2，Error恢复

分析Error Code，根据error Code做不同的处理

3，PCM STATE具体介绍

SND_PCM_STATE_OPEN

The PCM device is in the open state. After the snd_pcm_open() open call, the device is in this state. Also, when snd_pcm_hw_params() call fails, then this state is entered to force application calling snd_pcm_hw_params() function to set right communication parameters.

SND_PCM_STATE_SETUP

The PCM device has accepted communication parameters and it is waiting for snd_pcm_prepare() call to prepare the hardware for selected operation (playback or capture).

SND_PCM_STATE_PREPARED

The PCM device is prepared for operation. Application can use snd_pcm_start() call, write or read data to start the operation.

SND_PCM_STATE_RUNNING

The PCM device has been started and is running. It processes the samples. The stream can be stopped using the snd_pcm_drop() or snd_pcm_drain() calls.

SND_PCM_STATE_XRUN

The PCM device reached overrun (capture) or underrun (playback). You can use the -EPIPE return code from I/O functions ( snd_pcm_writei() , snd_pcm_writen() , snd_pcm_readi() , snd_pcm_readn() ) to determine this state without checking the actual state via snd_pcm_state() call. It is recommended to use the helper function snd_pcm_recover() to recover from this state, but you can also use snd_pcm_prepare() , snd_pcm_drop() or snd_pcm_drain() calls.

SND_PCM_STATE_DRAINING

The device is in this state when application using the capture mode called snd_pcm_drain() function. Until all data are read from the internal ring buffer using I/O routines ( snd_pcm_readi() , snd_pcm_readn() ), then the device stays in this state.

SND_PCM_STATE_PAUSED

The device is in this state when application called the snd_pcm_pause() function until the pause is released. Not all hardware supports this feature. Application should check the capability with the snd_pcm_hw_params_can_pause() .

SND_PCM_STATE_SUSPENDED

The device is in the suspend state provoked with the power management system. The stream can be resumed using snd_pcm_resume() call, but not all hardware supports this feature. Application should check the capability with the snd_pcm_hw_params_can_resume() . In other case, the calls snd_pcm_prepare() , snd_pcm_drop() , snd_pcm_drain() can be used to leave this state.

SND_PCM_STATE_DISCONNECTED

The device is physicaly disconnected. It does not accept any I/O calls in this state.

4，PCM State值