Method GetSpectrogram

src/tracks/playabletrack/wavetrack/ui/SpectrumCache.cpp:606–716

}

bool WaveClipSpectrumCache::GetSpectrogram(
   const WaveChannelInterval &clip,
   const float*& spectrogram, SpectrogramSettings& settings,
   const sampleCount*& where, size_t numPixels, double t0,
   double pixelsPerSecond)

{
   auto &mSpecCache = mSpecCaches[clip.GetChannelIndex()];

   const auto sampleRate = clip.GetRate();
   const auto stretchRatio = clip.GetStretchRatio();
   const auto samplesPerPixel = sampleRate / pixelsPerSecond / stretchRatio;

   //Trim offset comparison failure forces spectrogram cache rebuild
   //and skip copying "unchanged" data after clip border was trimmed.
   bool match = mSpecCache && mSpecCache->leftTrim == clip.GetTrimLeft() &&
                mSpecCache->rightTrim == clip.GetTrimRight() &&
                mSpecCache->len > 0 &&
                mSpecCache->Matches(mDirty, samplesPerPixel, settings);

   if (match && mSpecCache->start == t0 && mSpecCache->len >= numPixels)
   {
      spectrogram = &mSpecCache->freq[0];
      where = &mSpecCache->where[0];

      return false;  //hit cache completely
   }

   // Caching is not implemented for reassignment, unless for
   // a complete hit, because of the complications of time reassignment
   if (settings.algorithm == SpectrogramSettings::algReassignment)
      match = false;

   // Free the cache when it won't cause a major stutter.
   // If the window size changed, we know there is nothing to be copied
   // If we zoomed out, or resized, we can give up memory. But not too much -
   // up to 2x extra is needed at the end of the clip to prevent stutter.
   if (mSpecCache->freq.capacity() > 2.1 * mSpecCache->freq.size() ||
       mSpecCache->windowSize*mSpecCache->zeroPaddingFactor <
       settings.WindowSize()*settings.ZeroPaddingFactor())
   {
      match = false;
      mSpecCache = std::make_unique<SpecCache>();
   }

   int oldX0 = 0;
   double correction = 0.0;

   int copyBegin = 0, copyEnd = 0;
   if (match) {
      WaveClipUIUtilities::findCorrection(
         mSpecCache->where, mSpecCache->len, numPixels, t0, sampleRate,
         stretchRatio, samplesPerPixel, oldX0, correction);
      // Remember our first pixel maps to oldX0 in the old cache,
      // possibly out of bounds.
      // For what range of pixels can data be copied?
      int oldLen = mSpecCache->len;
      copyBegin = std::min(oldLen, std::max(0, -oldX0));