static opus (track) {
    const opusAudioDescription = new Uint8Array([
      0x00, 0x00, 0x00, // version
      0x00, 0x00, 0x00, // reserved
      0x00, 0x01, // data_reference_index
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // reserved
      track.channelCount,
      0x00, 0x10, // sampleSize
      0x00, 0x00, // pre_defined
      0x00, 0x00, // reserved
      (track.sampleRate >> 8) & 0xff,
      track.sampleRate & 0xff, // sampleRate
      0x00, 0x00
    ])

    const opusSpecificConfig = track.config.length ? MP4.dOps(track) : []
    return MP4.box(MP4.types.Opus, opusAudioDescription, opusSpecificConfig)
  }
https://opus-codec.org/docs/opus_in_isobmff.html