From mboxrd@z Thu Jan  1 00:00:00 1970
From: Enno Fennema <ennofennema@tele2.nl>
Subject: Re: snd_pcm_wait function (really snd_pcm_draiin)
Date: Fri, 16 Nov 2012 17:27:07 +0100
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To: Daniel Sanz <daniellsanz2@gmail.com>
Cc: alsa-devel@alsa-project.org, Trent Piepho <tpiepho@gmail.com>, Clemens Ladisch <clemens@ladisch.de>
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On 11/16/12 11:41, Daniel Sanz wrote:
> Thanks, Trent, I've been playing a bit with snd_pcm_drain,
> snd_pcm_writei, blocking mode, non-blocking mode, etc. but even if I
> ...

I wanted to play a short sound and release the pcm. It works with a 
non-block drain as Clemens suggested.

I noticed using gettimeofday() around drain() that it takes a bit over 2 
seconds. Rather long for a sound that only takes 0.1 sec.
Not draining aand a usleep() for 0.1 sec plays the full time and 
releases the cpm quicker. As you see in attached example I don't bother 
with periods either.

Not exactly your question but I have given up on drainage for my current 
application.

Regards,
Enno Fennema

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#include <alsa/asoundlib.h>
#include <math.h>

int main(int argc, char** argv) {
  int err, i, n;
  snd_pcm_t *handle;
  int16_t buffer[500];

  for( i = 0; i < 500; i++ ) {		// put 500 samples in buffer
    double omega = (double)(i % 50) * 2.0 * M_PI / 50;
    buffer[i] = sin(omega) * 2500;
  }
  snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
  snd_pcm_set_params(handle, SND_PCM_FORMAT_S16, 
		     SND_PCM_ACCESS_RW_INTERLEAVED, 
		     1, 22000, 0, 50000 );
  snd_pcm_start(handle);

  n = 2200;		
  while( n > 500 ) {
    err = snd_pcm_writei(handle, buffer, 500);
    if( err < 0 )
      printf("Error %d : %s\n", err, snd_strerror(err));
    n -= err;
  }
  err = snd_pcm_writei(handle, buffer, n);

#if 0
  snd_pcm_nonblock(handle, 0);	// ** 1 - nonblock; 0 - Do block
  snd_pcm_drain(handle);
#else
  usleep(100000);
#endif
  return 0;
}

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