alsa_a.c

MIDI解码程序(用VC编写)

  total_bytes = frag_size * frags;
  ctl->cmsg(CMSG_INFO, VERB_VERBOSE,
	    "Requested buffer size %d, fragment size %d",
	    total_bytes, frag_size);
  if ((tmp = snd_pcm_hw_params_set_buffer_size_near(handle, pinfo, total_bytes >> sample_shift)) < 0) {
    ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
	      "ALSA pcm '%s' can't set buffer size %d",
	      alsa_device_name(), total_bytes);
    snd_pcm_close(handle);
    return -1;
  }

  if ((tmp = snd_pcm_hw_params_set_period_size_near(handle, pinfo, frag_size >> sample_shift, 0)) < 0) {
    ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
	      "ALSA pcm '%s' can't set period size %d",
	      alsa_device_name(), frag_size);
    snd_pcm_close(handle);
    return -1;
  }

  if (snd_pcm_hw_params(handle, pinfo) < 0) {
    snd_output_t *log;
    ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
	      "ALSA pcm '%s' can't set hw_params", alsa_device_name());
    snd_output_stdio_attach(&log, stderr, 0);
    snd_pcm_hw_params_dump(pinfo, log);
    snd_pcm_close(handle);
    return -1;
  }

  total_bytes = snd_pcm_hw_params_get_buffer_size(pinfo) << sample_shift;
  frag_size = snd_pcm_hw_params_get_period_size(pinfo, NULL) << sample_shift;
  ctl->cmsg(CMSG_INFO, VERB_VERBOSE,
	    "ALSA pcm '%s' set buffer size %d, period size %d bytes",
	    alsa_device_name(), total_bytes, frag_size);
  tmp = snd_pcm_hw_params_get_rate(pinfo, NULL);
  if (tmp > 0 && tmp != dpm.rate) {
    dpm.rate = tmp;
    ret_val = 1;
  }
  if (orig_rate != dpm.rate) {
    ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
	      "Output rate adjusted to %d Hz (requested %d Hz)",
	      dpm.rate, orig_rate);
  }
  snd_pcm_sw_params_current(handle, swpinfo);
  snd_pcm_sw_params_set_start_threshold(handle, swpinfo, total_bytes >> sample_shift);
  snd_pcm_sw_params_set_stop_threshold(handle, swpinfo, total_bytes >> sample_shift);

  tmp = snd_pcm_prepare(handle);
  if (tmp < 0) {
    ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
	      "unable to prepare channel\n");
    snd_pcm_close(handle);
    return -1;
  }

  pfds = snd_pcm_poll_descriptors_count(handle);
  if (pfds > 1) {
    ctl->cmsg(CMSG_ERROR, VERB_NORMAL, "too many poll descriptors: %s",
	      alsa_device_name());
    close_output ();
    return -1;
  } else if (pfds == 1) {
    struct pollfd pfd;
    if (snd_pcm_poll_descriptors(handle, &pfd, 1) >= 0)
      dpm.fd = pfd.fd;
    else
      dpm.fd = -1;
  } else
    dpm.fd = -1;

  output_counter = 0;

  return ret_val;
}

static void close_output(void)
{
  if (handle) {
    int ret = snd_pcm_close (handle);
    if (ret < 0)
      error_report (ret);
    handle = NULL;
  }

  dpm.fd = -1;
}

static int output_data(char *buf, int32 nbytes)
{
  int n;
  int nframes, shift;

  if (! handle)
    return -1;

  nframes = nbytes;
  shift = 0;
  if (!(dpm.encoding & PE_MONO))
    shift++;
  if (dpm.encoding & PE_16BIT)
    shift++;
  nframes >>= shift;
  
  while (nframes > 0) {
    n = snd_pcm_writei(handle, buf, nframes);
    if (n == -EAGAIN || (n >= 0 && n < nframes)) {
      snd_pcm_wait(handle, 1000);
    } else if (n == -EPIPE) {
      snd_pcm_status_t *status;
      snd_pcm_status_alloca(&status);
      if (snd_pcm_status(handle, status) < 0) {
	ctl->cmsg(CMSG_WARNING, VERB_DEBUG, "%s: cannot get status", alsa_device_name());
	return -1;
      }
      ctl->cmsg(CMSG_INFO, VERB_DEBUG,
		"%s: underrun at %ld", alsa_device_name(), output_counter << sample_shift);
      snd_pcm_prepare(handle);
    } else if (n < 0) {
      ctl->cmsg(CMSG_WARNING, VERB_DEBUG,
		"%s: %s", alsa_device_name(),
		(n < 0) ? snd_strerror(n) : "write error");
      return -1;
    }
    if (n > 0) {
      nframes -= n;
      buf += n << shift;
      output_counter += n;
    }
  }

  return 0;
}

static int acntl(int request, void *arg)
{
  snd_pcm_status_t *status;
  snd_pcm_sframes_t delay;

