ao_alsa.c

自己移植的linux下的流媒体播放器原代码,支持mms协议,支持ftp和http协议.

    }
}

/* stop playing and empty buffers (for seeking/pause) */
static void reset()
{
    int err;

    if ((err = snd_pcm_drop(alsa_handler)) < 0)
    {
	mp_msg(MSGT_AO,MSGL_ERR,"alsa-reset: pcm drop error: %s\n", snd_strerror(err));
	return;
    }
    if ((err = snd_pcm_prepare(alsa_handler)) < 0)
    {
	mp_msg(MSGT_AO,MSGL_ERR,"alsa-reset: pcm prepare error: %s\n", snd_strerror(err));
	return;
    }
    return;
}

#ifdef USE_POLL
static int wait_for_poll(snd_pcm_t *handle, struct pollfd *ufds, unsigned int count)
{
  unsigned short revents;

  while (1) {
    poll(ufds, count, -1);
    snd_pcm_poll_descriptors_revents(handle, ufds, count, &revents);
    if (revents & POLLERR)
      return -EIO;
    if (revents & POLLOUT)
      return 0;
  }
} 
#endif

#ifndef timersub
#define timersub(a, b, result) \
do { \
	(result)->tv_sec = (a)->tv_sec - (b)->tv_sec; \
  (result)->tv_usec = (a)->tv_usec - (b)->tv_usec; \
  if ((result)->tv_usec < 0) { \
		--(result)->tv_sec; \
		(result)->tv_usec += 1000000; \
	} \
} while (0)
#endif

/* I/O error handler */
static int xrun(u_char *str_mode)
{
  int err;
  snd_pcm_status_t *status;

  snd_pcm_status_alloca(&status);
  
  if ((err = snd_pcm_status(alsa_handler, status))<0) {
    mp_msg(MSGT_AO,MSGL_ERR,"status error: %s", snd_strerror(err));
    return(0);
  }

  if (snd_pcm_status_get_state(status) == SND_PCM_STATE_XRUN) {
    struct timeval now, diff, tstamp;
    gettimeofday(&now, 0);
    snd_pcm_status_get_trigger_tstamp(status, &tstamp);
    timersub(&now, &tstamp, &diff);
    mp_msg(MSGT_AO,MSGL_INFO,"alsa-%s: xrun of at least %.3f msecs. resetting stream\n",
	   str_mode,
	   diff.tv_sec * 1000 + diff.tv_usec / 1000.0);
  }

  if ((err = snd_pcm_prepare(alsa_handler))<0) {
    mp_msg(MSGT_AO,MSGL_ERR,"xrun: prepare error: %s", snd_strerror(err));
    return(0);
  }

  return(1); /* ok, data should be accepted again */
}

static int play_normal(void* data, int len);
static int play_mmap(void* data, int len);

static int play(void* data, int len, int flags)
{
  int result;
  if (ao_mmap)
    result = play_mmap(data, len);
  else
    result = play_normal(data, len);

  return result;
}

/*
    plays 'len' bytes of 'data'
    returns: number of bytes played
    modified last at 29.06.02 by jp
    thanxs for marius <[e-mail]> for giving us the light ;)
*/

static int play_normal(void* data, int len)
{

  //bytes_per_sample is always 4 for 2 chn S16_LE
  int num_frames = len / bytes_per_sample;
  char *output_samples = (char *)data;
  snd_pcm_sframes_t res = 0;

