C++ snd_pcm_drain函数代码示例

/* close the audio device */
int ao_plugin_close(ao_device *device)
{
	ao_alsa_internal *internal;

	if (device) {
          if ((internal = (ao_alsa_internal *) device->internal)) {
            if (internal->pcm_handle) {

              /* this is a PulseAudio ALSA emulation bug workaround;
                 snd_pcm_drain always takes about 2 seconds, even if
                 there's nothing to drain.  Rather than wait for no
                 reason, determine the current playback depth, wait
                 that long, then kill the stream.  Remove this code
                 once Pulse gets fixed. */

              snd_pcm_sframes_t sframes;
              if(snd_pcm_delay (internal->pcm_handle, &sframes)){
                snd_pcm_drain(internal->pcm_handle);
              }else{
                double s = (double)(sframes - internal->static_delay)/internal->sample_rate;
                if(s>1){
                  /* something went wrong; fall back */
                  snd_pcm_drain(internal->pcm_handle);
                }else{
                  if(s>0){
                    struct timespec sleep,wake;
                    sleep.tv_sec = (int)s;
                    sleep.tv_nsec = (s-sleep.tv_sec)*1000000000;
                    while(nanosleep(&sleep,&wake)<0){
                      if(errno==EINTR)
                        sleep=wake;
                      else
                        break;
                    }
                  }
                }
              }
              snd_pcm_close(internal->pcm_handle);
              if(internal->local_config)
                snd_config_delete(internal->local_config);
              internal->local_config=NULL;
              internal->pcm_handle=NULL;
            }
          } else
            awarn("ao_plugin_close called with uninitialized ao_device->internal\n");
	} else
          awarn("ao_plugin_close called with uninitialized ao_device\n");

	return 1;
}

void Audio::run()
{
    if (!initialized)
    {
        init();
        initialized = true;
        qDebug() << "Audio components initialized.";
    }

    if (synth->masterPlaying && synth->isPlaying())
    {
        replaceBuffer(synth->genChunk());
        playBuffer();
//        resetBuffer();
    }

    if (state != snd_pcm_state(handle))
    {
        state = snd_pcm_state(handle);
        qDebug() << "State: " << state;
    }

    // Buffer underrun (not being written to fast enough)
    if (state == 4)
    {
        snd_pcm_drain(handle);
        prepareDevice();
    }
}

static void stop(void) {
    if (alsa_handle) {
        snd_pcm_drain(alsa_handle);
        snd_pcm_close(alsa_handle);
        alsa_handle = NULL;
    }
}

int
sa_stream_drain(sa_stream_t *s)
{
  if (s == NULL || s->output_unit == NULL) {
    return SA_ERROR_NO_INIT;
  }

  if (snd_pcm_state(s->output_unit) == SND_PCM_STATE_PREPARED) {
    size_t min_samples = 0;
    size_t min_bytes = 0;
    void *buf;

    if (sa_stream_get_min_write(s, &min_samples) < 0)
      return SA_ERROR_SYSTEM;
    min_bytes = snd_pcm_frames_to_bytes(s->output_unit, min_samples);    

    buf = malloc(min_bytes);
    if (!buf)
      return SA_ERROR_SYSTEM;
    memset(buf, 0, min_bytes);
    sa_stream_write(s, buf, min_bytes);
    free(buf);
  }

  if (snd_pcm_state(s->output_unit) != SND_PCM_STATE_RUNNING) {
    return SA_ERROR_INVALID;
  }
  snd_pcm_drain(s->output_unit);
  return SA_SUCCESS;
}

 static void alsaCleanup(Soloud *aSoloud)
 {
     if (0 == aSoloud->mBackendData)
     {
         return;
     }
     ALSAData *data = static_cast<ALSAData*>(aSoloud->mBackendData);
     data->audioProcessingDone = true;
     if (data->threadHandle)
     {
         Thread::wait(data->threadHandle);
         Thread::release(data->threadHandle);
     }
     snd_pcm_drain(data->alsaDeviceHandle);
     snd_pcm_close(data->alsaDeviceHandle);
     if (0 != data->sampleBuffer)
     {
         delete[] data->sampleBuffer;
     }
     if (0 != data->buffer)
     {
         delete[] data->buffer;
     }
     delete data;
     aSoloud->mBackendData = 0;
 }

static int alsa_can_read(snd_pcm_t *dev)
{
	snd_pcm_sframes_t avail;
	int err;

	alsa_resume(dev);
	avail = snd_pcm_avail_update(dev);
	/* A buggy driver does not return an error while being in Xrun */
	if (avail >= 0 && snd_pcm_state(dev) == SND_PCM_STATE_XRUN) avail=-EPIPE;
	if (avail < 0) {
		ms_error("snd_pcm_avail_update: %s", snd_strerror(avail));	// most probably -EPIPE
		/* overrun occured, snd_pcm_state() would return SND_PCM_STATE_XRUN
		 FIXME: handle other error conditions*/
		ms_error("*** alsa_can_read fixup, trying to recover");
		snd_pcm_drain(dev); /* Ignore possible error, at least -EAGAIN.*/
		err = snd_pcm_recover(dev, avail, 0);
		if (err){
			ms_error("snd_pcm_recover() failed with err %d: %s", err, snd_strerror(err));
			return -1;
		}
		err = snd_pcm_start(dev);
		if (err){
			ms_error("snd_pcm_start() failed with err %d: %s", err, snd_strerror(err));
			return -1;
		}
		ms_message("Recovery done");
	}
	return avail;
}

