code: func (d *Decoder) Format() *audio.Format {
  	if d == nil {
  		return nil
  	}
  	return &audio.Format{
  		NumChannels: int(d.NumChans),
  		SampleRate:  int(d.SampleRate),
  		BitDepth:    int(d.BitDepth),
  		Endianness:  binary.BigEndian,
  	}
  }
docs: // Format returns the audio format of the decoded content.