snd_pcm_access_name((snd_pcm_access_t)val)); } printf("\nPCM formats:\n"); for (val =0; val<= SND_PCM_FORMAT_LAST; val++) { if (snd_pcm_format_name((snd_pcm_format_t)val)!= NULL) { printf(" %s (%s)\n", snd_pcm_format_name((snd_pcm_format_t)val), snd_pcm_forma...
snd_pcm_uframes_t frames; /* Open PCM device for playback. */ rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0); if (rc < 0) { fprintf(stderr, "unable to open pcm device: %s\n", snd_strerror(rc)); exit(1); } /* Allocate a hardware parameters object. ...
snd_pcm_open是Alsa库提供的打开设备调用函数,这里我们指定打开缺省的音频设备,并根据参数mode将设备置为录音或是播放状态,如果设备打开成功,pcm_handle便指向该设备句柄,我们用全局变量保存起来,方便以后使用。 第二步是设置参数,参数设置不当将会导致音频设备无法正常工作。在设置参数前,我们需要了解一下各个参数的含...
1, open, 这个和 oss 相同,对应于 alsa 就是 snd_pcm_open ; 2, param 设置,这个就是 snd_pcm_hw_params; 3, 上层的 alsa 在设置 param 的成功以后或者出错的时候恢复都需要调用 snd_pcm_prepare; 4, write 函数; 现在一个个的来看; 4.1.1 open 过程介绍 如下图所示: 就是我先前说的分成三部分,...
==> snd_pcm_open_conf(pcmp, name, root, conf, stream, mode); ==> open_func = snd_dlobj_cache_lookup(open_name);将获得lib库中_snd_pcm_empty_open函数 所以open_func将等于_snd_pcm_empty_open _snd_pcm_empty_open _snd_pcm_asym_open _snd_pcm_plug_open _snd_pcm_softvol_open _snd...
==> snd_pcm_playback_open或者snd_pcm_capture_open ==> snd_pcm_open或者oss的snd_pcm_oss_f_reg.snd_pcm_oss_open,这就对应/dev/dsp了 ==> snd_pcm_open_file或者oss的snd_pcm_oss_open_file ==> snd_pcm_open_substream ==> soc_pcm_open ...
printf("PCM stream types:\n"); for (val = 0; val <= SND_PCM_STREAM_LAST; val++) { printf(" %s\n", snd_pcm_stream_name((snd_pcm_stream_t)val)); } printf("PCM access types:\n"); for (val = 0; val <= SND_PCM_ACCESS_LAST; val++) { ...
我在Ubuntu 16.04主机上运行Ubuntu 12.04Docker容器。我在一些测试代码中使用SND_PCM_STREAM_PLAYBACK和SND_PCM_STREAM_CAPTURE流类型练习了'snd_pcm_open'/'snd_pcm_close‘操作。我不需要任何实际的声音/音频功能,但只需使用有效的句柄获取'snd_pcm_open‘返回0,然后在同一句柄上使用 ...
snd_pcm_f_ops[2] ==> snd_pcm_playback_open或者snd_pcm_capture_open ==> snd_pcm_open或者oss的snd_pcm_oss_f_reg.snd_pcm_oss_open,这就对应/dev/dsp了 ==> snd_pcm_open_file或者oss的snd_pcm_oss_open_file ==> snd_pcm_open_substream ...
snd_pcm_open()和 snd_pcm_close()仅一次（应用程序的开始和结束）并在您要重置流时使用此选项：snd...