats.Add(id, new SDPAudioVideoMediaFormat(activeAnnouncement.Media, id, rtpmap, fmtp));
+                                                    logger.LogWarning("Non-numeric audio/video media format attribute in SDP: {sdpLine}", sdpLineTrimmedSpan.ToString());
                                                 }
                                             }
                                             else
                                             {
-                                                logger.LogWarning("Non-numeric audio/video media format attribute in SDP: {sdpLine}", sdpLine);
+                                                activeAnnouncement.AddExtra(sdpLineTrimmedSpan.ToString());
                                             }
                                         }
                                         else
                                         {
-                                            activeAnnouncement.AddExtra(sdpLineTrimmed);
+                                            // Parse the rtpmap attribute for NON audio/video announcements.
+                                            if (TrySplitAttributeValue(
+                                                l,
+                                                SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX.Length,
+                                                out var formatIDStart,
+                                                out var formatIDLength,
+                                                out var rtpmapStart))
+                                            {
+                                                var formatID = l.Slice(formatIDStart, formatIDLength).ToString();
+                                                var rtpmap = l.Slice(rtpmapStart).ToString();
+
+                                                if (activeAnnouncement.ApplicationMediaFormats.ContainsKey(formatID))
+                                                {
+                                                    activeAnnouncement.ApplicationMediaFormats[formatID] = activeAnnouncement.ApplicationMediaFormats[formatID].WithUpdatedRtpmap(rtpmap);
+                                                }
+                                                else
+                                                {
+                                                    activeAnnouncement.ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID, rtpmap, null));
+                                                }
+                                            }
+                                            else
+                                            {
+                                                activeAnnouncement.AddExtra(sdpLineTrimmedSpan.ToString());
+                                            }
                                         }
                                     }
                                     else
                                     {
-                                        // Parse the rtpmap attribute for NON audio/video announcements.
-                                        Match formatAttributeMatch = Regex.Match(sdpLineTrimmed, SDPMediaAnnouncement.MEDIA_FORMAT_ATTRIBUTE_PREFIX + @"(?<id>\S+)\s+(?<attribute>.*)$");
-                                        if (formatAttributeMatch.Success)
-                                        {
-                                            string formatID = formatAttributeMatch.Result("${id}");
-                                            string rtpmap = formatAttributeMatch.Result("${attribute}");
+                                        logger.LogWarning("There was no active media announcement for a media format attribute, ignoring.");
+                                    }
+                                    break;
 
-                                            if (activeAnnouncement.ApplicationMediaFormats.ContainsKey(formatID))
+                                case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        if (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video || activeAnnouncement.Media == SDPMediaTypesEnum.text)
+                                        {
+                                            // Parse the fmtp attribute for audio/video announcements.
+                                            if (TrySplitAttributeValue(
+                                                l,
+                                                SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX.Length,
+                                                out var avFormatIDStart,
+                                                out var avFormatIDLength,
+                                                out var fmtpStart))
                                             {
-                                                activeAnnouncement.ApplicationMediaFormats[formatID] = activeAnnouncement.ApplicationMediaFormats[formatID].WithUpdatedRtpmap(rtpmap);
+                                                var avFormatID = l.Slice(avFormatIDStart, avFormatIDLength);
+                                                if (int.TryParse(avFormatID, out var fmtpFormatId))
+                                                {
+                                                    var fmtp = l.Slice(fmtpStart).ToString();
+                                                    if (activeAnnouncement.MediaFormats.ContainsKey(fmtpFormatId))
+                                                    {
+                                                        activeAnnouncement.MediaFormats[fmtpFormatId] = activeAnnouncement.MediaFormats[fmtpFormatId].WithUpdatedFmtp(fmtp);
+                                                    }
+                                                    else
+                                                    {
+                                                        // Store the fmtp attribute for use when the rtpmap attribute turns up.
+                                                        if (_pendingFmtp.ContainsKey(fmtpFormatId))
+                                                        {
+                                                            _pendingFmtp.Remove(fmtpFormatId);
+                                                        }
+                                                        _pendingFmtp.Add(fmtpFormatId, fmtp);
+                                                    }
+                                                }
+                                                else
+                                                {
+                                                    logger.LogWarning("Invalid media format parameter attribute in SDP: {sdpLine}", sdpLineTrimmedSpan.ToString());
+                                                }
                                             }
                                             else
                                             {
-                                                activeAnnouncement.ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID, rtpmap, null));
+                                                activeAnnouncement.AddExtra(sdpLineTrimmedSpan.ToString());
                                             }
                                         }
                                         else
                                         {
-                                            activeAnnouncement.AddExtra(sdpLineTrimmed);
-                                        }
-                                    }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("There was no active media announcement for a media format attribute, ignoring.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    if (activeAnnouncement.Media == SDPMediaTypesEnum.audio || activeAnnouncement.Media == SDPMediaTypesEnum.video || activeAnnouncement.Media == SDPMediaTypesEnum.text)
-                                    {
-                                        // Parse the fmtp attribute for audio/video announcements.
-                                        Match formatAttributeMatch = Regex.Match(sdpLineTrimmed, SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX + @"(?<id>\d+)\s+(?<attribute>.*)$");
-                                        if (formatAttributeMatch.Success)
-                                        {
-                                            string avFormatID = formatAttributeMatch.Result("${id}");
-                                            string fmtp = formatAttributeMatch.Result("${attribute}");
-
-                                            if (Int32.TryParse(avFormatID, out int id))
+                                            // Parse the fmtp attribute for NON audio/video announcements.
+                                            if (TrySplitAttributeValue(
+                                                l,
+                                                SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX.Length,
+                                                out var formatIDStart,
+                                                out var formatIDLength,
+                                                out var fmtpStart))
                                             {
-                                                if (activeAnnouncement.MediaFormats.ContainsKey(id))
+                                                var formatID = l.Slice(formatIDStart, formatIDLength).ToString();
+                                                var fmtp = l.Slice(fmtpStart).ToString();
+
+                                                if (activeAnnouncement.ApplicationMediaFormats.ContainsKey(formatID))
                                                 {
-                                                    activeAnnouncement.MediaFormats[id] = activeAnnouncement.MediaFormats[id].WithUpdatedFmtp(fmtp);
+                                                    activeAnnouncement.ApplicationMediaFormats[formatID] = activeAnnouncement.ApplicationMediaFormats[formatID].WithUpdatedFmtp(fmtp);
                                                 }
                                                 else
                                                 {
-                                                    // Store the fmtp attribute for use when the rtpmap attribute turns up.
-                                                    if (_pendingFmtp.ContainsKey(id))
-                                                    {
-                                                        _pendingFmtp.Remove(id);
-                                                    }
-                                                    _pendingFmtp.Add(id, fmtp);
+                                                    activeAnnouncement.ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID, null, fmtp));
                                                 }
                                             }
                                             else
                                             {
-                                                logger.LogWarning("Invalid media format parameter attribute in SDP: {sdpLine}", sdpLine);
+                                                activeAnnouncement.AddExtra(sdpLineTrimmedSpan.ToString());
                                             }
                                         }
-                                        else
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("There was no active media announcement for a media format parameter attribute, ignoring.");
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPSecurityDescription.CRYPTO_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    //2018-12-21 rj2: add a=crypto
+                                    if (activeAnnouncement != null)
+                                    {
+                                        try
+                                        {
+                                            activeAnnouncement.AddCryptoLine(sdpLineTrimmedSpan.ToString());
+                                        }
+                                        catch (FormatException fex)
                                         {
-                                            activeAnnouncement.AddExtra(sdpLineTrimmed);
+                                            logger.LogWarning("Error Parsing SDP-Line(a=crypto) {Exception}", fex);
                                         }
                                     }
+                                    break;
+
+                                case var _ when StartsWithAttribute(sdpLineTrimmedSpan, MEDIA_ID_ATTRIBUTE_PREFIX):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        activeAnnouncement.MediaID = SliceAfterColon(sdpLineTrimmedSpan).ToString();
+                                    }
                                     else
                                     {
-                                        // Parse the fmtp attribute for NON audio/video announcements.
-                                        Match formatAttributeMatch = Regex.Match(sdpLineTrimmed, SDPMediaAnnouncement.MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX + @"(?<id>\S+)\s+(?<attribute>.*)$");
-                                        if (formatAttributeMatch.Success)
+                                        logger.LogWarning("A media ID can only be set on a media announcement.");
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SSRC_GROUP_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        var fields = SliceAfterColon(sdpLineTrimmedSpan);
+                                        var fieldIndex = 0;
+
+                                        // Set the ID.
+                                        foreach (var fieldRange in fields.Split(' '))
                                         {
-                                            string formatID = formatAttributeMatch.Result("${id}");
-                                            string fmtp = formatAttributeMatch.Result("${attribute}");
+                                            var ssrcField = fields[fieldRange];
+                                            if (fieldIndex == 0)
+                                            {
+                                                activeAnnouncement.SsrcGroupID = ssrcField.ToString();
+                                            }
+                                            else if (uint.TryParse(ssrcField, out var ssrc))
+                                            {
+                                                // Add attributes for each of the SSRC values.
+                                                activeAnnouncement.SsrcAttributes.Add(new SDPSsrcAttribute(ssrc, null, activeAnnouncement.SsrcGroupID));
+                                            }
+
+                                            fieldIndex++;
+                                        }
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("A ssrc-group ID can only be set on a media announcement.");
+                                    }
+                                    break;
+
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        var ssrcFields = SliceAfterColon(sdpLineTrimmedSpan);
+                                        var ssrcField = default(ReadOnlySpan<char>);
+                                        var cnameField = default(ReadOnlySpan<char>);
+                                        var fieldIndex = 0;
 
-                                            if (activeAnnouncement.ApplicationMediaFormats.ContainsKey(formatID))
+                                        foreach (var fieldRange in ssrcFields.Split(' '))
+                                        {
+                                            if (fieldIndex == 0)
                                             {
-                                                activeAnnouncement.ApplicationMediaFormats[formatID] = activeAnnouncement.ApplicationMediaFormats[formatID].WithUpdatedFmtp(fmtp);
+                                                ssrcField = ssrcFields[fieldRange];
                                             }
-                                            else
+                                            else if (fieldIndex == 1)
                                             {
-                                                activeAnnouncement.ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID, null, fmtp));
+                                                cnameField = ssrcFields[fieldRange];
+                                                break;
                                             }
+
+                                            fieldIndex++;
                                         }
-                                        else
+
+                                        if (uint.TryParse(ssrcField, out var ssrc))
                                         {
-                                            activeAnnouncement.AddExtra(sdpLineTrimmed);
+                                            var ssrcAttribute = activeAnnouncement.SsrcAttributes.FirstOrDefault(x => x.SSRC == ssrc);
+                                            if (ssrcAttribute == null)
+                                            {
+                                                ssrcAttribute = new SDPSsrcAttribute(ssrc, null, null);
+                                                activeAnnouncement.SsrcAttributes.Add(ssrcAttribute);
+                                            }
+
+                                            if (!cnameField.IsEmpty &&
+                                                cnameField.StartsWith(SDPSsrcAttribute.MEDIA_CNAME_ATTRIBUE_PREFIX, StringComparison.Ordinal))
+                                            {
+                                                ssrcAttribute.Cname = cnameField.Slice(cnameField.IndexOf(':') + 1).ToString();
+                                            }
                                         }
                                     }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("There was no active media announcement for a media format parameter attribute, ignoring.");
-                                }
-                                break;
+                                    else
+                                    {
+                                        logger.LogWarning("An ssrc attribute can only be set on a media announcement.");
+                                    }
+                                    break;
 
-                            case var l when l.StartsWith(SDPSecurityDescription.CRYPTO_ATTRIBUE_PREFIX):
-                                //2018-12-21 rj2: add a=crypto
-                                if (activeAnnouncement != null)
-                                {
-                                    try
+                                case var _ when TryParseMediaStreamStatus(sdpLineTrimmedSpan, out var mediaStreamStatus):
+                                    if (activeAnnouncement != null)
                                     {
-                                        activeAnnouncement.AddCryptoLine(sdpLineTrimmed);
+                                        activeAnnouncement.MediaStreamStatus = mediaStreamStatus;
                                     }
-                                    catch (FormatException fex)
+                                    else
                                     {
-                                        logger.LogWarning("Error Parsing SDP-Line(a=crypto) {Exception}", fex);
+                                        sdp.SessionMediaStreamStatus = mediaStreamStatus;
                                     }
-                                }
-                                break;
+                                    break;
 
