Bug 1940 - Clicky play when adjusting Pan or Volume TCP controls

src/AudioIO.cpp

@@ -5025,7 +5025,7 @@ int AudioIO::AudioCallback(const void *inputBuffer, void *outputBuffer,
                numSolo++;
 #endif
 
-         const WaveTrack **chans = (const WaveTrack **) alloca(numPlaybackChannels * sizeof(WaveTrack *));
+         WaveTrack **chans = (WaveTrack **) alloca(numPlaybackChannels * sizeof(WaveTrack *));
          float **tempBufs = (float **) alloca(numPlaybackChannels * sizeof(float *));
          for (unsigned int c = 0; c < numPlaybackChannels; c++)
          {
@@ -5041,7 +5041,7 @@ int AudioIO::AudioCallback(const void *inputBuffer, void *outputBuffer,
          decltype(framesPerBuffer) maxLen = 0;
          for (unsigned t = 0; t < numPlaybackTracks; t++)
          {
-            const WaveTrack *vt = mPlaybackTracks[t].get();
+            WaveTrack *vt = mPlaybackTracks[t].get();
 
             chans[chanCnt] = vt;
 
@@ -5140,7 +5140,7 @@ int AudioIO::AudioCallback(const void *inputBuffer, void *outputBuffer,
             if (cut) // no samples to process, they've been discarded
                continue;
 
-            for (int c = 0; c < chanCnt; c++)
+            if (len > 0) for (int c = 0; c < chanCnt; c++)
             {
                vt = chans[c];
 
@@ -5159,8 +5159,14 @@ int AudioIO::AudioCallback(const void *inputBuffer, void *outputBuffer,
                   if (mEmulateMixerOutputVol)
                      gain *= mMixerOutputVol;
 
-                  for(decltype(len) i = 0; i < len; i++)
+                  float oldGain = vt->GetOldChannelGain(0);
-                     outputFloats[numPlaybackChannels*i] += gain*tempBufs[c][i];
+                  if( gain != oldGain )
+                     vt->SetOldChannelGain(0, gain);
+                  wxASSERT(len > 0);
+                  float deltaGain = (gain - oldGain) / len;
+                  for (decltype(len) i = 0; i < len; i++)
+                     outputFloats[numPlaybackChannels*i] += (oldGain + deltaGain * i) *tempBufs[c][i];
+
                }
 
                if (vt->GetChannel() == Track::RightChannel ||
@@ -5177,8 +5183,13 @@ int AudioIO::AudioCallback(const void *inputBuffer, void *outputBuffer,
                   if (mEmulateMixerOutputVol)
                      gain *= mMixerOutputVol;
 
+                  float oldGain = vt->GetOldChannelGain(1);
+                  if (gain != oldGain)
+                     vt->SetOldChannelGain(1,gain);
+                  wxASSERT(len > 0);
+                  float deltaGain = (gain - oldGain) / len;
                   for(decltype(len) i = 0; i < len; i++)
-                     outputFloats[numPlaybackChannels*i+1] += gain*tempBufs[c][i];
+                     outputFloats[numPlaybackChannels*i+1] += (oldGain + deltaGain*i) *tempBufs[c][i];
                }
             }
 

src/AudioIO.h

@@ -156,7 +156,7 @@ struct AudioIOStartStreamOptions
 };
 
 struct TransportTracks {
-   WaveTrackConstArray playbackTracks;
+   WaveTrackArray playbackTracks;
    WaveTrackArray captureTracks;
 #ifdef EXPERIMENTAL_MIDI_OUT
    NoteTrackConstArray midiTracks;
@@ -691,7 +691,7 @@ private:
    ArrayOf<std::unique_ptr<RingBuffer>> mCaptureBuffers;
    WaveTrackArray      mCaptureTracks;
    ArrayOf<std::unique_ptr<RingBuffer>> mPlaybackBuffers;
-   WaveTrackConstArray mPlaybackTracks;
+   WaveTrackArray      mPlaybackTracks;
 
    ArrayOf<std::unique_ptr<Mixer>> mPlaybackMixers;
    volatile int        mStreamToken;

src/Track.cpp

@@ -1576,10 +1576,10 @@ bool TrackList::HasPendingTracks() const
 }
 
 #include "AudioIO.h"
-TransportTracks GetAllPlaybackTracks(const TrackList &trackList, bool selectedOnly, bool useMidi)
+TransportTracks GetAllPlaybackTracks(TrackList &trackList, bool selectedOnly, bool useMidi)
 {
    TransportTracks result;
-   result.playbackTracks = trackList.GetWaveTrackConstArray(selectedOnly);
+   result.playbackTracks = trackList.GetWaveTrackArray(selectedOnly);
 #ifdef EXPERIMENTAL_MIDI_OUT
    if (useMidi)
       result.midiTracks = trackList.GetNoteTrackConstArray(selectedOnly);

src/Track.h

@@ -893,6 +893,6 @@ class AUDACITY_DLL_API TrackFactory
 
 // global functions
 struct TransportTracks;
-TransportTracks GetAllPlaybackTracks(const TrackList &trackList, bool selectedOnly, bool useMidi = false);
+TransportTracks GetAllPlaybackTracks(TrackList &trackList, bool selectedOnly, bool useMidi = false);
 
 #endif

src/WaveTrack.cpp

@@ -153,6 +153,8 @@ void WaveTrack::Init(const WaveTrack &orig)
    mRate = orig.mRate;
    mGain = orig.mGain;
    mPan = orig.mPan;
+   mOldGain[0] = 0.0;
+   mOldGain[1] = 0.0;
    SetDefaultName(orig.GetDefaultName());
    SetName(orig.GetName());
    mDisplay = orig.mDisplay;
@@ -453,6 +455,18 @@ float WaveTrack::GetChannelGain(int channel) const
       return right*mGain;
 }
 
+float WaveTrack::GetOldChannelGain(int channel) const
+{
+   return mOldGain[channel%2];
+}
+
+void WaveTrack::SetOldChannelGain(int channel, float gain)
+{
+   mOldGain[channel % 2] = gain;
+}
+
+
+
 void WaveTrack::DoSetMinimized(bool isMinimized){
 
 #ifdef EXPERIMENTAL_HALF_WAVE

src/WaveTrack.h

@@ -138,6 +138,11 @@ private:
    // Takes gain and pan into account
    float GetChannelGain(int channel) const;
 
+   // Old gain is used in playback in linearly interpolating 
+   // the gain.
+   float GetOldChannelGain(int channel) const;
+   void SetOldChannelGain(int channel, float gain);
+
    void DoSetMinimized(bool isMinimized) override;
 
    int GetWaveColorIndex() const { return mWaveColorIndex; };
@@ -615,6 +620,7 @@ private:
    float         mGain;
    float         mPan;
    int           mWaveColorIndex;
+   float         mOldGain[2];
 
 
    //