  //mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: frames=%i, len=%i\n",num_frames,len);

  if (!alsa_handler) {
    mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: device configuration error");
    return 0;
  }

  while (num_frames > 0) {

    res = snd_pcm_writei(alsa_handler, (void *)output_samples, num_frames);

      if (res == -EAGAIN) {
	snd_pcm_wait(alsa_handler, 1000);
      }
      else if (res == -EPIPE) {  /* underrun */
	if (xrun("play") <= 0) {
	  mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: xrun reset error");
	  return(0);
	}
      }
      else if (res == -ESTRPIPE) {	/* suspend */
	mp_msg(MSGT_AO,MSGL_INFO,"alsa-play: pcm in suspend mode. trying to resume\n");
	while ((res = snd_pcm_resume(alsa_handler)) == -EAGAIN)
	  sleep(1);
      }
      else if (res < 0) {
	mp_msg(MSGT_AO,MSGL_INFO,"alsa-play: unknown status, trying to reset soundcard\n");
	if ((res = snd_pcm_prepare(alsa_handler)) < 0) {
	   mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: snd prepare error");
	  return(0);
	  break;
	}
      }

      if (res > 0) {

	/* output_samples += ao_data.channels * res; */
	output_samples += res * bytes_per_sample;

	num_frames -= res;
      }

  } //end while

  if (res < 0) {
    mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: write error %s", snd_strerror(res));
    return 0;
  }
  return len - len % bytes_per_sample;
}

/* mmap-mode mainly based on descriptions by Joshua Haberman <[e-mail]>
 * 'An overview of the ALSA API' http://people.debian.org/~joshua/x66.html
 * and some help by Paul Davis <[e-mail]> */

static int play_mmap(void* data, int len)
{
  snd_pcm_sframes_t commitres, frames_available;
  snd_pcm_uframes_t frames_transmit, size, offset;
  const snd_pcm_channel_area_t *area;
  void *outbuffer;
  int result;

#ifdef USE_POLL //seems not really be needed
  struct pollfd *ufds;
  int count;

  count = snd_pcm_poll_descriptors_count (alsa_handler);
  ufds = malloc(sizeof(struct pollfd) * count);
  snd_pcm_poll_descriptors(alsa_handler, ufds, count);

  //first wait_for_poll
    if (err = (wait_for_poll(alsa_handler, ufds, count) < 0)) {
      if (snd_pcm_state(alsa_handler) == SND_PCM_STATE_XRUN || 
	  snd_pcm_state(alsa_handler) == SND_PCM_STATE_SUSPENDED) {
        xrun("play");
      }
    }
#endif

  outbuffer = alloca(ao_data.buffersize);

  //don't trust get_space() ;)
  frames_available = snd_pcm_avail_update(alsa_handler) * bytes_per_sample;
  if (frames_available < 0)
    xrun("play");

  if (frames_available < 4) {
    if (first) {
      first = 0;
      snd_pcm_start(alsa_handler);
    }
    else { //FIXME should break and return 0?
      snd_pcm_wait(alsa_handler, -1);
      first = 1;
    }
  }

  /* len is simply the available bufferspace got by get_space() 
   * but real avail_buffer in frames is ab/bytes_per_sample */
  size = len / bytes_per_sample;

  //mp_msg(MSGT_AO,MSGL_V,"len: %i size %i, f_avail %i, bps %i ...\n", len, size, frames_available, bytes_per_sample);

  frames_transmit = size;

  /* prepare areas and set sw-pointers
   * frames_transmit returns the real available buffer-size
   * sometimes != frames_available cause of ringbuffer 'emulation' */
  snd_pcm_mmap_begin(alsa_handler, &area, &offset, &frames_transmit);

  /* this is specific to interleaved streams (or non-interleaved
   * streams with only one channel) */
  outbuffer = ((char *) area->addr + (area->first + area->step * offset) / 8); //8

  //write data
  memcpy(outbuffer, data, (frames_transmit * bytes_per_sample));

  commitres = snd_pcm_mmap_commit(alsa_handler, offset, frames_transmit);

  if (commitres < 0 || commitres != frames_transmit) {
    if (snd_pcm_state(alsa_handler) == SND_PCM_STATE_XRUN || 
	snd_pcm_state(alsa_handler) == SND_PCM_STATE_SUSPENDED) {
      xrun("play");
    }
  }

  //mp_msg(MSGT_AO,MSGL_V,"mmap ft: %i, cres: %i\n", frames_transmit, commitres);