-                            case var x when x.StartsWith($"a={MEDIA_ID_ATTRIBUTE_PREFIX}"):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.MediaID = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A media ID can only be set on a media announcement.");
-                                }
-                                break;
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SCTP_MAP_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        var sctpMapFields = SliceAfterColon(sdpLineTrimmedSpan);
+                                        activeAnnouncement.SctpMap = sctpMapFields.ToString();
 
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SSRC_GROUP_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string[] fields = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1).Split(' ');
+                                        var sctpPortField = default(ReadOnlySpan<char>);
+                                        var maxMessageSizeField = default(ReadOnlySpan<char>);
+                                        var fieldIndex = 0;
 
-                                    // Set the ID.
-                                    if (fields.Length > 0)
+                                        foreach (var fieldRange in sctpMapFields.Split(' '))
+                                        {
+                                            if (fieldIndex == 0)
+                                            {
+                                                sctpPortField = sctpMapFields[fieldRange];
+                                            }
+                                            else if (fieldIndex == 2)
+                                            {
+                                                maxMessageSizeField = sctpMapFields[fieldRange];
+                                                break;
+                                            }
+
+                                            fieldIndex++;
+                                        }
+
+                                        if (ushort.TryParse(sctpPortField, out var sctpPort))
+                                        {
+                                            activeAnnouncement.SctpPort = sctpPort;
+                                        }
+                                        else
+                                        {
+                                            logger.LogWarning("An sctp-port value of {sctpPortStr} was not recognised as a valid port.", sctpPortField.ToString());
+                                        }
+
+                                        if (!long.TryParse(maxMessageSizeField, out activeAnnouncement.MaxMessageSize))
+                                        {
+                                            logger.LogWarning("A max-message-size value of {maxMessageSizeStr} was not recognised as a valid long.", maxMessageSizeField.ToString());
+                                        }
+                                    }
+                                    else
                                     {
-                                        activeAnnouncement.SsrcGroupID = fields[0];
+                                        logger.LogWarning("An sctpmap attribute can only be set on a media announcement.");
                                     }
+                                    break;
 
-                                    // Add attributes for each of the SSRC values.
-                                    for (int i = 1; i < fields.Length; i++)
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SCTP_PORT_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
                                     {
-                                        if (uint.TryParse(fields[i], out var ssrc))
+                                        var sctpPortStr = SliceAfterColon(sdpLineTrimmedSpan);
+
+                                        if (ushort.TryParse(sctpPortStr, out var sctpPort))
+                                        {
+                                            activeAnnouncement.SctpPort = sctpPort;
+                                        }
+                                        else
                                         {
-                                            activeAnnouncement.SsrcAttributes.Add(new SDPSsrcAttribute(ssrc, null, activeAnnouncement.SsrcGroupID));
+                                            logger.LogWarning("An sctp-port value of {sctpPortStr} was not recognised as a valid port.", sctpPortStr.ToString());
                                         }
                                     }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A ssrc-group ID can only be set on a media announcement.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string[] ssrcFields = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1).Split(' ');
+                                    else
+                                    {
+                                        logger.LogWarning("An sctp-port attribute can only be set on a media announcement.");
+                                    }
+                                    break;
 
-                                    if (ssrcFields.Length > 0 && uint.TryParse(ssrcFields[0], out var ssrc))
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_MAX_MESSAGE_SIZE_ATTRIBUE_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
                                     {
-                                        var ssrcAttribute = activeAnnouncement.SsrcAttributes.FirstOrDefault(x => x.SSRC == ssrc);
-                                        if (ssrcAttribute == null)
+                                        var maxMessageSizeStr = SliceAfterColon(sdpLineTrimmedSpan);
+                                        if (!long.TryParse(maxMessageSizeStr, out activeAnnouncement.MaxMessageSize))
                                         {
-                                            ssrcAttribute = new SDPSsrcAttribute(ssrc, null, null);
-                                            activeAnnouncement.SsrcAttributes.Add(ssrcAttribute);
+                                            logger.LogWarning("A max-message-size value of {maxMessageSizeStr} was not recognised as a valid long.", maxMessageSizeStr.ToString());
                                         }
+                                    }
+                                    else
+                                    {
+                                        logger.LogWarning("A max-message-size attribute can only be set on a media announcement.");
+                                    }
+                                    break;
 
-                                        if (ssrcFields.Length > 1)
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PATH_ACCEPT_TYPES_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        var acceptTypes = SliceAfterColon(sdpLineTrimmedSpan).Trim();
+                                        var acceptTypesList = new List<string>();
+                                        foreach (var acceptTypeRange in acceptTypes.Split(' '))
                                         {
-                                            if (ssrcFields[1].StartsWith(SDPSsrcAttribute.MEDIA_CNAME_ATTRIBUE_PREFIX))
-                                            {
-                                                ssrcAttribute.Cname = ssrcFields[1].Substring(ssrcFields[1].IndexOf(':') + 1);
-                                            }
+                                            acceptTypesList.Add(acceptTypes[acceptTypeRange].ToString());
                                         }
+                                        activeAnnouncement.MessageMediaFormat.AcceptTypes = acceptTypesList;
                                     }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("An ssrc attribute can only be set on a media announcement.");
-                                }
-                                break;
+                                    else
+                                    {
+                                        logger.LogWarning("A accept-types attribute can only be set on a media announcement.");
+                                    }
+                                    break;
 
-                            case var x when MediaStreamStatusType.IsMediaStreamStatusAttribute(x, out var mediaStreamStatus):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.MediaStreamStatus = mediaStreamStatus;
-                                }
-                                else
-                                {
-                                    sdp.SessionMediaStreamStatus = mediaStreamStatus;
-                                }
-                                break;
+                                case var _ when sdpLineTrimmedSpan.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PATH_MSRP_PREFIX, StringComparison.Ordinal):
+                                    if (activeAnnouncement != null)
+                                    {
+                                        var pathStr = SliceAfterColon(sdpLineTrimmedSpan);
+                                        var pathTrimmedStr = pathStr.Slice(pathStr.IndexOf(':') + 3);
+                                        activeAnnouncement.MessageMediaFormat.IP = pathTrimmedStr.Slice(0, pathTrimmedStr.IndexOf(':')).ToString();
 
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SCTP_MAP_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.SctpMap = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
+                                        pathTrimmedStr = pathTrimmedStr.Slice(pathTrimmedStr.IndexOf(':') + 1);
+                                        activeAnnouncement.MessageMediaFormat.Port = pathTrimmedStr.Slice(0, pathTrimmedStr.IndexOf('/')).ToString();
 
-                                    (var sctpPortStr, _, var maxMessageSizeStr) = activeAnnouncement.SctpMap.Split(' ');
+                                        pathTrimmedStr = pathTrimmedStr.Slice(pathTrimmedStr.IndexOf('/') + 1);
+                                        activeAnnouncement.MessageMediaFormat.Endpoint = pathTrimmedStr.ToString();
 
-                                    if (ushort.TryParse(sctpPortStr, out var sctpPort))
-                                    {
-                                        activeAnnouncement.SctpPort = sctpPort;
                                     }
                                     else
                                     {
-                                        logger.LogWarning("An sctp-port value of {sctpPortStr} was not recognised as a valid port.", sctpPortStr);
-                                    }
-
-                                    if (!long.TryParse(maxMessageSizeStr, out activeAnnouncement.MaxMessageSize))
-                                    {
-                                        logger.LogWarning("A max-message-size value of {maxMessageSizeStr} was not recognised as a valid long.", maxMessageSizeStr);
+                                        logger.LogWarning("A path attribute can only be set on a media announcement.");
                                     }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("An sctpmap attribute can only be set on a media announcement.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_SCTP_PORT_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string sctpPortStr = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
+                                    break;
 
-                                    if (ushort.TryParse(sctpPortStr, out var sctpPort))
+                                default:
+                                    if (activeAnnouncement != null)
                                     {
-                                        activeAnnouncement.SctpPort = sctpPort;
+                                        activeAnnouncement.AddExtra(sdpLineTrimmedSpan.ToString());
                                     }
                                     else
                                     {
-                                        logger.LogWarning("An sctp-port value of {sctpPortStr} was not recognised as a valid port.", sctpPortStr);
-                                    }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("An sctp-port attribute can only be set on a media announcement.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_MAX_MESSAGE_SIZE_ATTRIBUE_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string maxMessageSizeStr = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                    if (!long.TryParse(maxMessageSizeStr, out activeAnnouncement.MaxMessageSize))
-                                    {
-                                        logger.LogWarning("A max-message-size value of {maxMessageSizeStr} was not recognised as a valid long.", maxMessageSizeStr);
-                                    }
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A max-message-size attribute can only be set on a media announcement.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PATH_ACCEPT_TYPES_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string acceptTypesStr = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                    var acceptTypesList = acceptTypesStr.Trim().Split(' ').ToList();
-                                    activeAnnouncement.MessageMediaFormat.AcceptTypes = acceptTypesList;
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A accept-types attribute can only be set on a media announcement.");
-                                }
-                                break;
-
-                            case var l when l.StartsWith(SDPMediaAnnouncement.MEDIA_FORMAT_PATH_MSRP_PREFIX):
-                                if (activeAnnouncement != null)
-                                {
-                                    string pathStr = sdpLineTrimmed.Substring(sdpLineTrimmed.IndexOf(':') + 1);
-                                    string pathTrimmedStr = pathStr.Substring(pathStr.IndexOf(':') + 3);
-                                    activeAnnouncement.MessageMediaFormat.IP = pathTrimmedStr.Substring(0, pathTrimmedStr.IndexOf(':'));
-                                    
-                                    pathTrimmedStr = pathTrimmedStr.Substring(pathTrimmedStr.IndexOf(':') + 1);
-                                    activeAnnouncement.MessageMediaFormat.Port = pathTrimmedStr.Substring(0, pathTrimmedStr.IndexOf('/'));
-                                    
-                                    pathTrimmedStr = pathTrimmedStr.Substring(pathTrimmedStr.IndexOf('/') + 1);
-                                    activeAnnouncement.MessageMediaFormat.Endpoint = pathTrimmedStr;
-                                    
-                                }
-                                else
-                                {
-                                    logger.LogWarning("A path attribute can only be set on a media announcement.");
-                                }
-                                break;
-
-                            default:
-                                if (activeAnnouncement != null)
-                                {
-                                    activeAnnouncement.AddExtra(sdpLineTrimmed);
-                                }
-                                else
-                                {
-                                    sdp.AddExtra(sdpLineTrimmed);
-                                }
-                                break;
+                                        sdp.AddExtra(sdpLineTrimmedSpan.ToString());
+                                    }
+                                    break;
+                            }
                         }
                     }
+                    finally
+                    {
+                        ArrayPool<Range>.Shared.Return(sdpLineRangeBuffer);
+                    }
 
                     return sdp;
                 }
@@ -824,37 +1058,69 @@ public string RawString()
 
         public override string ToString()
         {
-            string sdp =
-                "v=" + SDP_PROTOCOL_VERSION + CRLF +
-                "o=" + Owner + CRLF +
-                "s=" + SessionName + CRLF +
-                ((Connection != null) ? Connection.ToString() : null);
+            var sdp = new StringBuilder();
+            sdp.Append("v=").Append(SDP_PROTOCOL_VERSION).Append(CRLF)
+                .Append("o=").Append(Owner).Append(CRLF)
+                .Append("s=").Append(SessionName).Append(CRLF);
+
+            if (Connection != null)
+            {
+                sdp.Append(Connection);
+            }
+
             foreach (string bandwidth in BandwidthAttributes)
             {
-                sdp += "b=" + bandwidth + CRLF;
+                sdp.Append("b=").Append(bandwidth).Append(CRLF);
+            }
+
+            sdp.Append("t=").Append(Timing).Append(CRLF);
+
+            if (!string.IsNullOrWhiteSpace(IceUfrag))
+            {
+                sdp.Append("a=").Append(ICE_UFRAG_ATTRIBUTE_PREFIX).Append(':').Append(IceUfrag).Append(CRLF);
+            }
+
+            if (!string.IsNullOrWhiteSpace(IcePwd))
+            {
+                sdp.Append("a=").Append(ICE_PWD_ATTRIBUTE_PREFIX).Append(':').Append(IcePwd).Append(CRLF);
+            }
+
+            if (IceRole != null)
+            {
+                sdp.Append("a=").Append(SDP.ICE_SETUP_ATTRIBUTE_PREFIX).Append(':').Append(IceRole).Append(CRLF);
             }
 
-            sdp += "t=" + Timing + CRLF;
+            if (!string.IsNullOrWhiteSpace(DtlsFingerprint))
+            {
+                sdp.Append("a=").Append(DTLS_FINGERPRINT_ATTRIBUTE_PREFIX).Append(':').Append(DtlsFingerprint).Append(CRLF);
+            }
 
