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kaklik |
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <poll.h>
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kaklik |
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#include <alsa/asoundlib.h>
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kaklik |
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snd_pcm_t *playback_handle;
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short buf[4096];
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int
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playback_callback (snd_pcm_sframes_t nframes)
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{
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int err;
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printf ("playback callback called with %u frames\n", nframes);
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/* ... fill buf with data ... */
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if ((err = snd_pcm_writei (playback_handle, buf, nframes)) < 0) {
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fprintf (stderr, "write failed (%s)\n", snd_strerror (err));
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}
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return err;
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}
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main (int argc, char *argv[])
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{
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snd_pcm_hw_params_t *hw_params;
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snd_pcm_sw_params_t *sw_params;
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snd_pcm_sframes_t frames_to_deliver;
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int nfds;
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int err;
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struct pollfd *pfds;
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if ((err = snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
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fprintf (stderr, "cannot open audio device %s (%s)\n",
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argv[1],
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
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fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
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fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
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fprintf (stderr, "cannot set access type (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
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fprintf (stderr, "cannot set sample format (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0)) < 0) {
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fprintf (stderr, "cannot set sample rate (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2)) < 0) {
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fprintf (stderr, "cannot set channel count (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) {
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fprintf (stderr, "cannot set parameters (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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snd_pcm_hw_params_free (hw_params);
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/* tell ALSA to wake us up whenever 4096 or more frames
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of playback data can be delivered. Also, tell
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ALSA that we'll start the device ourselves.
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*/
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if ((err = snd_pcm_sw_params_malloc (&sw_params)) < 0) {
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fprintf (stderr, "cannot allocate software parameters structure (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_sw_params_current (playback_handle, sw_params)) < 0) {
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fprintf (stderr, "cannot initialize software parameters structure (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096)) < 0) {
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fprintf (stderr, "cannot set minimum available count (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 0U)) < 0) {
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fprintf (stderr, "cannot set start mode (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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if ((err = snd_pcm_sw_params (playback_handle, sw_params)) < 0) {
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fprintf (stderr, "cannot set software parameters (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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/* the interface will interrupt the kernel every 4096 frames, and ALSA
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will wake up this program very soon after that.
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*/
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if ((err = snd_pcm_prepare (playback_handle)) < 0) {
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fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
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snd_strerror (err));
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exit (1);
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}
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while (1) {
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/* wait till the interface is ready for data, or 1 second
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has elapsed.
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*/
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if ((err = snd_pcm_wait (playback_handle, 1000)) < 0) {
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fprintf (stderr, "poll failed (%s)\n", strerror (errno));
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break;
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}
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/* find out how much space is available for playback data */
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if ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) < 0) {
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if (frames_to_deliver == -EPIPE) {
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fprintf (stderr, "an xrun occured\n");
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break;
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} else {
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fprintf (stderr, "unknown ALSA avail update return value (%d)\n",
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frames_to_deliver);
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break;
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}
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}
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frames_to_deliver = frames_to_deliver > 4096 ? 4096 : frames_to_deliver;
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/* deliver the data */
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if (playback_callback (frames_to_deliver) != frames_to_deliver) {
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fprintf (stderr, "playback callback failed\n");
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break;
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}
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}
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snd_pcm_close (playback_handle);
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exit (0);
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}
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