constructor (flv, softVideo, opts = {}) {
    this.flv = flv
    this._opts = opts

    if (softVideo) { // soft decode
      this._softVideo = softVideo
    } else {
      this._remuxer = new FMP4Remuxer(this._demuxer.videoTrack, this._demuxer.audioTrack)
      this._mse = new MSE(null, {
        preferMMS:
          typeof opts.preferMMS === 'boolean' ? opts.preferMMS : !!opts.perferMMS /* perferMMS is typo, deprecated */
      })
      this._mse.bindMedia(flv.media)
    }
  }
@param {import('../index').Flv} flv
@param {Object} [softVideo]