code: protected boolean isChunkReady(StreamingTrack streamingTrack, StreamingSample next) {
          long ts = nextSampleStartTime.get(streamingTrack);
          long cfst = nextChunkCreateStartTime.get(streamingTrack);
  
          return (ts >= cfst + 2 * streamingTrack.getTimescale());
          // chunk interleave of 2 seconds
      }
docs: Tests if the currently received samples for a given track
  are already a 'chunk' as we want to have it. The next
  sample will not be part of the chunk
  will be added to the fragment buffer later.
  
  @param streamingTrack track to test
  @param next           the lastest samples
  @return true if a chunk is to b e created.