fix: bypass voice processing only for stereo (#25)

ref: GetStream/stream-video-swift#1009

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Consolidated default audio constraints so tracks use sensible defaults
while still honoring user-specified audio settings

* **Bug Fixes**
  * Voice processing no longer forcibly bypassed by default
* Stereo playout preference now correctly aligns with voice processing
bypass state

* **Chores**
  * Updated copyright year to 2026
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: santhoshvai

ios/RCTWebRTC/Utils/AudioDeviceModule/AudioDeviceModule.swift

@@ -1,5 +1,5 @@
 //
-// Copyright © 2025 Stream.io Inc. All rights reserved.
+// Copyright © 2026 Stream.io Inc. All rights reserved.
 //
 
 import AudioToolbox
@@ -92,7 +92,7 @@ import WebRTC
                 return ".willReleaseAudioEngine(\(engine))"
 
             case .configureInputFromSource(let engine, let source, let destination, let format):
-                return ".configureInputFromSource(\(engine), source:\(source?.description ?? "nil"), destination:\(destination), format:\(format))"
+                return ".configureInputFromSource(\(engine), source:\(source), destination:\(destination), format:\(format))"
 
             case .configureOutputFromSource(let engine, let source, let destination, let format):
                 return ".configureOutputFromSource(\(engine), source:\(source), destination:\(destination?.description ?? "nil"), format:\(format))"
@@ -221,9 +221,6 @@ import WebRTC
 
         audioLevelsAdapter.subject = audioLevelSubject
         source.observer = self
-
-        source.isVoiceProcessingBypassed = true
-        isVoiceProcessingBypassedSubject.send(true)
     }
 
     /// Objective-C compatible convenience initializer.
@@ -255,6 +252,7 @@ import WebRTC
         /// sendAudio capability.
         _ = source.setRecordingAlwaysPreparedMode(false)
         source.prefersStereoPlayout = isPreferred
+        source.isVoiceProcessingBypassed = isPreferred
     }
 
     /// Starts or stops speaker playout on the ADM, retrying transient failures.

ios/RCTWebRTC/WebRTCModule+RTCMediaStream.m

@@ -30,6 +30,25 @@ - (void)setVideoEffectProcessor:(VideoEffectProcessor *)videoEffectProcessor
   objc_setAssociatedObject(self, @selector(videoEffectProcessor), videoEffectProcessor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }
 
+#pragma mark - Default Media Constraints
+
+/**
+ * Returns common optional constraints for improved audio quality.
+ * Ported from stream-video-swift DefaultRTCMediaConstraints.
+ * https://github.com/GetStream/stream-video-swift/blob/develop/Sources/StreamVideo/WebRTC/DefaultRTCMediaConstraints.swift
+ */
++ (NSDictionary *)commonOptionalConstraints {
+    return @{
+        @"DtlsSrtpKeyAgreement": kRTCMediaConstraintsValueTrue,
+        @"googAutoGainControl": kRTCMediaConstraintsValueTrue,
+        @"googNoiseSuppression": kRTCMediaConstraintsValueTrue,
+        @"googEchoCancellation": kRTCMediaConstraintsValueTrue,
+        @"googHighpassFilter": kRTCMediaConstraintsValueTrue,
+        @"googTypingNoiseDetection": kRTCMediaConstraintsValueTrue,
+        @"googAudioMirroring": kRTCMediaConstraintsValueFalse
+    };
+}
+
 #pragma mark - getUserMedia
 
 - (NSString *)convertBoolToString:(id)value {
@@ -45,19 +64,23 @@ - (NSString *)convertBoolToString:(id)value {
 - (RTCAudioTrack *)createAudioTrack:(NSDictionary *)constraints {
     NSString *trackId = [[NSUUID UUID] UUIDString];
     NSDictionary *audioConstraints = constraints[@"audio"];
-    NSMutableDictionary *optionalConstraints = [NSMutableDictionary dictionary];
-    optionalConstraints[@"googAutoGainControl"] = audioConstraints[@"autoGainControl"] != nil
-                                                      ? [self convertBoolToString:audioConstraints[@"autoGainControl"]]
-                                                      : @"true";
-    optionalConstraints[@"googNoiseSuppression"] =
-        audioConstraints[@"noiseSuppression"] != nil ? [self convertBoolToString:audioConstraints[@"noiseSuppression"]]
-                                                     : @"true";
-    optionalConstraints[@"googEchoCancellation"] =
-        audioConstraints[@"echoCancellation"] != nil ? [self convertBoolToString:audioConstraints[@"echoCancellation"]]
-                                                     : @"true";
-    optionalConstraints[@"googHighpassFilter"] = audioConstraints[@"highpassFilter"] != nil
-                                                     ? [self convertBoolToString:audioConstraints[@"highpassFilter"]]
-                                                     : @"true";
+
+    // Start with common optional constraints as defaults
+    NSMutableDictionary *optionalConstraints = [[[self class] commonOptionalConstraints] mutableCopy];
+
+    // Override with user-provided constraints if specified
+    if (audioConstraints[@"autoGainControl"] != nil) {
+        optionalConstraints[@"googAutoGainControl"] = [self convertBoolToString:audioConstraints[@"autoGainControl"]];
+    }
+    if (audioConstraints[@"noiseSuppression"] != nil) {
+        optionalConstraints[@"googNoiseSuppression"] = [self convertBoolToString:audioConstraints[@"noiseSuppression"]];
+    }
+    if (audioConstraints[@"echoCancellation"] != nil) {
+        optionalConstraints[@"googEchoCancellation"] = [self convertBoolToString:audioConstraints[@"echoCancellation"]];
+    }
+    if (audioConstraints[@"highpassFilter"] != nil) {
+        optionalConstraints[@"googHighpassFilter"] = [self convertBoolToString:audioConstraints[@"highpassFilter"]];
+    }
 
     RTCMediaConstraints *mediaConstraints =
         [[RTCMediaConstraints alloc] initWithMandatoryConstraints:nil optionalConstraints:optionalConstraints];