text: import Box from '../box'
  Box.btrt = function (data, output) {
    const stream = this.stream
    stream.writeUint32(this.bufferSizeDB)
    stream.writeUint32(this.maxBitrate)
    stream.writeUint32(this.avgBitrate)
    output.write(new Uint8Array(stream.buffer.slice(0, stream.position)))
    if (stream.position !== data.size - 8) {
      throw new Error(`${data.type} box incomplete`)
    } else {
      this.outputSize = stream.position
    }
    delete this.data
  }
  