A NOTE has been added to this issue. ====================================================================== <https://bugtrack.alsa-project.org/alsa-bug/view.php?id=2238> ====================================================================== Reported By: Raymond Assigned To: ====================================================================== Project: ALSA - lib Issue ID: 2238 Category: 1_pcm - digital audio Reproducibility: always Severity: minor Priority: normal Status: new ====================================================================== Date Submitted: 06-28-2006 09:53 CEST Last Modified: 06-30-2006 07:10 CEST ====================================================================== Summary: snd_pcm_hw_params() did not return error Description: If alsa-lib require the application to refine hw_params from those values supported by alsa-driver to a set of unique values Why do snd_pcm_hw_params() did not return error in the following code ? Does it mean that snd_pcm_hw_params_set_period_size() or snd_pcm_hw_params_set_buffer_size() is not necessary for some ALSA driver ? #include <alsa/asoundlib.h> int main() { snd_pcm_t* pcm; snd_pcm_hw_params_t* hwparams; int err; unsigned int rate = 44100; unsigned int channels = 2; int dir = 0; if ( snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0) < 0 ) printf("Cannot open pcm.\n"); else { printf("pcm state after pcm open : %d\n",snd_pcm_state(pcm)); snd_pcm_hw_params_alloca(&hwparams); snd_pcm_hw_params_any(pcm, hwparams); snd_pcm_hw_params_set_access(pcm, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED); snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE); snd_pcm_hw_params_set_channels (pcm, hwparams, channels); snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, &dir); printf("pcm state before hw_params : %d\n",snd_pcm_state(pcm)); err = snd_pcm_hw_params(pcm, hwparams) ; if ( err < 0 ) printf("Error setting hw params: %s.\n", snd_strerror(err)); printf("pcm state after hw_params : %d\n",snd_pcm_state(pcm)); snd_pcm_close(pcm); } } ====================================================================== ---------------------------------------------------------------------- rlrevell - 06-30-06 05:22 ---------------------------------------------------------------------- If you don't set the period size, the default is driver and configuration dependent. Applications cannot rely on the default period size being sane. ---------------------------------------------------------------------- Raymond - 06-30-06 07:10 ---------------------------------------------------------------------- The application are required to select period size and buffer size from possibe set of values. In general, is there any difference if the application set period_size first or set buffer_size first ? #include <alsa/asoundlib.h> int main() { snd_pcm_t* pcm; snd_pcm_hw_params_t* hwparams; snd_pcm_uframes_t size,size_min,size_max,buf_size,buf_size_min,buf_size_max; int err; unsigned int rate = 44100; unsigned int channels = 2; int dir = 0; if ( snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0) < 0 ) printf("Cannot open pcm.\n"); else { printf("pcm state after pcm open : %d\n",snd_pcm_state(pcm)); snd_pcm_hw_params_alloca(&hwparams); snd_pcm_hw_params_any(pcm, hwparams); err = snd_pcm_hw_params_set_access(pcm, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED); if ( err < 0 ) printf("Error set access : %s\n",snd_strerror(err)); err = snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE); if ( err < 0 ) printf("Error set format : %s\n",snd_strerror(err)); err = snd_pcm_hw_params_set_channels (pcm, hwparams, channels); if ( err < 0 ) printf("Error set channels : %s\n",snd_strerror(err)); err = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, &dir); if ( err < 0 ) printf("Error set rate near : %s\n",snd_strerror(err)); /* print possible period size */ err = snd_pcm_hw_params_get_period_size_min(hwparams, &size_min, &dir); if (err < 0) printf("Unable to get period size min for playback: %s\n", snd_strerror(err)); err = snd_pcm_hw_params_get_period_size_max(hwparams, &size_max, &dir); if (err < 0) printf("Unable to get period size max for playback: %s\n", snd_strerror(err)); printf("period size (min =%d max = %d)\n",size_min,size_max); for (size=size_min; size<=size_max; size++) if ( snd_pcm_hw_params_test_period_size(pcm,hwparams,size,dir) == 0 ) printf(" %d\n",size); /* print possible buffer size */ err = snd_pcm_hw_params_get_buffer_size_min(hwparams, &buf_size_min); if (err < 0) printf("Unable to get buffer size min for playback: %s\n", snd_strerror(err)); err = snd_pcm_hw_params_get_buffer_size_max(hwparams, &buf_size_max); if (err < 0) printf("Unable to get buffer size max for playback: %s\n", snd_strerror(err)); printf("buffer size (min =%d max = %d)\n",buf_size_min,buf_size_max); for (buf_size=buf_size_min; buf_size<=buf_size_max; buf_size++) if ( snd_pcm_hw_params_test_buffer_size(pcm,hwparams,buf_size) == 0 ) printf(" %d\n",buf_size); printf("pcm state before hw_params : %d\n",snd_pcm_state(pcm)); err = snd_pcm_hw_params(pcm, hwparams) ; if ( err < 0 ) printf("Error setting hw params: %s\n", snd_strerror(err)); printf("pcm state after hw_params : %d\n",snd_pcm_state(pcm)); err = snd_pcm_hw_params_get_period_size(hwparams, &size, &dir); if (err < 0) printf("Unable to get period size for playback: %s\n", snd_strerror(err)); else printf("period size = %d\n",size); err = snd_pcm_hw_params_get_buffer_size(hwparams, &buf_size); if (err < 0) printf("Unable to get buffer size for playback: %s\n", snd_strerror(err)); else printf("buffer size = %d\n",buf_size); snd_pcm_close(pcm); } } Issue History Date Modified Username Field Change ====================================================================== 06-28-06 09:53 Raymond New Issue 06-30-06 04:53 Raymond Note Added: 0010717 06-30-06 05:22 rlrevell Note Added: 0010718 06-30-06 07:10 Raymond Note Added: 0010719 ====================================================================== Using Tomcat but need to do more? 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