// 释放资源
void sound_info_free(struct SoundInfo *info) {
    
    snd_pcm_drain(info->handle);
    snd_pcm_close(info->handle);
    free(info->buffer);
    free(info);
}

 int main(int argc, char *argv[]) 
 { 
     char *filename; 
     char *devicename = "default"; 
     int fd; 
     WAVContainer_t wav; 
     SNDPCMContainer_t playback; 
      
     if (argc != 2) { 
         fprintf(stderr, "Usage: ./lplay <file name>/n"); 
         return -1; 
     } 
      
     memset(&playback, 0x0, sizeof(playback)); 
  
     filename = argv[1]; 
     fd = open(filename, O_RDONLY); 
     if (fd < 0) { 
         fprintf(stderr, "Error open [%s]/n", filename); 
         return -1; 
     } 
      
     if (WAV_ReadHeader(fd, &wav) < 0) { 
         fprintf(stderr, "Error WAV_Parse [%s]/n", filename); 
         goto Err; 
     } 
  
     if (snd_output_stdio_attach(&playback.log, stderr, 0) < 0) {
         fprintf(stderr, "Error snd_output_stdio_attach/n"); 
         goto Err; 
     } 
  
     if (snd_pcm_open(&playback.handle, devicename, SND_PCM_STREAM_PLAYBACK, 0) < 0) { 
         fprintf(stderr, "Error snd_pcm_open [ %s]/n", devicename); 
         goto Err; 
     } 
  
     if (SNDWAV_SetParams(&playback, &wav) < 0) { 
         fprintf(stderr, "Error set_snd_pcm_params/n"); 
         goto Err; 
     } 
     snd_pcm_dump(playback.handle, playback.log); 
  
     SNDWAV_Play(&playback, &wav, fd); 
  
     snd_pcm_drain(playback.handle); 
  
     close(fd); 
     free(playback.data_buf); 
     snd_output_close(playback.log); 
     snd_pcm_close(playback.handle); 
     return 0; 
  
 Err: 
     close(fd); 
     if (playback.data_buf) free(playback.data_buf); 
     if (playback.log) snd_output_close(playback.log); 
     if (playback.handle) snd_pcm_close(playback.handle); 
     return -1; 
 } 

void Mouth::close(){
    snd_pcm_hw_params_free(params);
    snd_pcm_drain(capture_handle);
    snd_pcm_close(capture_handle);
    snd_config_update_free_global();
    open=false;
}

bool SoundProcessor::Record(){
  SetUpRecorder();
  snd_pcm_sframes_t fwdframes=snd_pcm_forwardable(handle_m);
  printf("forwarding %d\n",fwdframes);
  snd_pcm_forward(handle_m,fwdframes);
  while (true) {
    rc_m = snd_pcm_readi(handle_m, buffer_m, frames);
    if (rc_m == -EPIPE) {
      /* EPIPE means overrun */
      fprintf(stderr, "overrun occurred\n");
      snd_pcm_prepare(handle_m);
    } else if (rc_m < 0) {
      fprintf(stderr,
              "error from read: %s\n",
              snd_strerror(rc_m));
    } else if (rc_m != (int)frames) {
      fprintf(stderr, "short read, read %d frames\n", rc_m);
    }
    rc_m = write(1, buffer_m, size);
    if (rc_m != size)
      fprintf(stderr,
              "short write: wrote %d bytes\n", rc_m);
  }

  snd_pcm_drain(handle_m);
  snd_pcm_close(handle_m);
  free(buffer_m);
  return true;
}

/*----------------------------------------------------------------------
|    AlsaOutput_Close
+---------------------------------------------------------------------*/
static BLT_Result
AlsaOutput_Close(AlsaOutput* self)
{
    ATX_LOG_FINER("closing output");

    switch (self->state) {
      case BLT_ALSA_OUTPUT_STATE_CLOSED:
        /* ignore */
        return BLT_SUCCESS;

      case BLT_ALSA_OUTPUT_STATE_PREPARED:
        /* wait for buffers to finish */
        ATX_LOG_FINER("snd_pcm_drain");
        snd_pcm_drain(self->device_handle);
        /* FALLTHROUGH */

      case BLT_ALSA_OUTPUT_STATE_OPEN:
      case BLT_ALSA_OUTPUT_STATE_CONFIGURED:
        /* close the device */
        ATX_LOG_FINER("snd_pcm_close");
        snd_pcm_close(self->device_handle);
        self->device_handle = NULL;
        break;
    }

    /* update the state */
    AlsaOutput_SetState(self, BLT_ALSA_OUTPUT_STATE_CLOSED);

    return BLT_SUCCESS;
}

void alsa_close(alsa_dev_t *alsa_dev)
{
    snd_pcm_drain(alsa_dev->snd_pcm);
    snd_pcm_close(alsa_dev->snd_pcm);

    free(alsa_dev);
}

static void
alsa_close( void )
{
	snd_pcm_drain( alsa.pcm );
	snd_pcm_close( alsa.pcm );
	alsa.pcm = NULL;
}

void close_alsa(struct pcm *pcm)
{
	struct alsa *alsa = (struct alsa *)(pcm->data);
	snd_pcm_drain(alsa->pcm);
	snd_pcm_close(alsa->pcm);
	free(alsa);
}

void
ags_devout_alsa_free(AgsDevout *devout)
{
  snd_pcm_drain(devout->out.alsa.handle);
  snd_pcm_close(devout->out.alsa.handle);
  devout->out.alsa.handle = NULL;
}