  if (handle == NULL)
    return -1;

  switch (request) {
  case PM_REQ_GETFRAGSIZ:
    if (frag_size == 0)
      return -1;
    *((int *)arg) = frag_size;
    return 0;

  case PM_REQ_GETQSIZ:
    if (total_bytes == -1)
      return -1;
    *((int *)arg) = total_bytes;
    return 0;

  case PM_REQ_GETFILLABLE:
    if (total_bytes == -1)
      return -1;
    snd_pcm_status_alloca(&status);
    if (snd_pcm_status(handle, status) < 0)
      return -1;
    *((int *)arg) = snd_pcm_status_get_avail(status);
    return 0;
    
  case PM_REQ_GETFILLED:
    if (total_bytes == -1)
      return -1;
    if (snd_pcm_delay(handle, &delay) < 0)
      return -1;
    *((int *)arg) = delay;
    return 0;

  case PM_REQ_GETSAMPLES:
    if (total_bytes == -1)
      return -1;
    if (snd_pcm_delay(handle, &delay) < 0)
      return -1;
    *((int *)arg) = output_counter - delay;
    return 0;

  case PM_REQ_DISCARD:
    if (snd_pcm_drop(handle) < 0)
      return -1;
    if (snd_pcm_prepare(handle) < 0)
      return -1;
    output_counter = 0;
    return 0;

  case PM_REQ_FLUSH:
    if (snd_pcm_drain(handle) < 0)
      return -1;
    if (snd_pcm_prepare(handle) < 0)
      return -1;
    output_counter = 0;
    return 0;
  }
  return -1;
}


/* end ALSA API 0.9.x */


#elif ALSA_LIB == 5

/*================================================================
 * ALSA API version 0.5.x
 *================================================================*/

/*return value == 0 sucess
               == 1 warning
               == -1 fails
 */
static int set_playback_info (snd_pcm_t* handle__,
			      int32* encoding__, int32* rate__,
			      const int32 extra_param[5])
{
  int ret_val = 0;
  const int32 orig_rate = *rate__;
  int tmp;
  snd_pcm_channel_info_t   pinfo;
  snd_pcm_channel_params_t pparams;
  snd_pcm_channel_setup_t  psetup;

  memset (&pinfo, 0, sizeof (pinfo));
  memset (&pparams, 0, sizeof (pparams));
  pinfo.channel = SND_PCM_CHANNEL_PLAYBACK;
  tmp = snd_pcm_channel_info (handle__, &pinfo);
  if (tmp < 0)
    {
      error_report (tmp);
      return -1;
    }

  /*check sample bit*/
  if (!(pinfo.formats & ~(SND_PCM_FMT_S8 | SND_PCM_FMT_U8)))
    *encoding__ &= ~PE_16BIT; /*force 8bit samples*/
  if (!(pinfo.formats & ~(SND_PCM_FMT_S16 | SND_PCM_FMT_U16)))
    *encoding__ |= PE_16BIT; /*force 16bit samples*/

  /*check rate*/
  if (pinfo.min_rate > *rate__)
    *rate__ = pinfo.min_rate;
  if (pinfo.max_rate < *rate__)
    *rate__ = pinfo.max_rate;
  pparams.format.rate = *rate__;

  /*check channels*/
  if ((*encoding__ & PE_MONO) != 0 && pinfo.min_voices > 1)
    *encoding__ &= ~PE_MONO;
  if ((*encoding__ & PE_MONO) == 0 && pinfo.max_voices < 2)
    *encoding__ |= PE_MONO;

  if ((*encoding__ & PE_MONO) != 0)
    pparams.format.voices = 1; /*mono*/
  else
    pparams.format.voices = 2; /*stereo*/

  /*check format*/
  if ((*encoding__ & PE_16BIT) != 0)
    { /*16bit*/
      if ((pinfo.formats & SND_PCM_FMT_S16_LE) != 0)
	{
	  pparams.format.format = SND_PCM_SFMT_S16_LE;
	  *encoding__ |= PE_SIGNED;
	}
      else if ((pinfo.formats & SND_PCM_FMT_U16_LE) != 0)
	{
	  pparams.format.format = SND_PCM_SFMT_U16_LE;
	  *encoding__ &= ~PE_SIGNED;
	}
      else if ((pinfo.formats & SND_PCM_FMT_S16_BE) != 0)
	{
	  pparams.format.format = SND_PCM_SFMT_S16_BE;
	  *encoding__ |= PE_SIGNED;
	}
      else if ((pinfo.formats & SND_PCM_FMT_U16_BE) != 0)
	{
	  pparams.format.format = SND_PCM_SFMT_U16_BE;
	  *encoding__ &= ~PE_SIGNED;
	}
      else
	{
	  ctl->cmsg(CMSG_ERROR, VERB_NORMAL,
		    "%s doesn't support 16 bit sample width",
		    alsa_device_name());
	  return -1;
	}
    }
  else
    { /*8bit*/
      if ((pinfo.formats & SND_PCM_FMT_U8) != 0)
	{
	  pparams.format.format = SND_PCM_SFMT_U8;
	  *encoding__ &= ~PE_SIGNED;
	}
#if 0
      else if ((pinfo.formats & SND_PCM_FMT_S8) != 0)
	{
	  pcm_format.format = SND_PCM_SFMT_U16_LE;
	  *encoding__ |= PE_SIGNED;
	}
#endif
      else
	{
	  ctl->cmsg(CMSG_ERROR, VERB_NORMAL,
		    "%s doesn't support 8 bit sample width",
		    alsa_device_name());
	  return -1;
	}
    }


