What may cause audio capture stop in alsa for linux?

Thanks,we will try that.

hi Pavel,

I want to known if the"XRUN status" is relate to Linux kernel ,could the function "snd_pcm_prepare" recovery alsa to normal;
and if Linux kernel cause alsa STOP, when I am to readi audio data,could it return error or Blocked(can't return anything)

I ask this two question because we use alsa function snd_pcm_readi to read audio data and if it return error,we will use snd_pcm_prepare ,but in this case we also encounter “XRUN”,and all the function stop working.

this is our record code(init & read):

Int audioCaptureInit(pAudio hdl) {
	int err;
	snd_pcm_hw_params_t * hw_params = NULL;

	if (hdl == NULL) {
		return -1;
	}
	if ((err = snd_pcm_open(&hdl->m_audcap_hdl, ALSA_CAPTURE_DEVICE, SND_PCM_STREAM_CAPTURE, 0)) < 0) {
        fprintf (stderr, "AUDIO >>  cannot open audio device %s (%s)\n", ALSA_CAPTURE_DEVICE, snd_strerror (err));
        return  -1;
	}

	if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
		return  -1;
	}

	if ((err = snd_pcm_hw_params_any(hdl->m_audcap_hdl, hw_params)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
		return -1;
	}

	if ((err = snd_pcm_hw_params_set_access(hdl->m_audcap_hdl, hw_params,SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	}

	if ((err = snd_pcm_hw_params_set_format(hdl->m_audcap_hdl, hw_params,SND_PCM_FORMAT_S16_LE)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}

	if ((err = snd_pcm_hw_params_set_rate_near(hdl->m_audcap_hdl, hw_params,&(hdl->audioParames.sampleRate), 0)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}

	if ((err = snd_pcm_hw_params_set_channels(hdl->m_audcap_hdl, hw_params,hdl->audioParames.channelNums)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}

	if ((err = snd_pcm_hw_params_set_buffer_size(hdl->m_audcap_hdl, hw_params, AUDIO_CAPTURE_BUFFER_SIZE)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}

#if 1
	int dir;
	snd_pcm_uframes_t size;
	static snd_pcm_sframes_t buffer_size;
	static snd_pcm_sframes_t period_size = AUDIO_MAX_IN_FRAMES;

	/* set the period size */
	err = snd_pcm_hw_params_set_period_size_near(hdl->m_audcap_hdl, hw_params, &period_size, 0);
	if (err < 0) {
		printf("Unable to set period size %d for playback: %s\n", period_size, snd_strerror(err));
		return err;
	}

	err = snd_pcm_hw_params_get_period_size(hw_params, &size, &dir);
	if (err < 0) {
		printf("Unable to get period size for capture: %s\n", snd_strerror(err));
		return err;
	}
	period_size = size;
    OSA_printf("=======================period size====%d====================\n:",size);
#endif

	if ((err = snd_pcm_hw_params(hdl->m_audcap_hdl, hw_params)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}
	snd_pcm_hw_params_free(hw_params);
	if ((err = snd_pcm_prepare(hdl->m_audcap_hdl)) < 0) {
		fprintf(stderr,"AUDIO >> audcap_device_init: %s (%s)\n",hdl->m_audcap_hdl,snd_strerror (err));
	    return -1;
	}
	return 0;
}

Int audioRecord(pAudio hdl, void *buf, Int32 *numFrames) {
	//return 0 on succeeding
	int err;
	Int status = 0;

	err = snd_pcm_readi(hdl->m_audcap_hdl, buf, *numFrames);
	if (err < 0 || err != *numFrames) {
		OSA_printf("audio_record: err=%d, Reason: %s\n",err, snd_strerror(err));
		if (strcmp(snd_strerror(err), "Success")) {
			OSA_printf("++++++++++++++++FAILED+++++++++++++++++ %s\n");
		}
                status = 1;
		snd_pcm_prepare(hdl->m_audcap_hdl);	
	}
	return status;
}

look forward to your reply,thanks!

Dongmei,

dongmei ma said:

I want to known if the"XRUN status" is relate to Linux kernel

Can you provide me the exact console output/log when you get this "XRUN status" reported?

dongmei ma said:

could the function "snd_pcm_prepare" recovery alsa to normal

ALSA documents states that this function should be called to recover ALSA capture to normal:

SND_PCM_STATE_XRUN

The PCM device reached overrun (capture) or underrun (playback). You can use the -EPIPE return code from I/O functions (snd_pcm_writei(), snd_pcm_writen(), snd_pcm_readi(), snd_pcm_readn()) to determine this state without checking the actual state via snd_pcm_state() call. It is recommended to use the helper function snd_pcm_recover() to recover from this state, but you can also use snd_pcm_prepare(), snd_pcm_drop() or snd_pcm_drain() calls.

 

 

 

 

 

3. PCM capture

See also if the below wiki pages will be in help:

 

 

BR
Pavel

hi Pavel,
Thanks for your reply,the problem we encountered is sporadic,we don't know when it will XRUN,and we don't known what will cause XRUN,and so we can't get any log information.
we will try to replace Linux kernel firstly,and test it ,thanks