Hi All, Say hello to everyone! I'm a new member to learn how to write a ALSA application. I analyze the source code of aplay and very confused on follow interfaces: snd_pcm_playback_info() snd_pcm_playback_format() snd_pcm_playback_params() The aplay is belongs to alsa-utils that also is a application. It should be use interfaces of alsa-lib, but why i can't find these interfaces in alsa-lib ? Could you tell me where can find out these interface? Looking forward to your reply! Best regards Spring