function createAVCSample(key, pts, dts, debug) {
  return {
    key: key,
    frame: false,
    pts: pts,
    dts: dts,
    units: [],
    debug: debug,
    length: 0
  };
}
Initializes a new init segment on the demuxer/remuxer interface. Needed for discontinuities/track-switches (or at stream start)
Resets all internal track instances of the demuxer.