Re: [alsa-devel] capturing data from the microphone

Hi,

I have the same kind of problem. I try to capture PCM stream thanks to areacord : # arecord -c 1 -t wav -f S16_LE -r 8000 -d 10 input.wav

30 seconds later I have the folowing message : # arecord: pcm_read:1629: read error: Input/output error

I can observe the PCM stream on an oscilloscope but no interrupt are catched by the system (AIC ss0 counter remains at zero ) : # cat /proc/interrupts CPU0 1: 275059 AIC at91_tick, rtc0, ttyS0 7: 179 AIC ttyS2 9: 11 AIC mmc0 13: 0 AIC atmel_spi.1 14: 0 AIC ssc0 82: 1 GPIO alerte 107: 9464 GPIO eth0

Any idea?

Riccardo Magliocchetti wrote:

[the same message is waiting in moderator queue, sorry if you receive it two times]

Hello,

i'm trying to capture audio data from the microphone, but i'm not able to read any frames. The frames are always 0 and delay is fixed to 2730. I've tried calling snd_pcm_avail_delay, snd_pcm_avail_update but does not make a difference. The soundcard is driven by snd_hda_intel. The code is more or less the same as Paul Davis' tutorial on using the alsa api.

This is the code for init and the loop that tries to read the data:

#define MIC_BUFSIZE 4096

static gpointer snd_pcm_read(gpointer data) { int error; snd_pcm_sframes_t frames = MIC_BUFSIZE;

while (TRUE) {

 if ((error = snd_pcm_wait (pcm_handle, 1000)) < 0) {
     g_printerr("Failed to poll: %s\n", snd_strerror(error));
     continue;
 }

 if ((error = snd_pcm_avail(pcm_handle)) < 0) {
   if (error == -EPIPE) {
     g_printerr("xrun! %s\n", snd_strerror(error));
     continue;
     //return GINT_TO_POINTER(FALSE);
   } else {
     g_printerr("alsa_pcm_avail_update error %s\n", snd_strerror(error));
     continue;
     //return GINT_TO_POINTER(FALSE);
   }
 }

 frames = error;
 if (frames == 0)
   continue;

 frames = frames > MIC_BUFSIZE ? MIC_BUFSIZE : frames;
 g_printerr ("frames: %ld\n", frames);
 g_static_mutex_lock(&mutex);
 error = snd_pcm_readi(pcm_handle, Mic_Buffer[Mic_WriteBuf], frames);
 g_static_mutex_unlock(&mutex);
 if (error < 0)
     error = snd_pcm_recover(pcm_handle, error, 0);
 if (error < 0) {
    LOG("snd_pcm_readi FAIL!: %s\n", snd_strerror(error));
 }

}

return GINT_TO_POINTER(TRUE); }

BOOL Mic_Init() { snd_pcm_hw_params_t *hwparams; snd_pcm_sw_params_t *swparams; int err;

 if (Mic_Inited)
     return TRUE;

 // Open the default sound card in capture
 if ((err = snd_pcm_open(&pcm_handle, "default", SND_PCM_STREAM_CAPTURE,

/*SND_PCM_NONBLOCK*/ 0)) < 0) { g_printerr("Failed to open device: %s\n", snd_strerror(err)); return FALSE; }

 // Allocate the snd_pcm_hw_params_t structure and fill it.
 snd_pcm_hw_params_alloca(&hwparams);
 if ((err = snd_pcm_hw_params_any(pcm_handle, hwparams)) < 0) {
     g_printerr("Failed to setup hw parameters: %s\n", snd_strerror(err));
     return FALSE;
 }

 //Set the access
 if ((err = snd_pcm_hw_params_set_access(pcm_handle, hwparams,

SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) { g_printerr("Failed to set access: %s\n", snd_strerror(err)); return FALSE; }

 //dir 0 == exacte (Rate = 16K exacte)
 if ((err = snd_pcm_hw_params_set_rate(pcm_handle, hwparams, 16000, 0)) < 0) {
     g_printerr("Failed to set rate: %s\n", snd_strerror(err));
     return FALSE;
 }

 /* Set sample format */
 if ((err = snd_pcm_hw_params_set_format(pcm_handle, hwparams, SND_PCM_FORMAT_S8)) < 0) {
     g_printerr("Failed to set format: %s\n", snd_strerror(err));
     return FALSE;
 }

 // Set one channel (mono)
 if ((err = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, 1)) < 0) {
     g_printerr("Failed to set channels: %s\n", snd_strerror(err));
     return FALSE;
 }

 //Set the params
 if ((err = snd_pcm_hw_params(pcm_handle, hwparams)) < 0) {
     g_printerr("Failed to set hw parameters: %s\n", snd_strerror(err));
     return FALSE;
 }

 snd_pcm_sw_params_alloca(&swparams);
 if ((err = snd_pcm_sw_params_current (pcm_handle, swparams)) < 0) {
     g_printerr("Failed to set current sw parameters: %s\n", snd_strerror(err));
     return FALSE;
 }

 if ((err = snd_pcm_sw_params_set_avail_min (pcm_handle, swparams, MIC_BUFSIZE)) < 0) {
     g_printerr("Failed to set minimum available count: %s\n", snd_strerror(err));
     return FALSE;
 }

 if ((err = snd_pcm_sw_params_set_start_threshold (pcm_handle, swparams, 0U)) < 0) {
     g_printerr("Failed to set start mode: %s\n", snd_strerror(err));
     return FALSE;
 }

 if ((err = snd_pcm_sw_params (pcm_handle, swparams)) < 0) {
     g_printerr("Failed to set sw parameters: %s\n", snd_strerror(err));
     return FALSE;
 }

 if ((err = snd_pcm_prepare (pcm_handle)) < 0) {
     g_printerr("Failed to prepare audio interface to use: %s\n", snd_strerror(err));
     return FALSE;
 }

 Mic_Inited = TRUE;
 Mic_Reset();

 mic_reader = g_thread_create(snd_pcm_read, NULL, TRUE, NULL);

 return TRUE;

}

thanks, Riccardo

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