AlexxIT/go2rtc · error

[alsa] set hw_params

Error message

[alsa] set hw_params: %w

What it means

The SNDRV_PCM_IOCTL_HW_PARAMS ioctl failed while applying hardware parameters (format, rate, channels, buffer size) to the ALSA PCM device. Wraps the errno from the kernel; common causes are unsupported sample format/rate/channel count for the device or the device being in an incompatible state. Called by Start and AddTrack.

Solutions

1. Request a different sample format, rate, or channel count supported by the device
2. Free other streams using the same PCM device and retry
3. Check dmesg for ALSA driver details on why params were rejected

When it happens

Trigger: Thrown at pkg/alsa/device/device_linux.go:135 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/8fb80eda95d12115. Report an issue: GitHub.

Appendix: source

Thrown at pkg/alsa/device/device_linux.go:135

		return c2
	}
	return channels
}

const bufferSize = 4096

func (d *Device) SetHWParams(format byte, rate uint32, channels byte) error {
	d.setInterval(SNDRV_PCM_HW_PARAM_CHANNELS, uint32(channels))
	d.setInterval(SNDRV_PCM_HW_PARAM_RATE, rate)
	d.setMask(SNDRV_PCM_HW_PARAM_FORMAT, uint32(format))
	//d.setMask(SNDRV_PCM_HW_PARAM_SUBFORMAT, 0)

	// important for smooth playback
	d.setInterval(SNDRV_PCM_HW_PARAM_BUFFER_SIZE, bufferSize)
	//d.setInterval(SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2000)

	if err := ioctl(d.fd, SNDRV_PCM_IOCTL_HW_PARAMS, &d.hwparams); err != nil {
		return fmt.Errorf("[alsa] set hw_params: %w", err)
	}

	_, i := d.getInterval(SNDRV_PCM_HW_PARAM_FRAME_BITS)
	d.frameBytes = int(i / 8)

	_, periods := d.getInterval(SNDRV_PCM_HW_PARAM_PERIODS)
	_, periodSize := d.getInterval(SNDRV_PCM_HW_PARAM_PERIOD_SIZE)
	threshold := snd_pcm_uframes_t(periods * periodSize) // same as bufferSize

	swparams := snd_pcm_sw_params{
		//tstamp_mode: SNDRV_PCM_TSTAMP_ENABLE,
		period_step:    1,
		avail_min:      1, // start as soon as possible
		stop_threshold: threshold,
	}

	if d.IsCapture() {
		swparams.start_threshold = 1

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