| 0,0 → 1,165 |
|---|
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <errno.h> |
| #include <poll.h> |
| #include <alsa/asoundlib.h> |
| |
| snd_pcm_t *playback_handle; |
| short buf[4096]; |
| |
| int |
| playback_callback (snd_pcm_sframes_t nframes) |
| { |
| int err; |
| |
| printf ("playback callback called with %u frames\n", nframes); |
| |
| /* ... fill buf with data ... */ |
| |
| if ((err = snd_pcm_writei (playback_handle, buf, nframes)) < 0) { |
| fprintf (stderr, "write failed (%s)\n", snd_strerror (err)); |
| } |
| |
| return err; |
| } |
| |
| main (int argc, char *argv[]) |
| { |
| |
| snd_pcm_hw_params_t *hw_params; |
| snd_pcm_sw_params_t *sw_params; |
| snd_pcm_sframes_t frames_to_deliver; |
| int nfds; |
| int err; |
| struct pollfd *pfds; |
| |
| if ((err = snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0)) < 0) { |
| fprintf (stderr, "cannot open audio device %s (%s)\n", |
| argv[1], |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) { |
| fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) { |
| fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) { |
| fprintf (stderr, "cannot set access type (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) { |
| fprintf (stderr, "cannot set sample format (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0)) < 0) { |
| fprintf (stderr, "cannot set sample rate (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2)) < 0) { |
| fprintf (stderr, "cannot set channel count (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) { |
| fprintf (stderr, "cannot set parameters (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| snd_pcm_hw_params_free (hw_params); |
| |
| /* tell ALSA to wake us up whenever 4096 or more frames |
| of playback data can be delivered. Also, tell |
| ALSA that we'll start the device ourselves. |
| */ |
| |
| if ((err = snd_pcm_sw_params_malloc (&sw_params)) < 0) { |
| fprintf (stderr, "cannot allocate software parameters structure (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| if ((err = snd_pcm_sw_params_current (playback_handle, sw_params)) < 0) { |
| fprintf (stderr, "cannot initialize software parameters structure (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| if ((err = snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096)) < 0) { |
| fprintf (stderr, "cannot set minimum available count (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| if ((err = snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 0U)) < 0) { |
| fprintf (stderr, "cannot set start mode (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| if ((err = snd_pcm_sw_params (playback_handle, sw_params)) < 0) { |
| fprintf (stderr, "cannot set software parameters (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| /* the interface will interrupt the kernel every 4096 frames, and ALSA |
| will wake up this program very soon after that. |
| */ |
| |
| if ((err = snd_pcm_prepare (playback_handle)) < 0) { |
| fprintf (stderr, "cannot prepare audio interface for use (%s)\n", |
| snd_strerror (err)); |
| exit (1); |
| } |
| |
| while (1) { |
| |
| /* wait till the interface is ready for data, or 1 second |
| has elapsed. |
| */ |
| |
| if ((err = snd_pcm_wait (playback_handle, 1000)) < 0) { |
| fprintf (stderr, "poll failed (%s)\n", strerror (errno)); |
| break; |
| } |
| |
| /* find out how much space is available for playback data */ |
| |
| if ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) < 0) { |
| if (frames_to_deliver == -EPIPE) { |
| fprintf (stderr, "an xrun occured\n"); |
| break; |
| } else { |
| fprintf (stderr, "unknown ALSA avail update return value (%d)\n", |
| frames_to_deliver); |
| break; |
| } |
| } |
| |
| frames_to_deliver = frames_to_deliver > 4096 ? 4096 : frames_to_deliver; |
| |
| /* deliver the data */ |
| |
| if (playback_callback (frames_to_deliver) != frames_to_deliver) { |
| fprintf (stderr, "playback callback failed\n"); |
| break; |
| } |
| } |
| |
| snd_pcm_close (playback_handle); |
| exit (0); |
| } |
| |