-            sdp += !string.IsNullOrWhiteSpace(IceUfrag) ? "a=" + ICE_UFRAG_ATTRIBUTE_PREFIX + ":" + IceUfrag + CRLF : null;
-            sdp += !string.IsNullOrWhiteSpace(IcePwd) ? "a=" + ICE_PWD_ATTRIBUTE_PREFIX + ":" + IcePwd + CRLF : null;
-            sdp += IceRole != null ? $"a={SDP.ICE_SETUP_ATTRIBUTE_PREFIX}:{IceRole}{CRLF}" : null;
-            sdp += !string.IsNullOrWhiteSpace(DtlsFingerprint) ? "a=" + DTLS_FINGERPRINT_ATTRIBUTE_PREFIX + ":" + DtlsFingerprint + CRLF : null;
             if (IceCandidates?.Count > 0)
             {
                 foreach (var candidate in IceCandidates)
                 {
-                    sdp += $"a={SDP.ICE_CANDIDATE_ATTRIBUTE_PREFIX}:{candidate}{CRLF}";
+                    sdp.Append("a=").Append(SDP.ICE_CANDIDATE_ATTRIBUTE_PREFIX).Append(':').Append(candidate).Append(CRLF);
                 }
             }
-            sdp += string.IsNullOrWhiteSpace(SessionDescription) ? null : "i=" + SessionDescription + CRLF;
-            sdp += string.IsNullOrWhiteSpace(URI) ? null : "u=" + URI + CRLF;
+
+            if (!string.IsNullOrWhiteSpace(SessionDescription))
+            {
+                sdp.Append("i=").Append(SessionDescription).Append(CRLF);
+            }
+
+            if (!string.IsNullOrWhiteSpace(URI))
+            {
+                sdp.Append("u=").Append(URI).Append(CRLF);
+            }
 
             if (OriginatorEmailAddresses != null && OriginatorEmailAddresses.Length > 0)
             {
                 foreach (string originatorAddress in OriginatorEmailAddresses)
                 {
-                    sdp += string.IsNullOrWhiteSpace(originatorAddress) ? null : "e=" + originatorAddress + CRLF;
+                    if (!string.IsNullOrWhiteSpace(originatorAddress))
+                    {
+                        sdp.Append("e=").Append(originatorAddress).Append(CRLF);
+                    }
                 }
             }
 
@@ -862,29 +1128,41 @@ public override string ToString()
             {
                 foreach (string originatorNumber in OriginatorPhoneNumbers)
                 {
-                    sdp += string.IsNullOrWhiteSpace(originatorNumber) ? null : "p=" + originatorNumber + CRLF;
+                    if (!string.IsNullOrWhiteSpace(originatorNumber))
+                    {
+                        sdp.Append("p=").Append(originatorNumber).Append(CRLF);
+                    }
                 }
             }
 
-            sdp += (Group == null) ? null : $"a={GROUP_ATRIBUTE_PREFIX}:{Group}" + CRLF;
+            if (Group != null)
+            {
+                sdp.Append("a=").Append(GROUP_ATRIBUTE_PREFIX).Append(':').Append(Group).Append(CRLF);
+            }
 
             foreach (string extra in ExtraSessionAttributes)
             {
-                sdp += string.IsNullOrWhiteSpace(extra) ? null : extra + CRLF;
+                if (!string.IsNullOrWhiteSpace(extra))
+                {
+                    sdp.Append(extra).Append(CRLF);
+                }
             }
 
             if (SessionMediaStreamStatus != null)
             {
-                sdp += MediaStreamStatusType.GetAttributeForMediaStreamStatus(SessionMediaStreamStatus.Value) + CRLF;
+                sdp.Append(MediaStreamStatusType.GetAttributeForMediaStreamStatus(SessionMediaStreamStatus.Value)).Append(CRLF);
             }
 
             //foreach (SDPMediaAnnouncement media in Media.OrderBy(x => x.MLineIndex).ThenBy(x => x.MediaID))
             foreach (SDPMediaAnnouncement media in Media.OrderBy(x => x.MLineIndex).ThenBy(x => x.MediaID))
             {
-                sdp += (media == null) ? null : media.ToString();
+                if (media != null)
+                {
+                    sdp.Append(media);
+                }
             }
 
-            return sdp;
+            return sdp.ToString();
         }
 
         /// <summary>
@@ -901,7 +1179,7 @@ public IPEndPoint GetSDPRTPEndPoint()
             {
                 return new IPEndPoint(IPAddress.Parse(sessionConnection.ConnectionAddress), firstMediaOffer.Port);
             }
-            else if(firstMediaOffer != null && firstMediaOffer.Connection != null)
+            else if (firstMediaOffer != null && firstMediaOffer.Connection != null)
             {
                 return new IPEndPoint(IPAddress.Parse(firstMediaOffer.Connection.ConnectionAddress), firstMediaOffer.Port);
             }
diff --git a/src/SIPSorcery/net/SDP/SDPAudioVideoMediaFormat.cs b/src/SIPSorcery/net/SDP/SDPAudioVideoMediaFormat.cs
index 6ba8342c9..1e0da6761 100644
--- a/src/SIPSorcery/net/SDP/SDPAudioVideoMediaFormat.cs
+++ b/src/SIPSorcery/net/SDP/SDPAudioVideoMediaFormat.cs
@@ -17,6 +17,8 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Polyfills;
+using SIPSorcery.Sys;
 using SIPSorceryMedia.Abstractions;
 
 namespace SIPSorcery.Net
@@ -148,7 +150,7 @@ public bool IsH264
         {
             get
             {
-                return (Rtpmap ?? "").ToUpperInvariant().Trim().StartsWith("H264");
+                return Rtpmap.AsSpan().Trim().StartsWith("H264", StringComparison.OrdinalIgnoreCase);
             }
         }
 
@@ -164,7 +166,7 @@ public bool IsMJPEG
         {
             get
             {
-                return (Rtpmap ?? "").ToUpperInvariant().Trim().StartsWith("JPEG");
+                return Rtpmap.AsSpan().Trim().StartsWith("JPEG", StringComparison.OrdinalIgnoreCase);
             }
         }
 
@@ -172,7 +174,7 @@ public bool isH265
         {
             get
             {
-                return (Rtpmap ?? "").ToUpperInvariant().Trim().StartsWith("H265");
+                return Rtpmap.AsSpan().Trim().StartsWith("H265", StringComparison.OrdinalIgnoreCase);
             }
         }
 
@@ -194,18 +196,20 @@ public bool CheckCompatible()
 
         private static Dictionary<string, string> ParseWebRtcParameters(string input)
         {
-            var parameters = new Dictionary<string, string>();
+            var parameters = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
             if (string.IsNullOrEmpty(input))
             {
                 return parameters;
             }
 
-            foreach (var pair in input.Split(';'))
+            Span<Range> keyValueRange = stackalloc Range[3];
+            var inputSpan = input.AsSpan();
+            foreach (var pairRange in inputSpan.Split(';'))
             {
-                var keyValue = pair.Split('=');
-                if (keyValue.Length == 2)
+                var pair = inputSpan[pairRange];
+                if (pair.Split(keyValueRange, '=') == 2)
                 {
-                    parameters[keyValue[0].Trim().ToLowerInvariant()] = keyValue[1].Trim();
+                    parameters[pair[keyValueRange[0]].Trim().ToString()] = pair[keyValueRange[1]].Trim().ToString();
                 }
             }
 
@@ -314,7 +318,7 @@ public SDPAudioVideoMediaFormat(TextFormat textFormat)
         {
             Kind = SDPMediaTypesEnum.text;
             ID = textFormat.FormatID;
-            Rtpmap = null;  
+            Rtpmap = null;
             Fmtp = textFormat.Parameters;
             _isEmpty = false;
 
@@ -458,7 +462,7 @@ public static bool AreMatch(SDPAudioVideoMediaFormat format1, SDPAudioVideoMedia
             // rtpmap takes priority as well known format ID's can be overruled.
             if (format1.Rtpmap != null && format2.Rtpmap != null)
             {
-                if (string.Equals(format1.Rtpmap.Trim(), format2.Rtpmap.Trim(), StringComparison.OrdinalIgnoreCase))
+                if (format1.Rtpmap.AsSpan().Trim().Equals(format2.Rtpmap.AsSpan().Trim(), StringComparison.OrdinalIgnoreCase))
                 {
                     return true;
                 }
@@ -471,7 +475,7 @@ public static bool AreMatch(SDPAudioVideoMediaFormat format1, SDPAudioVideoMedia
                 return true;
             }
             return false;
-            
+
         }
 
         /// <summary>
@@ -558,24 +562,46 @@ public static bool TryParseRtpmap(string rtpmap, out string name, out int clockR
             }
             else
             {
-                string[] fields = rtpmap.Trim().Split('/');
+                var rtpmapSpan = rtpmap.AsSpan().Trim();
+                var nameSpan = default(ReadOnlySpan<char>);
+                var clockRateSpan = default(ReadOnlySpan<char>);
+                var channelsSpan = default(ReadOnlySpan<char>);
+                var fieldIndex = 0;
+
+                foreach (var fieldRange in rtpmapSpan.Split('/'))
+                {
+                    var field = rtpmapSpan[fieldRange].Trim();
+
+                    if (fieldIndex == 0)
+                    {
+                        nameSpan = field;
+                    }
+                    else if (fieldIndex == 1)
+                    {
+                        clockRateSpan = field;
+                    }
+                    else if (fieldIndex == 2)
+                    {
+                        channelsSpan = field;
+                        break;
+                    }
+
+                    fieldIndex++;
+                }
 
-                if (fields.Length >= 2)
+                if (fieldIndex >= 1)
                 {
-                    name = fields[0].Trim();
-                    if (!int.TryParse(fields[1].Trim(), out clockRate))
+                    if (!int.TryParse(clockRateSpan, out clockRate))
                     {
                         return false;
                     }
 
-                    if (fields.Length >= 3)
+                    if (!channelsSpan.IsEmpty && !int.TryParse(channelsSpan, out channels))
                     {
-                        if (!int.TryParse(fields[2].Trim(), out channels))
-                        {
-                            return false;
-                        }
+                        return false;
                     }
 
+                    name = nameSpan.ToString();
                     return true;
                 }
                 else
@@ -630,8 +656,8 @@ public static SDPAudioVideoMediaFormat GetFormatForName(List<SDPAudioVideoMediaF
             }
             else
             {
-                return formats.Any(x => x.Name()?.ToLower() == formatName?.ToLower()) ?
-                   formats.First(x => x.Name()?.ToLower() == formatName?.ToLower()) :
+                return formats.Any(x => string.Equals(x.Name(), formatName, StringComparison.OrdinalIgnoreCase)) ?
+                   formats.First(x => string.Equals(x.Name(), formatName, StringComparison.OrdinalIgnoreCase)) :
                    Empty;
             }
         }
diff --git a/src/SIPSorcery/net/SDP/SDPConnectionInformation.cs b/src/SIPSorcery/net/SDP/SDPConnectionInformation.cs
index b3f12d789..4f64aafe2 100644
--- a/src/SIPSorcery/net/SDP/SDPConnectionInformation.cs
+++ b/src/SIPSorcery/net/SDP/SDPConnectionInformation.cs
@@ -13,8 +13,11 @@
 // BSD 3-Clause "New" or "Revised" License, see included LICENSE.md file.
 //-----------------------------------------------------------------------------
 
