Downsampler now utilizes a new downsampleReal function, will hopefully run in macOS 13.

Author: ConnorGibbons

Sources/SignalTools/Downsample.swift

@@ -117,13 +117,10 @@ public class Downsampler {
 
 }
 
-
 public func downsampleComplex(iqData: [DSPComplex], decimationFactor: Int, filter: [Float] = [0.5, 0.5]) -> [DSPComplex] {
     guard iqData.count > (filter.count - 1) else { // Less data than is needed to apply the filter, thus no output.
         return []
     }
-    let usableSamplesCount = iqData.count - (filter.count - 1) // Samples with enough proceeding samples to apply the filter.
-    // let outputCount = max(usableSamplesCount / decimationFactor, 1)
 
     var returnVector: [DSPComplex]
     var splitComplexData = DSPSplitComplex(realp: .allocate(capacity: iqData.count), imagp: .allocate(capacity: iqData.count))
@@ -134,8 +131,10 @@ public func downsampleComplex(iqData: [DSPComplex], decimationFactor: Int, filte
     vDSP.convert(interleavedComplexVector: iqData, toSplitComplexVector: &splitComplexData)
     let iBranchBufferPointer = UnsafeBufferPointer(start: splitComplexData.realp, count: iqData.count)
     let qBranchBufferPointer = UnsafeBufferPointer(start: splitComplexData.imagp, count: iqData.count)
-    var iBranchDownsampled = vDSP.downsample(iBranchBufferPointer, decimationFactor: decimationFactor, filter: filter)
-    var qBranchDownsampled = vDSP.downsample(qBranchBufferPointer, decimationFactor: decimationFactor, filter: filter)
+    let iBranchArray: [Float] = Array(iBranchBufferPointer)
+    let qBranchArray: [Float] = Array(qBranchBufferPointer)
+    var iBranchDownsampled = downsampleReal(data: iBranchArray, decimationFactor: decimationFactor, filter: filter)
+    var qBranchDownsampled = downsampleReal(data: qBranchArray, decimationFactor: decimationFactor, filter: filter)
     returnVector = .init(repeating: DSPComplex(real: 0, imag: 0), count: iBranchDownsampled.count)
     return iBranchDownsampled.withUnsafeMutableBufferPointer { iDownsampledBufferPointer in
         qBranchDownsampled.withUnsafeMutableBufferPointer { qDownsampledBufferPointer in
@@ -147,11 +146,8 @@ public func downsampleComplex(iqData: [DSPComplex], decimationFactor: Int, filte
 }
 
 public func downsampleReal(data: [Float], decimationFactor: Int, filter: [Float] = [0.5, 0.5]) -> [Float] {
-    return vDSP.downsample(data, decimationFactor: decimationFactor, filter: filter)
-}
-
-public func downsampleRealX(data: [Float], decimationFactor: Int, filter: [Float] = [0.5, 0.5]) -> [Float] {
-    let outputCount = data.count / decimationFactor
+    let usableSampleCount = data.count - (filter.count - 1)
+    let outputCount = Int(ceil(Double(usableSampleCount) / Double(decimationFactor)))
     var outputBuffer: [Float] = .init(repeating: 0.0, count: outputCount)
     var dataMutableCopy: [Float] = data
     var filterMutableCopy: [Float] = filter
@@ -160,3 +156,35 @@ public func downsampleRealX(data: [Float], decimationFactor: Int, filter: [Float
 
