AlexxIT/go2rtc · error

alsa: can't convert to

Error message

alsa: can't convert %s to %s

What it means

Guard in Playback.AddTrack: no PCM transcode handler exists for converting the incoming track codec to the codec the sound card negotiated (rate/channels near the source). The unsupported source codec is at fault.

Solutions

1. Send a codec supported by the playback path (PCM) or one with a known converter
2. Update the transcode codec table to support this source codec

When it happens

Trigger: Thrown at pkg/alsa/playback_linux.go:60 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of AlexxIT/go2rtc@c245815e75 (2026-09-07). Data as JSON: /api/errors/49d1f302326930cf. Report an issue: GitHub.

Appendix: source

Thrown at pkg/alsa/playback_linux.go:60

}

func (p *Playback) AddTrack(media *core.Media, codec *core.Codec, track *core.Receiver) error {
	src := track.Codec
	dst := &core.Codec{
		Name:      core.CodecPCML,
		ClockRate: p.dev.GetRateNear(src.ClockRate),
		Channels:  p.dev.GetChannelsNear(src.Channels),
	}
	sender := core.NewSender(media, dst)

	sender.Handler = func(pkt *rtp.Packet) {
		if n, err := p.dev.Write(pkt.Payload); err == nil {
			p.Send += n
		}
	}

	if sender.Handler = pcm.TranscodeHandler(dst, src, sender.Handler); sender.Handler == nil {
		return fmt.Errorf("alsa: can't convert %s to %s", src, dst)
	}

	// typical card support:
	// - Formats: S16_LE, S32_LE
	// - ClockRates: 8000 - 192000
	// - Channels: 2 - 10
	err := p.dev.SetHWParams(device.SNDRV_PCM_FORMAT_S16_LE, dst.ClockRate, byte(dst.Channels))
	if err != nil {
		return err
	}

	sender.HandleRTP(track)
	p.Senders = append(p.Senders, sender)
	return nil
}

func (p *Playback) Start() (err error) {
	return p.closed.Wait()

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