+using System;
 using System.Net;
 using System.Net.Sockets;
+using Polyfills;
+using SIPSorcery.Sys;
 
 namespace SIPSorcery.Net
 {
@@ -52,16 +55,34 @@ public SDPConnectionInformation(IPAddress connectionAddress)
         public static SDPConnectionInformation ParseConnectionInformation(string connectionLine)
         {
             SDPConnectionInformation connectionInfo = new SDPConnectionInformation();
-            string[] connectionFields = connectionLine.Substring(2).Trim().Split(' ');
-            connectionInfo.ConnectionNetworkType = connectionFields[0].Trim();
-            connectionInfo.ConnectionAddressType = connectionFields[1].Trim();
-            connectionInfo.ConnectionAddress = connectionFields[2].Trim();
+            var connectionFields = connectionLine.AsSpan(2).Trim();
+            var fieldIndex = 0;
+            foreach (var fieldRange in connectionFields.Split(' '))
+            {
+                var field = connectionFields[fieldRange].Trim().ToString();
+                if (fieldIndex == 0)
+                {
+                    connectionInfo.ConnectionNetworkType = field;
+                }
+                else if (fieldIndex == 1)
+                {
+                    connectionInfo.ConnectionAddressType = field;
+                }
+                else if (fieldIndex == 2)
+                {
+                    connectionInfo.ConnectionAddress = field;
+                    break;
+                }
+
+                fieldIndex++;
+            }
+
             return connectionInfo;
         }
 
         public override string ToString()
         {
-            return "c=" + ConnectionNetworkType + " " + ConnectionAddressType + " " + ConnectionAddress + m_CRLF;
+            return $"c={ConnectionNetworkType} {ConnectionAddressType} {ConnectionAddress}{m_CRLF}";
         }
     }
 }
diff --git a/src/SIPSorcery/net/SDP/SDPMediaAnnouncement.cs b/src/SIPSorcery/net/SDP/SDPMediaAnnouncement.cs
index c2ea65539..1f536cd9d 100644
--- a/src/SIPSorcery/net/SDP/SDPMediaAnnouncement.cs
+++ b/src/SIPSorcery/net/SDP/SDPMediaAnnouncement.cs
@@ -30,8 +30,9 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using System.Text.RegularExpressions;
 using Microsoft.Extensions.Logging;
+using Polyfills;
+using SIPSorcery.Sys;
 using SIPSorceryMedia.Abstractions;
 
 namespace SIPSorcery.Net
@@ -238,41 +239,42 @@ public SDPMediaAnnouncement(SDPMediaTypesEnum mediaType, SDPConnectionInformatio
             Port = port;
             Connection = connection;
 
-            MessageMediaFormat =  messageMediaFormat;
+            MessageMediaFormat = messageMediaFormat;
         }
 
         public void ParseMediaFormats(string formatList)
         {
             if (!String.IsNullOrWhiteSpace(formatList))
             {
-                string[] formatIDs = Regex.Split(formatList, @"\s");
-                if (formatIDs != null)
+                var formatListSpan = formatList.AsSpan();
+                foreach (var formatIDRange in formatListSpan.SplitAny())
                 {
-                    foreach (string formatID in formatIDs)
+                    var formatIDSpan = formatListSpan[formatIDRange];
+
+                    if (Media == SDPMediaTypesEnum.application)
                     {
-                        if (Media == SDPMediaTypesEnum.application)
-                        {
-                            ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID));
-                        }
-                        else if (Media == SDPMediaTypesEnum.message)
-                        {
-                            //TODO
-                        }
-                        else
+                        var formatID = formatIDSpan.ToString();
+                        ApplicationMediaFormats.Add(formatID, new SDPApplicationMediaFormat(formatID));
+                    }
+                    else if (Media == SDPMediaTypesEnum.message)
+                    {
+                        //TODO
+                    }
+                    else
+                    {
+                        if (int.TryParse(formatIDSpan, out var id)
+                            && !MediaFormats.ContainsKey(id)
+                            && id < SDPAudioVideoMediaFormat.DYNAMIC_ID_MIN)
                         {
-                            if (Int32.TryParse(formatID, out int id)
-                                && !MediaFormats.ContainsKey(id)
-                                && id < SDPAudioVideoMediaFormat.DYNAMIC_ID_MIN)
+                            var formatID = formatIDSpan.ToString();
+                            if (Enum.IsDefined(typeof(SDPWellKnownMediaFormatsEnum), id) &&
+                                Enum.TryParse<SDPWellKnownMediaFormatsEnum>(formatID, out var wellKnown))
+                            {
+                                MediaFormats.Add(id, new SDPAudioVideoMediaFormat(wellKnown));
+                            }
+                            else
                             {
-                                if (Enum.IsDefined(typeof(SDPWellKnownMediaFormatsEnum), id) &&
-                                    Enum.TryParse<SDPWellKnownMediaFormatsEnum>(formatID, out var wellKnown))
-                                {
-                                    MediaFormats.Add(id, new SDPAudioVideoMediaFormat(wellKnown));
-                                }
-                                else
-                                {
-                                    logger.LogWarning("Excluding unrecognised well known media format ID {FormatID}.", id);
-                                }
+                                logger.LogWarning("Excluding unrecognised well known media format ID {FormatID}.", id);
                             }
                         }
                     }
@@ -282,73 +284,107 @@ public void ParseMediaFormats(string formatList)
 
         public override string ToString()
         {
-            string announcement = "m=" + Media + " " + Port + " " + Transport + " " + GetFormatListToString() + m_CRLF;
+            var announcement = new StringBuilder();
+            announcement.Append("m=").Append(Media).Append(' ').Append(Port).Append(' ').Append(Transport).Append(' ')
+                .Append(GetFormatListToString()).Append(m_CRLF);
 
-            announcement += !string.IsNullOrWhiteSpace(MediaDescription) ? "i=" + MediaDescription + m_CRLF : null;
+            if (!string.IsNullOrWhiteSpace(MediaDescription))
+            {
+                announcement.Append("i=").Append(MediaDescription).Append(m_CRLF);
+            }
 
-            announcement += (Connection == null) ? null : Connection.ToString();
+            if (Connection != null)
+            {
+                announcement.Append(Connection);
+            }
 
             if (TIASBandwidth > 0)
             {
-                announcement += TIAS_BANDWIDTH_ATTRIBUE_PREFIX + TIASBandwidth + m_CRLF;
+                announcement.Append(TIAS_BANDWIDTH_ATTRIBUE_PREFIX).Append(TIASBandwidth).Append(m_CRLF);
             }
 
             foreach (string bandwidthAttribute in BandwidthAttributes)
             {
-                announcement += "b=" + bandwidthAttribute + m_CRLF;
+                announcement.Append("b=").Append(bandwidthAttribute).Append(m_CRLF);
+            }
+
+            if (!string.IsNullOrWhiteSpace(IceUfrag))
+            {
+                announcement.Append("a=").Append(SDP.ICE_UFRAG_ATTRIBUTE_PREFIX).Append(':').Append(IceUfrag).Append(m_CRLF);
             }
 
-            announcement += !string.IsNullOrWhiteSpace(IceUfrag) ? "a=" + SDP.ICE_UFRAG_ATTRIBUTE_PREFIX + ":" + IceUfrag + m_CRLF : null;
-            announcement += !string.IsNullOrWhiteSpace(IcePwd) ? "a=" + SDP.ICE_PWD_ATTRIBUTE_PREFIX + ":" + IcePwd + m_CRLF : null;
-            announcement += !string.IsNullOrWhiteSpace(DtlsFingerprint) ? "a=" + SDP.DTLS_FINGERPRINT_ATTRIBUTE_PREFIX + ":" + DtlsFingerprint + m_CRLF : null;
-            announcement += IceRole != null ? $"a={SDP.ICE_SETUP_ATTRIBUTE_PREFIX}:{IceRole}{m_CRLF}" : null; 
+            if (!string.IsNullOrWhiteSpace(IcePwd))
+            {
+                announcement.Append("a=").Append(SDP.ICE_PWD_ATTRIBUTE_PREFIX).Append(':').Append(IcePwd).Append(m_CRLF);
+            }
+
+            if (!string.IsNullOrWhiteSpace(DtlsFingerprint))
+            {
+                announcement.Append("a=").Append(SDP.DTLS_FINGERPRINT_ATTRIBUTE_PREFIX).Append(':').Append(DtlsFingerprint).Append(m_CRLF);
+            }
+
+            if (IceRole != null)
+            {
+                announcement.Append("a=").Append(SDP.ICE_SETUP_ATTRIBUTE_PREFIX).Append(':').Append(IceRole).Append(m_CRLF);
+            }
 
             if (IceCandidates?.Count() > 0)
             {
                 foreach (var candidate in IceCandidates)
                 {
-                    announcement += $"a={SDP.ICE_CANDIDATE_ATTRIBUTE_PREFIX}:{candidate}{m_CRLF}";
+                    announcement.Append("a=").Append(SDP.ICE_CANDIDATE_ATTRIBUTE_PREFIX).Append(':').Append(candidate).Append(m_CRLF);
                 }
             }
 
             if (IceOptions != null)
             {
-                announcement += $"a={SDP.ICE_OPTIONS}:" + IceOptions + m_CRLF;
+                announcement.Append("a=").Append(SDP.ICE_OPTIONS).Append(':').Append(IceOptions).Append(m_CRLF);
             }
 
             if (IceEndOfCandidates)
             {
-                announcement += $"a={SDP.END_ICE_CANDIDATES_ATTRIBUTE}" + m_CRLF;
+                announcement.Append("a=").Append(SDP.END_ICE_CANDIDATES_ATTRIBUTE).Append(m_CRLF);
+            }
+
+            if (!string.IsNullOrWhiteSpace(MediaID))
+            {
+                announcement.Append("a=").Append(SDP.MEDIA_ID_ATTRIBUTE_PREFIX).Append(':').Append(MediaID).Append(m_CRLF);
             }
 
-            announcement += !string.IsNullOrWhiteSpace(MediaID) ? "a=" + SDP.MEDIA_ID_ATTRIBUTE_PREFIX + ":" + MediaID + m_CRLF : null;
+            announcement.Append(GetFormatListAttributesToString());
 
-            announcement += GetFormatListAttributesToString();
+            foreach (var headerExtension in HeaderExtensions)
+            {
+                announcement.Append(MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX).Append(headerExtension.Value.Id).Append(' ')
+                    .Append(headerExtension.Value.Uri).Append(m_CRLF);
+            }
 
-            announcement += string.Join("", HeaderExtensions.Select(x => $"{MEDIA_EXTENSION_MAP_ATTRIBUE_PREFIX}{x.Value.Id} {x.Value.Uri}{m_CRLF}"));
             foreach (string extra in ExtraMediaAttributes)
             {
-                announcement += string.IsNullOrWhiteSpace(extra) ? null : extra + m_CRLF;
+                if (!string.IsNullOrWhiteSpace(extra))
+                {
+                    announcement.Append(extra).Append(m_CRLF);
+                }
             }
 
             foreach (SDPSecurityDescription desc in this.SecurityDescriptions)
             {
-                announcement += desc.ToString() + m_CRLF;
+                announcement.Append(desc.ToString()).Append(m_CRLF);
             }
 
             if (MediaStreamStatus != null)
             {
-                announcement += MediaStreamStatusType.GetAttributeForMediaStreamStatus(MediaStreamStatus.Value) + m_CRLF;
+                announcement.Append(MediaStreamStatusType.GetAttributeForMediaStreamStatus(MediaStreamStatus.Value)).Append(m_CRLF);
             }
 
             if (SsrcGroupID != null && SsrcAttributes.Count > 0)
             {
-                announcement += MEDIA_FORMAT_SSRC_GROUP_ATTRIBUE_PREFIX + SsrcGroupID;
+                announcement.Append(MEDIA_FORMAT_SSRC_GROUP_ATTRIBUE_PREFIX).Append(SsrcGroupID);
                 foreach (var ssrcAttr in SsrcAttributes)
                 {
-                    announcement += $" {ssrcAttr.SSRC}";
+                    announcement.Append(' ').Append(ssrcAttr.SSRC);
                 }
-                announcement += m_CRLF;
+                announcement.Append(m_CRLF);
             }
 
             if (SsrcAttributes.Count > 0)
@@ -357,11 +393,12 @@ public override string ToString()
                 {
                     if (!string.IsNullOrWhiteSpace(ssrcAttr.Cname))
                     {
-                        announcement += $"{MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX}{ssrcAttr.SSRC} {SDPSsrcAttribute.MEDIA_CNAME_ATTRIBUE_PREFIX}:{ssrcAttr.Cname}" + m_CRLF;
+                        announcement.Append(MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX).Append(ssrcAttr.SSRC).Append(' ')
+                            .Append(SDPSsrcAttribute.MEDIA_CNAME_ATTRIBUE_PREFIX).Append(':').Append(ssrcAttr.Cname).Append(m_CRLF);
                     }
                     else
                     {
-                        announcement += $"{MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX}{ssrcAttr.SSRC}" + m_CRLF;
+                        announcement.Append(MEDIA_FORMAT_SSRC_ATTRIBUE_PREFIX).Append(ssrcAttr.SSRC).Append(m_CRLF);
                     }
                 }
             }
@@ -371,22 +408,22 @@ public override string ToString()
             // an application sets it then it's likely to be for a specific reason.
             if (SctpMap != null)
             {
-                announcement += $"{MEDIA_FORMAT_SCTP_MAP_ATTRIBUE_PREFIX}{SctpMap}" + m_CRLF;
+                announcement.Append(MEDIA_FORMAT_SCTP_MAP_ATTRIBUE_PREFIX).Append(SctpMap).Append(m_CRLF);
             }
             else
             {
                 if (SctpPort != null)
                 {
-                    announcement += $"{MEDIA_FORMAT_SCTP_PORT_ATTRIBUE_PREFIX}{SctpPort}" + m_CRLF;
+                    announcement.Append(MEDIA_FORMAT_SCTP_PORT_ATTRIBUE_PREFIX).Append(SctpPort).Append(m_CRLF);
                 }
 
                 if (MaxMessageSize != 0)
                 {
-                    announcement += $"{MEDIA_FORMAT_MAX_MESSAGE_SIZE_ATTRIBUE_PREFIX}{MaxMessageSize}" + m_CRLF;
+                    announcement.Append(MEDIA_FORMAT_MAX_MESSAGE_SIZE_ATTRIBUE_PREFIX).Append(MaxMessageSize).Append(m_CRLF);
                 }
             }
 
