Subversion Repositories svnkaklik

        #include <stdio.h>
        #include <stdlib.h>
        #include <errno.h>
        #include <poll.h>
        #include &ltalsa/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);
        }