Method ProcessStereo

libraries/lib-builtin-effects/SoundTouchBase.cpp:247–348

}

bool SoundTouchBase::ProcessStereo(soundtouch::SoundTouch *pSoundTouch,
   WaveTrack &orig, WaveTrack &outputTrack,
   sampleCount start, sampleCount end, const TimeWarper &warper)
{
   pSoundTouch->setSampleRate(
      static_cast<unsigned int>(orig.GetRate() + 0.5));

   auto channels = orig.Channels();
   auto &leftTrack = **channels.first++;
   auto &rightTrack = **channels.first;

   auto newChannels = outputTrack.Channels();
   auto &outputLeftTrack = **newChannels.first++;
   auto &outputRightTrack = **newChannels.first;

   //Get the length of the buffer (as double). len is
   //used simple to calculate a progress meter, so it is easier
   //to make it a double now than it is to do it later
   double len = (end - start).as_double();

   //Initiate a processing buffer.  This buffer will (most likely)
   //be shorter than the length of the track being processed.
   // Make soundTouchBuffer twice as big as MaxBlockSize for each channel,
   // because Soundtouch wants them interleaved, i.e., each
   // Soundtouch sample is left-right pair.
   auto maxBlockSize = orig.GetMaxBlockSize();
   {
      Floats leftBuffer{ maxBlockSize };
      Floats rightBuffer{ maxBlockSize };
      Floats soundTouchBuffer{ maxBlockSize * 2 };

      // Go through the track one stereo buffer at a time.
      // sourceSampleCount counts the sample at which the current buffer starts,
      // per channel.
      auto sourceSampleCount = start;
      while (sourceSampleCount < end) {
         auto blockSize = limitSampleBufferSize(
            orig.GetBestBlockSize(sourceSampleCount),
            end - sourceSampleCount
         );

         // Get the samples from the tracks and put them in the buffers.
         leftTrack.GetFloats((leftBuffer.get()), sourceSampleCount, blockSize);
         rightTrack
            .GetFloats((rightBuffer.get()), sourceSampleCount, blockSize);

         // Interleave into soundTouchBuffer.
         for (decltype(blockSize) index = 0; index < blockSize; index++) {
            soundTouchBuffer[index * 2] = leftBuffer[index];
            soundTouchBuffer[(index * 2) + 1] = rightBuffer[index];
         }

         //Add samples to SoundTouch
         pSoundTouch->putSamples(soundTouchBuffer.get(), blockSize);

         //Get back samples from SoundTouch
         unsigned int outputCount = pSoundTouch->numSamples();
         if (outputCount > 0)