     return outputBuffer
 }
+
+public func downsampleComplexOLD(iqData: [DSPComplex], decimationFactor: Int, filter: [Float] = [0.5, 0.5]) -> [DSPComplex] {
+    guard iqData.count > (filter.count - 1) else { // Less data than is needed to apply the filter, thus no output.
+        return []
+    }
+    // let usableSamplesCount = iqData.count - (filter.count - 1) // Samples with enough proceeding samples to apply the filter.
+    // let outputCount = max(usableSamplesCount / decimationFactor, 1)
+    
+    var returnVector: [DSPComplex]
+    var splitComplexData = DSPSplitComplex(realp: .allocate(capacity: iqData.count), imagp: .allocate(capacity: iqData.count))
+    defer {
+        splitComplexData.realp.deallocate()
+        splitComplexData.imagp.deallocate()
+    }
+    vDSP.convert(interleavedComplexVector: iqData, toSplitComplexVector: &splitComplexData)
+    let iBranchBufferPointer = UnsafeBufferPointer(start: splitComplexData.realp, count: iqData.count)
+    let qBranchBufferPointer = UnsafeBufferPointer(start: splitComplexData.imagp, count: iqData.count)
+    var iBranchDownsampled = vDSP.downsample(iBranchBufferPointer, decimationFactor: decimationFactor, filter: filter)
+    var qBranchDownsampled = vDSP.downsample(qBranchBufferPointer, decimationFactor: decimationFactor, filter: filter)
+    returnVector = .init(repeating: DSPComplex(real: 0, imag: 0), count: iBranchDownsampled.count)
+    return iBranchDownsampled.withUnsafeMutableBufferPointer { iDownsampledBufferPointer in
+        qBranchDownsampled.withUnsafeMutableBufferPointer { qDownsampledBufferPointer in
+            let splitDownsampledData = DSPSplitComplex(realp: iDownsampledBufferPointer.baseAddress!, imagp: qDownsampledBufferPointer.baseAddress!)
+            vDSP.convert(splitComplexVector: splitDownsampledData, toInterleavedComplexVector: &returnVector)
+            return returnVector
+        }
+    }
+}
+
+public func downsampleRealOLD(data: [Float], decimationFactor: Int, filter: [Float] = [0.5, 0.5]) -> [Float] {
+    return vDSP.downsample(data, decimationFactor: decimationFactor, filter: filter)
+}

Tests/SignalToolsTests/SignalToolsTests.swift

@@ -149,9 +149,7 @@ class SignalToolsTests: XCTestCase {
         randomTapsCount = Int.random(in: 3...151) | 1
         print("Decimation factor: \(randomDecimationFactor) \nOutput sample rate: \(randomOutputSampleRate) \nInput sample rate: \(randomInputSampleRate) \nTaps count: \(randomTapsCount)")
         let testDataDownsampleFilter = try FIRFilter(type: .lowPass, cutoffFrequency: Double(Double(randomOutputSampleRate) / 2.0), sampleRate: randomInputSampleRate, tapsLength: randomTapsCount)
-        let downsampledOriginal = SignalTools.downsampleRealX(data: testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
-        return;
-        let downsampledvDSP = vDSP.downsample(testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
+        let downsampledFullPass = SignalTools.downsampleReal(data: testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
         let downsampler = Downsampler(inputSampleRate: randomInputSampleRate, outputSampleRate: randomOutputSampleRate, filter: testDataDownsampleFilter.getTaps())
         let randomlySplitData = randomlySplitArray(testData)
         var downsampledOutput: [Float] = []
@@ -160,12 +158,10 @@ class SignalToolsTests: XCTestCase {
             downsampledOutput.append(contentsOf: output!)
         }
 
-        XCTAssertTrue(valsAreClose(downsampledOutput, downsampledOriginal, threshold: 0.00001))
-        XCTAssertTrue(valsAreClose(downsampledvDSP, downsampledOriginal))
+        XCTAssertTrue(valsAreClose(downsampledOutput, downsampledFullPass, threshold: 0.00001))
     }
 
     func testComplexDownsamplerEquivalence() throws {
-        return
         let testData = randomComplexData
         let randomDecimationFactor = Int.random(in: 2...100)
         let randomOutputSampleRate = Int.random(in: 100...48000)
@@ -175,8 +171,8 @@ class SignalToolsTests: XCTestCase {
 
         let testDataDownsampleFilter = try FIRFilter(type: .lowPass, cutoffFrequency: Double(Double(randomOutputSampleRate) / 2.0), sampleRate: randomInputSampleRate, tapsLength: randomTapsCount)
 
-        let downsampledOriginal = SignalTools.downsampleComplex(iqData: testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
-        
+//        let downsampledOriginal = SignalTools.downsampleComplexOLD(iqData: testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
+        let downsampledFullPass = SignalTools.downsampleComplex(iqData: testData, decimationFactor: randomDecimationFactor, filter: testDataDownsampleFilter.getTaps())
         let downsampler = Downsampler(inputSampleRate: randomInputSampleRate, outputSampleRate: randomOutputSampleRate, filter: testDataDownsampleFilter.getTaps())
         let randomlySplitData = randomlySplitArray(testData)
         var downsampledOutput: [DSPComplex] = []
@@ -186,9 +182,8 @@ class SignalToolsTests: XCTestCase {
         }
 
         print(downsampledOutput.count)
-        print(downsampledOriginal.count)
 
-        XCTAssertTrue(valsAreClose(downsampledOutput, downsampledOriginal, threshold: 0.001))
+        XCTAssertTrue(valsAreClose(downsampledOutput, downsampledFullPass, threshold: 0.001))
     }
 
 }