-            return announcement;
+            return announcement.ToString();
         }
 
         public string GetFormatListToString()
@@ -408,13 +445,20 @@ public string GetFormatListToString()
             }
             else
             {
-                string mediaFormatList = null;
+                var mediaFormatList = default(StringBuilder);
                 foreach (var mediaFormat in MediaFormats)
                 {
-                    mediaFormatList += mediaFormat.Key + " ";
+                    mediaFormatList ??= new StringBuilder();
+                    mediaFormatList.Append(mediaFormat.Key).Append(' ');
                 }
 
-                return (mediaFormatList != null) ? mediaFormatList.Trim() : null;
+                if (mediaFormatList == null)
+                {
+                    return null;
+                }
+
+                mediaFormatList.Length--;
+                return mediaFormatList.ToString();
             }
         }
 
@@ -429,12 +473,14 @@ public string GetFormatListAttributesToString()
                     {
                         if (appFormat.Value.Rtpmap != null)
                         {
-                            sb.Append($"{MEDIA_FORMAT_ATTRIBUTE_PREFIX}{appFormat.Key} {appFormat.Value.Rtpmap}{m_CRLF}");
+                            sb.Append(MEDIA_FORMAT_ATTRIBUTE_PREFIX).Append(appFormat.Key).Append(' ')
+                                .Append(appFormat.Value.Rtpmap).Append(m_CRLF);
                         }
 
                         if (appFormat.Value.Fmtp != null)
                         {
-                            sb.Append($"{MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX}{appFormat.Key} {appFormat.Value.Fmtp}{m_CRLF}");
+                            sb.Append(MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX).Append(appFormat.Key).Append(' ')
+                                .Append(appFormat.Value.Fmtp).Append(m_CRLF);
                         }
                     }
 
@@ -451,41 +497,45 @@ public string GetFormatListAttributesToString()
 
                 var mediaFormat = MessageMediaFormat;
                 var acceptTypes = mediaFormat.AcceptTypes;
-                if (acceptTypes != null && acceptTypes.Count >0)
+                if (acceptTypes != null && acceptTypes.Count > 0)
                 {
                     sb.Append(MEDIA_FORMAT_PATH_ACCEPT_TYPES_PREFIX);
                     foreach (var type in acceptTypes)
                     {
-                        sb.Append($"{type} ");
+                        sb.Append(type).Append(' ');
                     }
 
-                    sb.Append($"{m_CRLF}");
+                    sb.Append(m_CRLF);
                 }
 
-                if (mediaFormat.Endpoint != null )
+                if (mediaFormat.Endpoint != null)
                 {
-                    sb.Append($"{MEDIA_FORMAT_PATH_MSRP_PREFIX}//{Connection.ConnectionAddress}:{Port}/{mediaFormat.Endpoint}{m_CRLF}");
+                    sb.Append(MEDIA_FORMAT_PATH_MSRP_PREFIX).Append("//").Append(Connection.ConnectionAddress).Append(':')
+                        .Append(Port).Append('/').Append(mediaFormat.Endpoint).Append(m_CRLF);
                 }
-                
+
                 return sb.ToString();
             }
             else
             {
-                string formatAttributes = null;
+                var formatAttributes = default(StringBuilder);
 
                 if (MediaFormats != null)
                 {
                     foreach (var mediaFormat in MediaFormats.Select(y => y.Value))
                     {
+                        formatAttributes ??= new StringBuilder();
                         if (mediaFormat.Rtpmap == null)
                         {
                             // Well known media formats are not required to add an rtpmap but we do so any way as some SIP
                             // stacks don't work without it.
-                            formatAttributes += MEDIA_FORMAT_ATTRIBUTE_PREFIX + mediaFormat.ID + " " + mediaFormat.Name() + "/" + mediaFormat.ClockRate() + m_CRLF;
+                            formatAttributes.Append(MEDIA_FORMAT_ATTRIBUTE_PREFIX).Append(mediaFormat.ID).Append(' ')
+                                .Append(mediaFormat.Name()).Append('/').Append(mediaFormat.ClockRate()).Append(m_CRLF);
                         }
                         else
                         {
-                            formatAttributes += MEDIA_FORMAT_ATTRIBUTE_PREFIX + mediaFormat.ID + " " + mediaFormat.Rtpmap + m_CRLF;
+                            formatAttributes.Append(MEDIA_FORMAT_ATTRIBUTE_PREFIX).Append(mediaFormat.ID).Append(' ')
+                                .Append(mediaFormat.Rtpmap).Append(m_CRLF);
                         }
 
                         // Leaving out the feedback attribute for now. It should only be added where it's present in a parsed SDP packet or
@@ -495,18 +545,20 @@ public string GetFormatListAttributesToString()
                         {
                             foreach (var rtcpFeedbackMessage in mediaFormat.SupportedRtcpFeedbackMessages)
                             {
-                                formatAttributes += MEDIA_FORMAT_FEEDBACK_PREFIX + mediaFormat.ID + " " + rtcpFeedbackMessage + m_CRLF;
+                                formatAttributes.Append(MEDIA_FORMAT_FEEDBACK_PREFIX).Append(mediaFormat.ID).Append(' ')
+                                    .Append(rtcpFeedbackMessage).Append(m_CRLF);
                             }
                         }
 
                         if (mediaFormat.Fmtp != null)
                         {
-                            formatAttributes += MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX + mediaFormat.ID + " " + mediaFormat.Fmtp + m_CRLF;
+                            formatAttributes.Append(MEDIA_FORMAT_PARAMETERS_ATTRIBUE_PREFIX).Append(mediaFormat.ID).Append(' ')
+                                .Append(mediaFormat.Fmtp).Append(m_CRLF);
                         }
                     }
                 }
 
-                return formatAttributes;
+                return formatAttributes?.ToString();
             }
         }
 
diff --git a/src/SIPSorcery/net/SDP/SDPSecurityDescription.cs b/src/SIPSorcery/net/SDP/SDPSecurityDescription.cs
index 4b8a71603..03a38552d 100644
--- a/src/SIPSorcery/net/SDP/SDPSecurityDescription.cs
+++ b/src/SIPSorcery/net/SDP/SDPSecurityDescription.cs
@@ -10,6 +10,8 @@
 using System;
 using System.Collections.Generic;
 using System.Text;
+using Polyfills;
+using SIPSorcery.Sys;
 
 namespace SIPSorcery.Net
 {
@@ -177,7 +179,7 @@ public string LifeTimeString
                 }
                 set
                 {
-                    if (!TryParseLifeTimeString(value, out ulong lifeTime))
+                    if (!TryParseLifeTimeString(value, out var lifeTime))
                     {
                         throw new ArgumentException("LifeTimeString must be in format '2^n' where n is a positive integer", "LifeTimeString");
                     }
@@ -229,22 +231,23 @@ public KeyParameter(byte[] key, byte[] salt)
 
             public override string ToString()
             {
-                string s = KEY_METHOD + COLON + this.KeySaltBase64;
+                var s = new StringBuilder();
+                s.Append(KEY_METHOD).Append(COLON).Append(this.KeySaltBase64);
                 if (!string.IsNullOrWhiteSpace(this.LifeTimeString))
                 {
-                    s += PIPE + this.LifeTimeString;
+                    s.Append(PIPE).Append(this.LifeTimeString);
                 }
                 else if (this.LifeTime > 0)
                 {
-                    s += PIPE + this.LifeTime;
+                    s.Append(PIPE).Append(this.LifeTime);
                 }
 
                 if (this.MkiLength > 0 && this.MkiValue > 0)
                 {
-                    s += PIPE + this.MkiValue + COLON + this.MkiLength;
+                    s.Append(PIPE).Append(this.MkiValue).Append(COLON).Append(this.MkiLength);
                 }
 
-                return s;
+                return s.ToString();
             }
 
             public static KeyParameter Parse(string keyParamString, CryptoSuites cryptoSuite = CryptoSuites.AES_CM_128_HMAC_SHA1_80)
@@ -260,20 +263,87 @@ public static bool TryParse(string keyParamString, out KeyParameter keyParam, Cr
             {
                 keyParam = null;
 
+                static bool CheckValidKeyInfoCharacters(ReadOnlySpan<char> keyInfo)
+                {
+                    foreach (var c in keyInfo)
+                    {
+                        if (c < 0x21 || c > 0x7e)
+                        {
+                            return false;
+                        }
+                    }
+                    return true;
+                }
+
+                static bool ParseKeyInfo(ReadOnlySpan<char> keyInfo, out string mkiValue, out string mkiLen, out string lifeTimeString, out string base64KeySalt)
+                {
+                    mkiValue = null;
+                    mkiLen = null;
+                    lifeTimeString = null;
+                    base64KeySalt = null;
+                    //KeyInfo must only contain visible printing characters
+                    //and 40 char long, as its is the base64representation of concatenated Key and Salt
+                    var pospipe1 = keyInfo.IndexOf(PIPE);
+                    if (pospipe1 > 0)
+                    {
+                        base64KeySalt = keyInfo.Slice(0, pospipe1).ToString();
+                        //find lifetime and mki
+                        //both may be omitted, but mki is recognized by a colon
+                        //usually lifetime comes before mki, if specified
+                        var afterFirstPipe = pospipe1 + 1;
+                        var keyInfoTail = keyInfo.Slice(afterFirstPipe);
+                        var relativeColon = keyInfoTail.IndexOf(COLON);
+                        var relativePipe = keyInfoTail.IndexOf(PIPE);
+                        var posclnmki = relativeColon == -1 ? -1 : afterFirstPipe + relativeColon;
+                        var pospipe2 = relativePipe == -1 ? -1 : afterFirstPipe + relativePipe;
+
+                        if (posclnmki > 0 && pospipe2 < 0)
+                        {
+                            mkiValue = keyInfo.Slice(pospipe1 + 1, posclnmki - pospipe1 - 1).ToString();
+                            mkiLen = keyInfo.Slice(posclnmki + 1).ToString();
+                        }
+                        else if (posclnmki > 0 && pospipe2 < posclnmki)
+                        {
+                            lifeTimeString = keyInfo.Slice(pospipe1 + 1, pospipe2 - pospipe1 - 1).ToString();
+                            mkiValue = keyInfo.Slice(pospipe2 + 1, posclnmki - pospipe2 - 1).ToString();
+                            mkiLen = keyInfo.Slice(posclnmki + 1).ToString();
+                        }
+                        else if (posclnmki > 0 && pospipe2 > posclnmki)
+                        {
+                            mkiValue = keyInfo.Slice(pospipe1 + 1, posclnmki - pospipe1 - 1).ToString();
+                            mkiLen = keyInfo.Slice(posclnmki + 1, pospipe2 - posclnmki - 1).ToString();
+                            lifeTimeString = keyInfo.Slice(pospipe2 + 1).ToString();
+                        }
+                        else if (posclnmki < 0 && pospipe2 < 0)
+                        {
+                            lifeTimeString = keyInfo.Slice(pospipe1 + 1).ToString();
+                        }
+                        else if (posclnmki < 0 && pospipe2 > 0)
+                        {
+                            return false;
+                        }
+                    }
+                    else
+                    {
+                        base64KeySalt = keyInfo.ToString();
+                    }
+
+                    return true;
+                }
+
                 if (!string.IsNullOrWhiteSpace(keyParamString))
                 {
-                    string p = keyParamString.Trim();
-                    if (p.StartsWith(KEY_METHOD))
+                    var p = keyParamString.AsSpan().Trim();
+                    if (p.StartsWith(KEY_METHOD, StringComparison.Ordinal))
                     {
-                        string sKeyMethod = KEY_METHOD;
                         int poscln = p.IndexOf(COLON);
-                        if (poscln == sKeyMethod.Length)
+                        if (poscln == KEY_METHOD.Length)
                         {
-                            string sKeyInfo = p.Substring(poscln + 1);
-                            if (!sKeyInfo.Contains(";"))
+                            var sKeyInfo = p.Slice(poscln + 1);
+                            if (!sKeyInfo.Contains(SEMI_COLON))
                             {
-                                if ((!checkValidKeyInfoCharacters(sKeyInfo))
-                                    || (!parseKeyInfo(sKeyInfo, out var sMkiVal, out var sMkiLen, out var sLifeTime, out var sBase64KeySalt)))
+                                if ((!CheckValidKeyInfoCharacters(sKeyInfo))
+                                    || (!ParseKeyInfo(sKeyInfo, out var sMkiVal, out var sMkiLen, out var sLifeTime, out var sBase64KeySalt)))
                                 {
                                     return false;
                                 }
@@ -296,8 +366,8 @@ public static bool TryParse(string keyParamString, out KeyParameter keyParam, Cr
 