  /* 	err = snd_pcm_area_copy(&area, offset, &data, offset, len, alsa_format); */
  /* 	if (err < 0) { */
  /* 	  mp_msg(MSGT_AO,MSGL_ERR,"area-copy-error\n"); */
  /* 	  return 0; */
  /* 	} */


  //calculate written frames!
  result = commitres * bytes_per_sample;


  /* if (verbose) { */
  /* if (len == result) */
  /* mp_msg(MSGT_AO,MSGL_V,"result: %i, frames written: %i ...\n", result, frames_transmit); */
  /* else */
  /* mp_msg(MSGT_AO,MSGL_V,"result: %i, frames written: %i, result != len ...\n", result, frames_transmit); */
  /* } */

  //mplayer doesn't like -result
  if (result < 0)
    result = 0;

#ifdef USE_POLL
  free(ufds);
#endif

  return result;
}

/* how many byes are free in the buffer */
static int get_space()
{
    snd_pcm_status_t *status;
    int ret;
    char *str_status;

    //snd_pcm_sframes_t avail_frames = 0;
    
    snd_pcm_status_alloca(&status);
    
    if ((ret = snd_pcm_status(alsa_handler, status)) < 0)
    {
	mp_msg(MSGT_AO,MSGL_ERR,"alsa-space: cannot get pcm status: %s\n", snd_strerror(ret));
	return(0);
    }
    
    switch(snd_pcm_status_get_state(status))
    {
    case SND_PCM_STATE_OPEN:
      str_status = "open";
      ret = snd_pcm_status_get_avail(status) * bytes_per_sample;
      break;
    case SND_PCM_STATE_PREPARED:
	str_status = "prepared";
	first = 1;
	ret = snd_pcm_status_get_avail(status) * bytes_per_sample;
	if (ret == 0) //ugly workaround for hang in mmap-mode
	  ret = 10;
	break;
    case SND_PCM_STATE_RUNNING:
      ret = snd_pcm_status_get_avail(status) * bytes_per_sample;
      //avail_frames = snd_pcm_avail_update(alsa_handler) * bytes_per_sample;
      if (str_status != "open" && str_status != "prepared")
	str_status = "running";
      break;
    case SND_PCM_STATE_PAUSED:
      mp_msg(MSGT_AO,MSGL_V,"alsa-space: paused");
      str_status = "paused";
      ret = 0;
      break;
    case SND_PCM_STATE_XRUN:
      xrun("space");
      str_status = "xrun";
      first = 1;
      ret = 0;
      break;
    default:
      str_status = "undefined";
      ret = snd_pcm_status_get_avail(status) * bytes_per_sample;
      if (ret <= 0) {
	xrun("space");
      }
    }

    if (snd_pcm_status_get_state(status) != SND_PCM_STATE_RUNNING)
      mp_msg(MSGT_AO,MSGL_V,"alsa-space: free space = %i, %s --\n", ret, str_status);
    
    if (ret < 0) {
      mp_msg(MSGT_AO,MSGL_ERR,"negative value!!\n");
      ret = 0;
    }
 
    // workaround for too small value returned
    if (ret < MIN_CHUNK_SIZE)
      ret = 0;

    return(ret);
}

/* delay in seconds between first and last sample in buffer */
static float get_delay()
{

  if (alsa_handler) {

    snd_pcm_status_t *status;
    float ret;
    
    snd_pcm_status_alloca(&status);
    
    if ((ret = snd_pcm_status(alsa_handler, status)) < 0)
    {
	mp_msg(MSGT_AO,MSGL_ERR,"alsa-delay: cannot get pcm status: %s\n", snd_strerror(ret));
    }
    
    switch(snd_pcm_status_get_state(status))
    {
	case SND_PCM_STATE_OPEN:
	case SND_PCM_STATE_PREPARED:
	case SND_PCM_STATE_RUNNING:
	    ret = (float)snd_pcm_status_get_delay(status)/(float)ao_data.samplerate;
	    break;
	default:
	    ret = 0;
    }
    

    if (ret < 0)
      ret = 0;
    return(ret);
    
  } else {
    return(0);
  }
}