Add a user-definable "grain size" to PhaseLockedVocoder (#43)

* Add a user-definable "grain size" to PhaseLockedVocoder

The size of the mincer in the DSP can be set on init of PhaseLockedVocoder in a range of 128...8192. A smaller value makes the sound crisper when the sample position is moved. But a greater mincer size might also be desirable because the spectral freeze changes audibly.

* Formatting

Author: maweibezahn

Sources/CSoundpipeAudioKit/Generators/PhaseLockedVocoderDSP.mm

@@ -3,6 +3,7 @@
 #include "SoundpipeDSPBase.h"
 #include "ParameterRamper.h"
 #include "Soundpipe.h"
+#include "CSoundpipeAudioKit.h"
 #include <vector>
 
 enum PhaseLockedVocoderParameter : AUParameterAddress {
@@ -16,6 +17,7 @@
     sp_mincer *mincer;
     sp_ftbl *ftbl;
     std::vector<float> wavetable;
+    int mincerSize = 2048;
 
     ParameterRamper positionRamp;
     ParameterRamper amplitudeRamp;
@@ -42,7 +44,7 @@ void init(int channelCount, double sampleRate) override {
         sp_ftbl_create(sp, &ftbl, wavetable.size());
         std::copy(wavetable.cbegin(), wavetable.cend(), ftbl->tbl);
         sp_mincer_create(&mincer);
-        sp_mincer_init(sp, mincer, ftbl, 2048);
+        sp_mincer_init(sp, mincer, ftbl, mincerSize);
     }
 
     void deinit() override {
@@ -56,7 +58,12 @@ void reset() override {
         if (!isInitialized) return;
         sp_mincer_destroy(&mincer);
         sp_mincer_create(&mincer);
-        sp_mincer_init(sp, mincer, ftbl, 2048);
+        sp_mincer_init(sp, mincer, ftbl, mincerSize);
+    }
+    
+    void setMincerSize(int size) {
+        mincerSize = size;
+        reset();
     }
 
     void process(FrameRange range) override {
@@ -73,6 +80,12 @@ void process(FrameRange range) override {
     }
 };
 
+void akPhaseLockedVocoderSetMincerSize(DSPRef dspRef, int size) {
+    auto dsp = dynamic_cast<PhaseLockedVocoderDSP *>(dspRef);
+    assert(dsp);
+    dsp->setMincerSize(size);
+}
+
 AK_REGISTER_DSP(PhaseLockedVocoderDSP, "minc")
 AK_REGISTER_PARAMETER(PhaseLockedVocoderParameterPosition)
 AK_REGISTER_PARAMETER(PhaseLockedVocoderParameterAmplitude)

Sources/CSoundpipeAudioKit/include/CSoundpipeAudioKit.h

@@ -13,4 +13,5 @@ void akCombFilterReverbSetLoopDuration(DSPRef dsp, float duration);
 void akConvolutionSetPartitionLength(DSPRef dsp, int length);
 void akFlatFrequencyResponseSetLoopDuration(DSPRef dsp, float duration);
 void akVariableDelaySetMaximumTime(DSPRef dsp, float maximumTime);
-CF_EXTERN_C_END
+void akPhaseLockedVocoderSetMincerSize(DSPRef dspRef, int size);
+CF_EXTERN_C_END

Sources/SoundpipeAudioKit/Generators/PhaseLockedVocoder.swift

@@ -4,6 +4,7 @@ import AudioKit
 import AudioKitEX
 import AVFoundation
 import CAudioKitEX
+import CSoundpipeAudioKit
 
 /// This is a phase locked vocoder. It has the ability to play back an audio
 /// file loaded into an ftable like a sampler would. Unlike a typical sampler,
@@ -69,16 +70,36 @@ public class PhaseLockedVocoder: Node {
         file: AVAudioFile,
         position: AUValue = positionDef.defaultValue,
         amplitude: AUValue = amplitudeDef.defaultValue,
-        pitchRatio: AUValue = pitchRatioDef.defaultValue
+        pitchRatio: AUValue = pitchRatioDef.defaultValue,
+        grainSize: Int32 = 2048
     ) {
         setupParameters()
 
         loadFile(file)
 
+        let safeGrainSize = roundUpToPowerOfTwo(grainSize)
+        akPhaseLockedVocoderSetMincerSize(au.dsp, safeGrainSize)
+
         self.position = position
         self.amplitude = amplitude
         self.pitchRatio = pitchRatio
     }
+
+    /// The grain size range is 128 - 8192 and it must be a power of two.
+    /// If it isn't one already, this function will round it up to the next power of two
+    /// (should we warn the user if they submit a value which is not in that range or is not a power of two?)
+    func roundUpToPowerOfTwo(_ value: Int32) -> Int32 {
+        let range: ClosedRange<Int32> = 128...8192
+        guard range.contains(value) else { return min(max(value, range.lowerBound), range.upperBound) }
+        var result = value - 1
+        result |= result >> 1
+        result |= result >> 2
+        result |= result >> 4
+        result |= result >> 8
+        result |= result >> 16
+        result += 1
+        return result
+    }
 
     /// Call this function after you are done with the node, to reset the au wavetable to prevent memory leaks
     public func dispose() {