                                 if (!string.IsNullOrWhiteSpace(sMkiVal) && !string.IsNullOrWhiteSpace(sMkiLen))
                                 {
-                                    if (!uint.TryParse(sMkiVal, out uint mkiValue)
-                                        || !uint.TryParse(sMkiLen, out uint mkiLen)
+                                    if (!uint.TryParse(sMkiVal, out var mkiValue)
+                                        || !uint.TryParse(sMkiLen, out var mkiLen)
                                         || !(mkiLen > 0 && mkiLen <= 128))
                                     {
                                         keyParam = null;
@@ -312,7 +382,7 @@ public static bool TryParse(string keyParamString, out KeyParameter keyParam, Cr
                                 {
                                     if (sLifeTime.Contains("^"))
                                     {
-                                        if (!TryParseLifeTimeString(sLifeTime, out ulong lifeTime))
+                                        if (!TryParseLifeTimeString(sLifeTime, out var lifeTime))
                                         {
                                             keyParam = null;
                                             return false;
@@ -322,7 +392,7 @@ public static bool TryParse(string keyParamString, out KeyParameter keyParam, Cr
                                     }
                                     else
                                     {
-                                        if (!uint.TryParse(sLifeTime, out uint lifeTime)
+                                        if (!uint.TryParse(sLifeTime, out var lifeTime)
                                             || !IsValidLifeTime(lifeTime))
                                         {
                                             keyParam = null;
@@ -411,18 +481,6 @@ private static bool parseKeySaltBase64(CryptoSuites cryptoSuite, string base64Ke
                 return true;
             }
 
-            private static bool checkValidKeyInfoCharacters(string keyInfo)
-            {
-                foreach (char c in keyInfo)
-                {
-                    if (c < 0x21 || c > 0x7e)
-                    {
-                        return false;
-                    }
-                }
-                return true;
-            }
-
             private static bool IsValidLifeTime(ulong value)
             {
                 return value >= 2 && (value & (value - 1)) == 0;
@@ -442,13 +500,13 @@ private static bool TryParseLifeTimeString(string lifeTimeString, out ulong life
             {
                 lifeTime = 0;
 
-                if (string.IsNullOrWhiteSpace(lifeTimeString) || !lifeTimeString.StartsWith("2^"))
+                var lifeTimeSpan = lifeTimeString.AsSpan().Trim();
+                if (lifeTimeSpan.IsEmpty || !lifeTimeSpan.StartsWith("2^", StringComparison.Ordinal))
                 {
                     return false;
                 }
 
-                string exponentPart = lifeTimeString.Substring(2);
-                if (!ulong.TryParse(exponentPart, out ulong exponent) || exponent < 1 || exponent >= 64)
+                if (!ulong.TryParse(lifeTimeSpan.Slice(2), out var exponent) || exponent < 1 || exponent >= 64)
                 {
                     return false;
                 }
@@ -457,58 +515,6 @@ private static bool TryParseLifeTimeString(string lifeTimeString, out ulong life
                 return true;
             }
 
-            private static bool parseKeyInfo(string keyInfo, out string mkiValue, out string mkiLen, out string lifeTimeString, out string base64KeySalt)
-            {
-                mkiValue = null;
-                mkiLen = null;
-                lifeTimeString = null;
-                base64KeySalt = null;
-                //KeyInfo must only contain visible printing characters
-                //and 40 char long, as its is the base64representation of concatenated Key and Salt
-                int pospipe1 = keyInfo.IndexOf(PIPE);
-                if (pospipe1 > 0)
-                {
-                    base64KeySalt = keyInfo.Substring(0, pospipe1);
-                    //find lifetime and mki
-                    //both may be omitted, but mki is recognized by a colon
-                    //usually lifetime comes before mki, if specified
-                    int posclnmki = keyInfo.IndexOf(COLON, pospipe1 + 1);
-                    int pospipe2 = keyInfo.IndexOf(PIPE, pospipe1 + 1);
-
-                    if (posclnmki > 0 && pospipe2 < 0)
-                    {
-                        mkiValue = keyInfo.Substring(pospipe1 + 1, posclnmki - pospipe1 - 1);
-                        mkiLen = keyInfo.Substring(posclnmki + 1);
-                    }
-                    else if (posclnmki > 0 && pospipe2 < posclnmki)
-                    {
-                        lifeTimeString = keyInfo.Substring(pospipe1 + 1, pospipe2 - pospipe1 - 1);
-                        mkiValue = keyInfo.Substring(pospipe2 + 1, posclnmki - pospipe2 - 1);
-                        mkiLen = keyInfo.Substring(posclnmki + 1);
-                    }
-                    else if (posclnmki > 0 && pospipe2 > posclnmki)
-                    {
-                        mkiValue = keyInfo.Substring(pospipe1 + 1, posclnmki - pospipe1 - 1);
-                        mkiLen = keyInfo.Substring(posclnmki + 1, pospipe2 - posclnmki - 1);
-                        lifeTimeString = keyInfo.Substring(pospipe2 + 1);
-                    }
-                    else if (posclnmki < 0 && pospipe2 < 0)
-                    {
-                        lifeTimeString = keyInfo.Substring(pospipe1 + 1);
-                    }
-                    else if (posclnmki < 0 && pospipe2 > 0)
-                    {
-                        return false;
-                    }
-                }
-                else
-                {
-                    base64KeySalt = keyInfo;
-                }
-
-                return true;
-            }
-
             public static KeyParameter CreateNew(CryptoSuites cryptoSuite, string key = null, string salt = null)
             {
                 switch (cryptoSuite)
@@ -719,29 +725,27 @@ public static bool TryParse(string sessionParam, out SessionParameter result, Cr
                     return true;
                 }
 
-                string p = sessionParam.Trim();
+                var p = sessionParam.AsSpan().Trim();
                 SessionParameter.SrtpSessionParams paramType = SrtpSessionParams.unknown;
-                if (p.StartsWith(KDR_PREFIX))
+                if (p.StartsWith(KDR_PREFIX, StringComparison.Ordinal))
                 {
-                    string sKdr = p.Substring(KDR_PREFIX.Length);
-                    if (uint.TryParse(sKdr, out uint kdr))
+                    if (uint.TryParse(p.Slice(KDR_PREFIX.Length), out var kdr))
                     {
                         result = new SessionParameter(SrtpSessionParams.kdr) { Kdr = kdr };
                         return true;
                     }
                 }
-                else if (p.StartsWith(WSH_PREFIX))
+                else if (p.StartsWith(WSH_PREFIX, StringComparison.Ordinal))
                 {
-                    string sWsh = p.Substring(WSH_PREFIX.Length);
-                    if (uint.TryParse(sWsh, out uint wsh))
+                    if (uint.TryParse(p.Slice(WSH_PREFIX.Length), out var wsh))
                     {
                         result = new SessionParameter(SrtpSessionParams.wsh) { Wsh = wsh };
                         return true;
                     }
                 }
-                else if (p.StartsWith(FEC_KEY_PREFIX))
+                else if (p.StartsWith(FEC_KEY_PREFIX, StringComparison.Ordinal))
                 {
-                    string sFecKey = p.Substring(FEC_KEY_PREFIX.Length);
+                    var sFecKey = p.Slice(FEC_KEY_PREFIX.Length).ToString();
                     if (!KeyParameter.TryParse(sFecKey, out var fecKey, cryptoSuite))
                     {
                         return false;
@@ -749,9 +753,9 @@ public static bool TryParse(string sessionParam, out SessionParameter result, Cr
                     result = new SessionParameter(SrtpSessionParams.fec_key) { FecKey = fecKey };
                     return true;
                 }
-                else if (p.StartsWith(FEC_ORDER_PREFIX))
+                else if (p.StartsWith(FEC_ORDER_PREFIX, StringComparison.Ordinal))
                 {
-                    string sFecOrder = p.Substring(FEC_ORDER_PREFIX.Length);
+                    var sFecOrder = p.Slice(FEC_ORDER_PREFIX.Length).ToString();
                     if (!s_fecTypesLookup.TryGetValue(sFecOrder, out var fecOrder))
                     {
                         return false;
@@ -762,7 +766,8 @@ public static bool TryParse(string sessionParam, out SessionParameter result, Cr
                 }
                 else
                 {
-                    if (!Enum.TryParse<SrtpSessionParams>(p, out paramType) || paramType.ToString() != p)
+                    var paramString = p.ToString();
+                    if (!Enum.TryParse<SrtpSessionParams>(paramString, out paramType) || paramType.ToString() != paramString)
                     {
                         return false;
                     }
@@ -844,21 +849,22 @@ public override string ToString()
                 return null;
             }
 
-            string s = CRYPTO_ATTRIBUE_PREFIX + this.Tag + WHITE_SPACE + this.CryptoSuite.ToString() + WHITE_SPACE;
+            var s = new StringBuilder();
+            s.Append(CRYPTO_ATTRIBUE_PREFIX).Append(this.Tag).Append(WHITE_SPACE).Append(this.CryptoSuite).Append(WHITE_SPACE);
             for (int i = 0; i < this.KeyParams.Count; i++)
             {
                 if (i > 0)
                 {
-                    s += SEMI_COLON;
+                    s.Append(SEMI_COLON);
                 }
 
-                s += this.KeyParams[i].ToString();
+                s.Append(this.KeyParams[i].ToString());
             }
             if (this.SessionParam != null)
             {
-                s += WHITE_SPACE + this.SessionParam.ToString();
+                s.Append(WHITE_SPACE).Append(this.SessionParam.ToString());
             }
-            return s;
+            return s.ToString();
         }
 
         public static SDPSecurityDescription Parse(string cryptoLine)
@@ -884,50 +890,60 @@ public static bool TryParse(string cryptoLine, out SDPSecurityDescription securi
                 return false;
             }
 
-            string sCryptoValue = cryptoLine.Substring(cryptoLine.IndexOf(COLON) + 1);
+            var sCryptoValue = cryptoLine.AsSpan(cryptoLine.IndexOf(COLON) + 1);
 
             securityDescription = new SDPSecurityDescription();
-            string[] sCryptoParts = sCryptoValue.Split(WHITE_SPACES, StringSplitOptions.RemoveEmptyEntries);
+            Span<Range> sCryptoPartRanges = stackalloc Range[5];
+            var sCryptoPartCount = sCryptoValue.SplitAny(sCryptoPartRanges, WHITE_SPACES.AsSpan(), StringSplitOptions.RemoveEmptyEntries);
             if (sCryptoValue.Length < 2)
             {
                 return false;
             }
 
-            if (!uint.TryParse(sCryptoParts[0], out var tag))
+            if (sCryptoPartCount < 2)
             {
                 return false;
             }
-            securityDescription.Tag = tag;
 
-            if (!s_cryptoSuiteLookup.TryGetValue(sCryptoParts[1], out var cryptoSuite))
+            if (!uint.TryParse(sCryptoValue[sCryptoPartRanges[0]], out var tag))
             {
                 return false;
             }
-            securityDescription.CryptoSuite = cryptoSuite;
+            securityDescription.Tag = tag;
 
-            if (sCryptoParts.Length < 3)
+            if (!s_cryptoSuiteLookup.TryGetValue(sCryptoValue[sCryptoPartRanges[1]].ToString(), out var cryptoSuite))
             {
                 return false;
             }
+            securityDescription.CryptoSuite = cryptoSuite;
 
