• attachment:pcm_minimal.c of KansaiDebianMeeting/20131027

   1 /*
   2  * pcm_minimal.c - simple noise generator as ALSA application
   3  * Copyright (c) 2006 Jaroslav Kysela <perex@perex.cz>
   4  *               2013 Takashi Sakamoto <o-takashi@sakamocchi.jp>
   5  *
   6  * This application is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU Lesser General Public License as
   8  * published by the Free Software Foundation; either version 2.1 of
   9  * the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  19  *
  20  * NOTE: this application is based on /test/pcm_min.c in alsa-lib package.
  21  */
  22 
  23 /*
  24  * In debian, 'libasound2-dev' package includes this header
  25  */
  26 #include <alsa/asoundlib.h>
  27 
  28 /*
  29  * compile:
  30  * $ gcc ./pcm_minimal.c -lasound -o ./noise
  31  */
  32 
  33 /* playback PCM node */
  34 static char *device = "default";
  35 
  36 /* random samples */
  37 unsigned char buffer[16 * 1024] = {0};
  38 
  39 int main(void)
  40 {
  41 	unsigned int i;
  42 	snd_pcm_t *handle;
  43 	snd_pcm_hw_params_t *hw_params;
  44 	snd_pcm_sframes_t frames;
  45 
  46 	/* generate noise samples */
  47 	for (i = 0; i < sizeof(buffer); i++)
  48 		buffer[i] = random() & 0xff;
  49 
  50 	/* open with blocking mode */
  51 	snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0);
  52 
  53 	/* set hardware parameters */
  54 	snd_pcm_hw_params_malloc(&hw_params);
  55 	snd_pcm_hw_params_any(handle, hw_params);
  56 	snd_pcm_hw_params_set_format(handle, hw_params, SND_PCM_FORMAT_U8);
  57 	snd_pcm_hw_params_set_access(handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
  58 	snd_pcm_hw_params_set_channels(handle, hw_params, 1);
  59 	snd_pcm_hw_params_set_rate(handle, hw_params, 48000, 0);
  60 	snd_pcm_hw_params(handle, hw_params);
  61 	snd_pcm_hw_params_free(hw_params);
  62 
  63 	/* write samples into buffer */
  64 	for (i = 0; i < 20; i++) {
  65 		frames = snd_pcm_writei(handle, buffer, sizeof(buffer));
  66 		if (frames < 0)
  67 			frames = snd_pcm_recover(handle, frames, 0);
  68 		if (frames < 0) {
  69 			; /* cannot resolve XRUN */
  70 		}
  71 		if (frames > 0 && frames < (long)sizeof(buffer)) {
  72 			; /* cannot write all of samples */
  73 		}
  74 	}
  75 
  76 	snd_pcm_drain(handle);
  77 	snd_pcm_close(handle);
  78 	return 0;
  79 }