Method TestDirectionChanges

src/VoiceKey.cpp:951–993

double VoiceKey::TestDirectionChanges(
   const WaveChannel & t, sampleCount start, sampleCount len)
{


   auto s = start;                                //Keep track of start
   auto originalLen = len;                        //Keep track of the length of block to process (its not the length of t)
   const auto blockSize = limitSampleBufferSize(
      t.GetMaxBlockSize(), len);               //Determine size of sampling buffer
   unsigned long directionchanges = 1;
   float lastval=float(0);
   int lastdirection=1;

   Floats buffer{ blockSize };       //Get a sampling buffer

   while(len > 0) {
      //Figure out how much to grab
      auto block = limitSampleBufferSize ( t.GetBestBlockSize(s), len );

      t.GetFloats(buffer.get(), s, block);                      //grab the block;

      if  (len == originalLen) {
         //The first time through, set stuff up special.
         lastval = buffer[0];
      }

      //Now, go through the block and calculate zero crossings


      for(decltype(block) i = 0; i< block; i++){

         if( sgn(buffer[i]-lastval) != lastdirection) {
            directionchanges++;
            lastdirection = sgn(buffer[i] - lastval);
         }
         lastval = buffer[i];

      }
      len -= block;
      s += block;
   }
   return (double)directionchanges/originalLen.as_double();
}