-            string[] sKeyParams = sCryptoParts[2].Split(SEMI_COLON);
-            if (sKeyParams.Length < 1)
+            if (sCryptoPartCount < 3)
             {
-                securityDescription = null;
                 return false;
             }
-            foreach (string kp in sKeyParams)
+
+            var sKeyParams = sCryptoValue[sCryptoPartRanges[2]];
+            var hasKeyParam = false;
+            foreach (var keyParamRange in sKeyParams.Split(SEMI_COLON))
             {
-                if (!KeyParameter.TryParse(kp, out var keyParam, securityDescription.CryptoSuite))
+                hasKeyParam = true;
+                if (!KeyParameter.TryParse(sKeyParams[keyParamRange].ToString(), out var keyParam, securityDescription.CryptoSuite))
                 {
                     securityDescription = null;
                     return false;
                 }
                 securityDescription.KeyParams.Add(keyParam);
             }
-            if (sCryptoParts.Length > 3)
+
+            if (!hasKeyParam)
+            {
+                securityDescription = null;
+                return false;
+            }
+
+            if (sCryptoPartCount > 3)
             {
-                if (!SessionParameter.TryParse(sCryptoParts[3], out var sessionParam, securityDescription.CryptoSuite))
+                if (!SessionParameter.TryParse(sCryptoValue[sCryptoPartRanges[3]].ToString(), out var sessionParam, securityDescription.CryptoSuite))
                 {
                     securityDescription = null;
                     return false;
diff --git a/src/SIPSorcery/net/SDP/SDPTypes.cs b/src/SIPSorcery/net/SDP/SDPTypes.cs
index 635bc712d..f577e1c1b 100644
--- a/src/SIPSorcery/net/SDP/SDPTypes.cs
+++ b/src/SIPSorcery/net/SDP/SDPTypes.cs
@@ -72,18 +72,18 @@ public static bool IsMediaStreamStatusAttribute(string attributeString, out Medi
         }
         else
         {
-            switch (attributeString.ToLower())
+            switch (attributeString)
             {
-                case SEND_RECV_ATTRIBUTE:
+                case var _ when SEND_RECV_ATTRIBUTE.Equals(attributeString, StringComparison.OrdinalIgnoreCase):
                     mediaStreamStatus = MediaStreamStatusEnum.SendRecv;
                     return true;
-                case SEND_ONLY_ATTRIBUTE:
+                case var _ when SEND_ONLY_ATTRIBUTE.Equals(attributeString, StringComparison.OrdinalIgnoreCase):
                     mediaStreamStatus = MediaStreamStatusEnum.SendOnly;
                     return true;
-                case RECV_ONLY_ATTRIBUTE:
+                case var _ when RECV_ONLY_ATTRIBUTE.Equals(attributeString, StringComparison.OrdinalIgnoreCase):
                     mediaStreamStatus = MediaStreamStatusEnum.RecvOnly;
                     return true;
-                case INACTIVE_ATTRIBUTE:
+                case var _ when INACTIVE_ATTRIBUTE.Equals(attributeString, StringComparison.OrdinalIgnoreCase):
                     mediaStreamStatus = MediaStreamStatusEnum.Inactive;
                     return true;
                 default:
diff --git a/src/SIPSorcery/net/STUN/STUNAppState.cs b/src/SIPSorcery/net/STUN/STUNAppState.cs
index 715ec84bf..7b20c1714 100644
--- a/src/SIPSorcery/net/STUN/STUNAppState.cs
+++ b/src/SIPSorcery/net/STUN/STUNAppState.cs
@@ -40,7 +40,7 @@ public static string PrintBuffer(byte[] buffer)
 
                 if (byteStr.Length == 1)
                 {
-                    bufferStr += "0" + byteStr;
+                    bufferStr += $"0{byteStr}";
                 }
                 else
                 {
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNAddressAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNAddressAttribute.cs
index 620b267df..0fb559f68 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNAddressAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNAddressAttribute.cs
@@ -95,7 +95,7 @@ public override int ToByteBuffer(byte[] buffer, int startIndex)
 
         public override string ToString()
         {
-            string attrDescrStr = "STUN Attribute: " + base.AttributeType + ", address=" + Address.ToString() + ", port=" + Port + ".";
+            string attrDescrStr = $"STUN Attribute: {base.AttributeType}, address={Address.ToString()}, port={Port}.";
 
             return attrDescrStr;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNAttribute.cs
index 8df861b5b..74dd29cca 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNAttribute.cs
@@ -220,7 +220,7 @@ public static List<STUNAttribute> ParseMessageAttributes(byte[] buffer, int star
 
                     attributes.Add(attribute);
 
-                    // Attributes start on 32 bit word boundaries so where an attribute length is not a multiple of 4 it gets padded. 
+                    // Attributes start on 32 bit word boundaries so where an attribute length is not a multiple of 4 it gets padded.
                     int padding = (stunAttributeLength % 4 != 0) ? 4 - (stunAttributeLength % 4) : 0;
 
                     startAttIndex = startAttIndex + 4 + stunAttributeLength + padding;
@@ -258,7 +258,7 @@ public virtual int ToByteBuffer(byte[] buffer, int startIndex)
 
         public new virtual string ToString()
         {
-            string attrDescrString = "STUN Attribute: " + AttributeType.ToString() + ", length=" + PaddedLength + ".";
+            string attrDescrString = $"STUN Attribute: {AttributeType.ToString()}, length={PaddedLength}.";
 
             return attrDescrString;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNChangeRequestAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNChangeRequestAttribute.cs
index 94608dfad..b41738deb 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNChangeRequestAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNChangeRequestAttribute.cs
@@ -53,7 +53,7 @@ public STUNChangeRequestAttribute(byte[] attributeValue)
 
         public override string ToString()
         {
-            string attrDescrStr = "STUN Attribute: " + STUNAttributeTypesEnum.ChangeRequest.ToString() + ", key byte=" + m_changeRequestByte.ToString("X") + ", change address=" + ChangeAddress + ", change port=" + ChangePort + ".";
+            string attrDescrStr = $"STUN Attribute: {STUNAttributeTypesEnum.ChangeRequest.ToString()}, key byte={m_changeRequestByte.ToString("X")}, change address={ChangeAddress}, change port={ChangePort}.";
 
             return attrDescrStr;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNConnectionIdAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNConnectionIdAttribute.cs
index 78244fd7e..bce3d091c 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNConnectionIdAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNConnectionIdAttribute.cs
@@ -44,7 +44,7 @@ public STUNConnectionIdAttribute(uint connectionId)
 
         public override string ToString()
         {
-            string attrDescrStr = "STUN CONNECTION_ID Attribute: value=" + ConnectionId + ".";
+            string attrDescrStr = $"STUN CONNECTION_ID Attribute: value={ConnectionId}.";
 
             return attrDescrStr;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNErrorCodeAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNErrorCodeAttribute.cs
index 097486d2d..709af72a1 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNErrorCodeAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNErrorCodeAttribute.cs
@@ -60,7 +60,7 @@ private static byte[] BuildValue(int errorCode, string reasonPhrase)
 
         public override string ToString()
         {
-            string attrDescrStr = "STUN ERROR_CODE_ADDRESS Attribute: error code=" + ErrorCode + ", reason phrase=" + ReasonPhrase + ".";
+            string attrDescrStr = $"STUN ERROR_CODE_ADDRESS Attribute: error code={ErrorCode}, reason phrase={ReasonPhrase}.";
 
             return attrDescrStr;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNAttributes/STUNXORAddressAttribute.cs b/src/SIPSorcery/net/STUN/STUNAttributes/STUNXORAddressAttribute.cs
index e76a7b1e9..544256c42 100644
--- a/src/SIPSorcery/net/STUN/STUNAttributes/STUNXORAddressAttribute.cs
+++ b/src/SIPSorcery/net/STUN/STUNAttributes/STUNXORAddressAttribute.cs
@@ -133,7 +133,7 @@ public override int ToByteBuffer(byte[] buffer, int startIndex)
 
         public override string ToString()
         {
-            string attrDescrStr = "STUN XOR_MAPPED_ADDRESS Attribute: " + base.AttributeType + ", address=" + Address.ToString() + ", port=" + Port + ".";
+            string attrDescrStr = $"STUN XOR_MAPPED_ADDRESS Attribute: {base.AttributeType}, address={Address.ToString()}, port={Port}.";
 
             return attrDescrStr;
         }
diff --git a/src/SIPSorcery/net/STUN/STUNMessage.cs b/src/SIPSorcery/net/STUN/STUNMessage.cs
index 2bdcdd541..ebde01549 100644
--- a/src/SIPSorcery/net/STUN/STUNMessage.cs
+++ b/src/SIPSorcery/net/STUN/STUNMessage.cs
@@ -198,13 +198,13 @@ public byte[] ToByteBuffer(byte[] messageIntegrityKey, bool addFingerprint)
             return buffer;
         }
 
-        public new string ToString()
+        public override string ToString()
         {
-            string messageDescr = "STUN Message: " + Header.MessageType.ToString() + ", length=" + Header.MessageLength;
+            string messageDescr = $"STUN Message: {Header.MessageType.ToString()}, length={Header.MessageLength}";
 
             foreach (STUNAttribute attribute in Attributes)
             {
-                messageDescr += "\n " + attribute.ToString();
+                messageDescr += $"\n {attribute.ToString()}";
             }
 
             return messageDescr;
diff --git a/src/SIPSorcery/net/WebRTC/RTCDataChannel.cs b/src/SIPSorcery/net/WebRTC/RTCDataChannel.cs
index 8a0d0b570..c4b44b429 100644
--- a/src/SIPSorcery/net/WebRTC/RTCDataChannel.cs
+++ b/src/SIPSorcery/net/WebRTC/RTCDataChannel.cs
@@ -134,8 +134,7 @@ public void send(string message)
         {
             if (message != null && Encoding.UTF8.GetByteCount(message) > _transport.maxMessageSize)
             {
-                throw new ApplicationException($"Data channel {label} was requested to send data of length {Encoding.UTF8.GetByteCount(message)} " +
-                    $" that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
+                throw new ApplicationException($"Data channel {label} was requested to send data of length {Encoding.UTF8.GetByteCount(message)}  that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
             }
             else if (_transport.state != RTCSctpTransportState.Connected)
             {
@@ -173,8 +172,7 @@ public void send(byte[] data, int offset = 0, int count = -1)
 
             if (effectiveCount > _transport.maxMessageSize)
             {
-                throw new ApplicationException($"Data channel {label} was requested to send data of length {effectiveCount} " +
-                    $" that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
+                throw new ApplicationException($"Data channel {label} was requested to send data of length {effectiveCount}  that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
             }
             else if (_transport.state != RTCSctpTransportState.Connected)
             {
diff --git a/src/SIPSorcery/net/WebRTC/RTCPeerConnection.cs b/src/SIPSorcery/net/WebRTC/RTCPeerConnection.cs
index 4c2b39b72..80866db1c 100644
--- a/src/SIPSorcery/net/WebRTC/RTCPeerConnection.cs
+++ b/src/SIPSorcery/net/WebRTC/RTCPeerConnection.cs
@@ -1876,12 +1876,13 @@ private bool DoDtlsHandshake(DtlsSrtpTransport dtlsHandle)
             }
             else
             {
-                logger.LogDebug($"RTCPeerConnection DTLS handshake result {handshakeResult}, is handshake complete {dtlsHandle.IsHandshakeComplete()}.");
+                logger.LogDebug("RTCPeerConnection DTLS handshake result {HandshakeResult}, is handshake complete {IsHandshakeComplete}.",
+                    handshakeResult, dtlsHandle.IsHandshakeComplete());
 
                 var expectedFp = RemotePeerDtlsFingerprint;
                 var remoteFingerprint = DtlsUtils.Fingerprint(expectedFp.algorithm, dtlsHandle.GetRemoteCertificate().GetCertificateAt(0));
 
