code: func (self AudioFrame) Concat(in AudioFrame) (out AudioFrame) {
  	out = self
  	out.Data = append([][]byte(nil), out.Data...)
  	out.SampleCount += in.SampleCount
  	for i := range out.Data {
  		out.Data[i] = append(out.Data[i], in.Data[i]...)
  	}
  	return
  }
docs: // Concat two audio frames.