fix (startTime, discontinuity, contiguous) {
    this._fixer.fix(startTime, discontinuity, contiguous)
    return {
      videoTrack: this.videoTrack,
      audioTrack: this.audioTrack,
      metadataTrack: this.metadataTrack
    }
  }
@param {number} [startTime=0]
@param {boolean} [discontinuity=false]
@param {boolean} [contiguous=true]
@returns {DemuxResult}