-                if (remoteFingerprint.value?.ToUpper() != expectedFp.value?.ToUpper())
+                if (!string.Equals(remoteFingerprint.value, expectedFp.value, StringComparison.OrdinalIgnoreCase))
                 {
                     logger.LogWarning("RTCPeerConnection remote certificate fingerprint mismatch, expected {ExpectedFingerprint}, actual {RemoteFingerprint}.", expectedFp, remoteFingerprint);
                     Close("dtls fingerprint mismatch");
diff --git a/src/SIPSorcery/net/WebRTC/RTCSctpTransport.cs b/src/SIPSorcery/net/WebRTC/RTCSctpTransport.cs
index e8088412a..91739fcbe 100644
--- a/src/SIPSorcery/net/WebRTC/RTCSctpTransport.cs
+++ b/src/SIPSorcery/net/WebRTC/RTCSctpTransport.cs
@@ -380,8 +380,7 @@ public override void Send(string associationID, byte[] buffer, int offset, int l
         {
             if (length > maxMessageSize)
             {
-                throw new ApplicationException($"RTCSctpTransport was requested to send data of length {length} " +
-                    $" that exceeded the maximum allowed message size of {maxMessageSize}.");
+                throw new ApplicationException($"RTCSctpTransport was requested to send data of length {length}  that exceeded the maximum allowed message size of {maxMessageSize}.");
             }
 
             if (!_isClosed)
diff --git a/src/SIPSorceryMedia.FFmpeg/FFmpegCameraSource.cs b/src/SIPSorceryMedia.FFmpeg/FFmpegCameraSource.cs
index 3a85b3919..d6e68f960 100644
--- a/src/SIPSorceryMedia.FFmpeg/FFmpegCameraSource.cs
+++ b/src/SIPSorceryMedia.FFmpeg/FFmpegCameraSource.cs
@@ -42,9 +42,7 @@ public unsafe FFmpegCameraSource(Camera camera)
             string inputFormat = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "dshow"
                                     : RuntimeInformation.IsOSPlatform(OSPlatform.Linux) ? "v4l2"
                                     : RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "avfoundation"
-                                    : throw new NotSupportedException($"Cannot find adequate input format" +
-                                                $" - OSArchitecture:[{RuntimeInformation.OSArchitecture}]" +
-                                                $" - OSDescription:[{RuntimeInformation.OSDescription}]");
+                                    : throw new NotSupportedException($"Cannot find adequate input format - OSArchitecture:[{RuntimeInformation.OSArchitecture}] - OSDescription:[{RuntimeInformation.OSDescription}]");
 
             var _aVInputFormat = ffmpeg.av_find_input_format(inputFormat);
 
@@ -126,7 +124,7 @@ public bool RestrictCameraOptions(Func<Dictionary<string, string>, bool> optFilt
                                 );
 
             if (filtered is null)
-                logger.LogWarning($"No camera/input device options to be used.");
+                logger.LogWarning("No camera/input device options to be used.");
 
             return SetCameraDeviceOptions(filtered);
         }
diff --git a/src/SIPSorceryMedia.FFmpeg/FFmpegScreenSource.cs b/src/SIPSorceryMedia.FFmpeg/FFmpegScreenSource.cs
index 33d619155..168199353 100644
--- a/src/SIPSorceryMedia.FFmpeg/FFmpegScreenSource.cs
+++ b/src/SIPSorceryMedia.FFmpeg/FFmpegScreenSource.cs
@@ -28,7 +28,7 @@ public unsafe FFmpegScreenSource(string path, Rectangle rect, int frameRate = 20
                 {
                     ["offset_x"] = rect.X.ToString(),
                     ["offset_y"] = rect.Y.ToString(),
-                    ["video_size"] = $"{rect.Width.ToString()}X{rect.Height.ToString()}",
+                    ["video_size"] = $"{rect.Width}X{rect.Height}",
                     ["framerate"] = frameRate.ToString()
                 };
             }
@@ -37,7 +37,7 @@ public unsafe FFmpegScreenSource(string path, Rectangle rect, int frameRate = 20
                 inputFormat = "avfoundation";
                 options = new Dictionary<string, string>()
                 {
-                    ["vf"] = $"crop={rect.Width.ToString()}:{rect.Height.ToString()}:{rect.X.ToString()}:{rect.Y.ToString()}",
+                    ["vf"] = $"crop={rect.Width}:{rect.Height}:{rect.X}:{rect.Y}",
                     ["framerate"] = frameRate.ToString()
                 };
             }
@@ -47,7 +47,7 @@ public unsafe FFmpegScreenSource(string path, Rectangle rect, int frameRate = 20
                 //https://superuser.com/questions/1562228/how-to-specify-the-size-to-record-the-screen-with-ffmpeg
                 options = new Dictionary<string, string>()
                 {
-                    ["video_size"] = $"{rect.Width.ToString()}X{rect.Height.ToString()}",
+                    ["video_size"] = $"{rect.Width}X{rect.Height}",
                     ["grab_x"] = rect.X.ToString(),
                     ["grab_y"] = rect.Y.ToString(),
                     ["framerate"] = frameRate.ToString()
diff --git a/src/SIPSorceryMedia.FFmpeg/FfmpegInit.cs b/src/SIPSorceryMedia.FFmpeg/FfmpegInit.cs
index cc1c04eee..2b27a64e0 100644
--- a/src/SIPSorceryMedia.FFmpeg/FfmpegInit.cs
+++ b/src/SIPSorceryMedia.FFmpeg/FfmpegInit.cs
@@ -83,7 +83,7 @@ public static void Initialise(FfmpegLogLevelEnum? logLevel = null, String? libPa
 
             RegisterFFmpegBinaries(libPath);
 
-            logger.LogInformation($"FFmpeg version info: {ffmpeg.av_version_info()}");
+            logger.LogInformation("FFmpeg version info: {VersionInfo}", ffmpeg.av_version_info());
 
             if (logLevel.HasValue)
             {
@@ -105,10 +105,7 @@ internal static void SetFFmpegBinariesPath(string path)
             catch (Exception e)
             {
                 throw new DllNotFoundException(
-                    "Check the dependencies of FFmpeg libraries and make sure they are " +
-                    "searchable by the operating system's library loader."
-                    + "\nOn linux you can use 'ldd' & 'strace'."
-                    + "\nOn Windows you can use 'Dependencies'."
+                    $"Check the dependencies of FFmpeg libraries and make sure they are searchable by the operating system's library loader.\nOn linux you can use 'ldd' & 'strace'.\nOn Windows you can use 'Dependencies'."
                     , e);
             }
         }
@@ -124,12 +121,12 @@ internal static void RegisterFFmpegBinaries(String? libPath = null)
                 string ffmpegExecutable = "ffmpeg";
                 string? path = Environment.GetEnvironmentVariable("PATH")?
                     .Split([';'], StringSplitOptions.RemoveEmptyEntries)
-                    .Where(s => File.Exists(Path.Combine(s, ffmpegExecutable)) || File.Exists(Path.Combine(s, ffmpegExecutable  + ".exe")))
+                    .Where(s => File.Exists(Path.Combine(s, ffmpegExecutable)) || File.Exists(Path.Combine(s, $"{ffmpegExecutable}.exe")))
                     .FirstOrDefault();
 
                 if (path != null)
                 {
-                    logger.LogInformation($"FFmpeg binaries found in system path at: {path}");
+                    logger.LogInformation("FFmpeg binaries found in system path at: {Path}", path);
                     SetFFmpegBinariesPath(path);
                     return;
                 }
@@ -142,7 +139,7 @@ internal static void RegisterFFmpegBinaries(String? libPath = null)
                     var ffmpegBinaryPath = Path.Combine(current, probe);
                     if (Directory.Exists(ffmpegBinaryPath))
                     {
-                        logger.LogInformation($"FFmpeg binaries found in: {ffmpegBinaryPath}");
+                        logger.LogInformation("FFmpeg binaries found in: {Path}", ffmpegBinaryPath);
                         SetFFmpegBinariesPath(ffmpegBinaryPath);
                         return;
                     }
@@ -154,7 +151,7 @@ internal static void RegisterFFmpegBinaries(String? libPath = null)
             {
                 if (Directory.Exists(libPath))
                 {
-                    logger.LogInformation($"FFmpeg binaries path set to: {libPath}");
+                    logger.LogInformation("FFmpeg binaries path set to: {Path}", libPath);
                     SetFFmpegBinariesPath(libPath);
                     return;
                 }
diff --git a/src/SIPSorceryMedia.FFmpeg/Interop/MacOs/AvFoundation.cs b/src/SIPSorceryMedia.FFmpeg/Interop/MacOs/AvFoundation.cs
index 8a9e67ec4..6c5d44ee7 100644
--- a/src/SIPSorceryMedia.FFmpeg/Interop/MacOs/AvFoundation.cs
+++ b/src/SIPSorceryMedia.FFmpeg/Interop/MacOs/AvFoundation.cs
@@ -85,7 +85,7 @@ private static unsafe String GetAvFoundationLogsAboutDevicesList()
                                     {
                                         index = ln.IndexOf("]");
                                         string name = ln.Substring(index + 2);
-                                        string path = ln.Substring(1, index - 1) + ":";
+                                        string path = $"{ln.Substring(1, index - 1)}:";
 
                                         Monitor monitor = new Monitor
                                         {
@@ -149,7 +149,7 @@ private static unsafe String GetAvFoundationLogsAboutDevicesList()
                                     {
                                         index = ln.IndexOf("]");
                                         string name = ln.Substring(index+2);
-                                        string path = ln.Substring(1, index - 1) + ":";
+                                        string path = $"{ln.Substring(1, index - 1)}:";
 
                                         Camera camera = new Camera
                                         {
diff --git a/src/SIPSorceryMedia.Windows/WindowsVideoEndPoint.cs b/src/SIPSorceryMedia.Windows/WindowsVideoEndPoint.cs
index f6d58152c..a2ea1f064 100644
--- a/src/SIPSorceryMedia.Windows/WindowsVideoEndPoint.cs
+++ b/src/SIPSorceryMedia.Windows/WindowsVideoEndPoint.cs
@@ -231,11 +231,11 @@ private async Task<bool> InitialiseDevice(uint width, uint height, uint fps)
 
                 if (vidDevice == null)
                 {
-                    logger.LogWarning($"Could not find video capture device for specified ID {_videoDeviceID}, using default device.");
+                    logger.LogWarning("Could not find video capture device for specified ID {VideoDeviceId}, using default device.", _videoDeviceID);
                 }
                 else
                 {
-                    logger.LogInformation($"Video capture device {vidDevice.Name} selected.");
+                    logger.LogInformation("Video capture device {VideoDeviceName} selected.", vidDevice.Name);
                     mediaCaptureSettings.VideoDeviceId = vidDevice.Id;
                 }
             }
@@ -277,7 +277,8 @@ private async Task<bool> InitialiseDevice(uint width, uint height, uint fps)
             if (preferredFormat == null)
             {
                 // Still can't get what we want. Log a warning message and take the default.
-                logger.LogWarning($"The video capture device did not support the requested format (or better) {_width}x{_height} {fps}fps. Using default mode.");
+                logger.LogWarning("The video capture device did not support the requested format (or better) {Width}x{Height} {Fps}fps. Using default mode.",
+                    _width, _height, fps);
 
                 preferredFormat = colorFrameSource.SupportedFormats.First();
             }
@@ -455,7 +456,8 @@ public static async Task ListDevicesAndFormats()
                         var vidFmt = srcFmt.VideoFormat;
                         float vidFps = vidFmt.MediaFrameFormat.FrameRate.Numerator / vidFmt.MediaFrameFormat.FrameRate.Denominator;
                         string pixFmt = vidFmt.MediaFrameFormat.Subtype == MF_I420_PIXEL_FORMAT ? "I420" : vidFmt.MediaFrameFormat.Subtype;
-                        logger.LogDebug($"Video Capture device {vidCapDevice.Name} format {vidFmt.Width}x{vidFmt.Height} {vidFps:0.##}fps {pixFmt}");
+                        logger.LogDebug("Video Capture device {VideoDeviceName} format {Width}x{Height} {Fps:0.##}fps {PixelFormat}",
+                            vidCapDevice.Name, vidFmt.Width, vidFmt.Height, vidFps, pixFmt);
                     }
                 }
             }
@@ -478,7 +480,7 @@ public static async Task<List<VideoMediaFrameFormat>> GetDeviceFrameFormats(stri
             var vidCapDevices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
             foreach (var vidCapDevice in vidCapDevices)
             {
-                if(vidCapDevice.Name.ToLower() == deviceName.ToLower())
+                if(string.Equals(vidCapDevice.Name, deviceName, StringComparison.OrdinalIgnoreCase))
                 {
                     var mediaCaptureSettings = new MediaCaptureInitializationSettings()
                     {
@@ -685,7 +687,8 @@ private void PrintFrameSourceInfo(MediaFrameSource frameSource)
             string pixFmt = frameSource.CurrentFormat.Subtype;
             string deviceName = frameSource.Info.DeviceInformation.Name;
 
-            logger.LogInformation($"Video capture device {deviceName} successfully initialised: {width}x{height} {fps:0.##}fps pixel format {pixFmt}.");
+            logger.LogInformation("Video capture device {VideoDeviceName} successfully initialised: {Width}x{Height} {Fps:0.##}fps pixel format {PixelFormat}.",
+                deviceName, width, height, fps, pixFmt);
         }
 
         public void Dispose()
diff --git a/test/FFmpegConsoleApp/Program.cs b/test/FFmpegConsoleApp/Program.cs
old mode 100755
new mode 100644
diff --git a/test/unit/net/STUN/STUNUnitTest.cs b/test/unit/net/STUN/STUNUnitTest.cs
old mode 100755
new mode 100644