  sample_shift = 0;
  if (!(dpm.encoding & PE_MONO))
    sample_shift++;
  if (dpm.encoding & PE_16BIT)
    sample_shift++;

  /* Set buffer fragment size (in extra_param[1]) */
  if (extra_param[1] != 0)
    tmp = extra_param[1];
  else
    tmp = audio_buffer_size << sample_shift;

  /* Set buffer fragments (in extra_param[0]) */
  pparams.buf.block.frag_size = tmp;
  pparams.buf.block.frags_max = (extra_param[0] == 0) ? -1 : extra_param[0];
  pparams.buf.block.frags_min = 1;
  pparams.mode = SND_PCM_MODE_BLOCK;
  pparams.channel = SND_PCM_CHANNEL_PLAYBACK;
  pparams.start_mode = SND_PCM_START_DATA; /* .. should be START_FULL */
  pparams.stop_mode  = SND_PCM_STOP_STOP;
  pparams.format.interleave = 1;
  snd_pcm_channel_flush (handle__, SND_PCM_CHANNEL_PLAYBACK);
  tmp = snd_pcm_channel_params (handle__, &pparams);
  if (tmp < 0)
    {
      ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
		"%s doesn't support buffer fragments"
		":request size=%d, max=%d, min=%d\n",
		alsa_device_name(),
		pparams.buf.block.frag_size,
		pparams.buf.block.frags_max,
		pparams.buf.block.frags_min);
      return -1;
    }

  tmp = snd_pcm_channel_prepare (handle__, SND_PCM_CHANNEL_PLAYBACK);
  if (tmp < 0)
    {
      ctl->cmsg(CMSG_WARNING, VERB_NORMAL,
		"unable to prepare channel\n");
      return -1;
    }

  memset (&psetup, 0, sizeof(psetup));
  psetup.channel = SND_PCM_CHANNEL_PLAYBACK;
  tmp = snd_pcm_channel_setup (handle__, &psetup);
  if (tmp == 0)
    {
      if(psetup.format.rate != orig_rate)
        {
	  ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		    "Output rate adjusted to %d Hz (requested %d Hz)",
		    psetup.format.rate, orig_rate);
	  dpm.rate = psetup.format.rate;
	  ret_val = 1;
	}
      frag_size = psetup.buf.block.frag_size;
      total_bytes = frag_size * psetup.buf.block.frags;
    }
  else
    {
      frag_size = 0;
      total_bytes = -1; /* snd_pcm_playback_status fails */
    }

  return ret_val;
}


static int detect(void)
{
  snd_pcm_t *pcm;
  if (snd_pcm_open(&pcm, card, device, SND_PCM_OPEN_PLAYBACK | SND_PCM_OPEN_NONBLOCK) < 0)
    return 0;
  snd_pcm_close(pcm);
  return 1; /* found */
}

static int open_output(void)
{
  int tmp, warnings=0;
  int ret;

  tmp = check_sound_cards (&card, &device, dpm.extra_param);
  if (tmp < 0)
    return -1;

  /* Open the audio device */
  ret = snd_pcm_open (&handle, card, device, SND_PCM_OPEN_PLAYBACK | SND_PCM_OPEN_NONBLOCK);
  if (ret < 0)
    {
      ctl->cmsg(CMSG_ERROR, VERB_NORMAL, "%s: %s",
		alsa_device_name(), snd_strerror (ret));
      return -1;
    }

  snd_pcm_nonblock_mode(handle, 0); /* set back to blocking mode */
  /* They can't mean these */
  dpm.encoding &= ~(PE_ULAW|PE_ALAW|PE_BYTESWAP);
  warnings = set_playback_info (handle, &dpm.encoding, &dpm.rate,
				dpm.extra_param);
  if (warnings < 0)
    {
      close_output ();
      return -1;
    }

  dpm.fd = snd_pcm_file_descriptor (handle, SND_PCM_CHANNEL_PLAYBACK);
  output_counter = 0;
  return warnings;
}

static void close_output(void)
{
  int ret;

  if (handle == NULL)
    return;