Method AudioDecode

backend/go/opus/opus.go:126–184

(req *pb.AudioDecodeRequest)

}

func (o *Opus) AudioDecode(req *pb.AudioDecodeRequest) (*pb.AudioDecodeResult, error) {
	if len(req.Frames) == 0 {
		return &pb.AudioDecodeResult{
			SampleRate:      opusSampleRate,
			SamplesPerFrame: opusFrameSize,
		}, nil
	}

	// Use a persistent decoder when a session ID is provided so that Opus
	// prediction state carries across batches. Fall back to a fresh decoder
	// for backward compatibility.
	sessionID := req.Options["session_id"]

	var cd *cachedDecoder
	var ownedDec *Decoder

	if sessionID != "" && o.decoders != nil {
		var err error
		cd, err = o.getOrCreateDecoder(sessionID)
		if err != nil {
			return nil, fmt.Errorf("opus decoder create: %w", err)
		}
		cd.mu.Lock()
		defer cd.mu.Unlock()
	} else {
		dec, err := NewDecoder(opusSampleRate, opusChannels)
		if err != nil {
			return nil, fmt.Errorf("opus decoder create: %w", err)
		}
		ownedDec = dec
		defer ownedDec.Close()
	}

	dec := ownedDec
	if cd != nil {
		dec = cd.dec
	}

	var allSamples []int16
	var samplesPerFrame int32

	pcm := make([]int16, opusMaxFrameSize)
	for _, frame := range req.Frames {
		n, err := dec.Decode(frame, pcm, opusMaxFrameSize, false)
		if err != nil {
			return nil, fmt.Errorf("opus decode: %w", err)
		}
		if samplesPerFrame == 0 {
			samplesPerFrame = int32(n)
		}
		allSamples = append(allSamples, pcm[:n]...)
	}

	return &pb.AudioDecodeResult{
		PcmData:         sound.Int16toBytesLE(allSamples),
		SampleRate:      opusSampleRate,
		SamplesPerFrame: samplesPerFrame,
	}, nil