C++ snd_pcm_hw_params_get_buffer_size函数代码示例

/**************************************************************************
 * 				wodUpdatePlayedTotal	[internal]
 *
 */
static BOOL wodUpdatePlayedTotal(WINE_WAVEDEV* wwo, snd_pcm_status_t* ps)
{
    snd_pcm_sframes_t delay;
    snd_pcm_sframes_t avail;
    snd_pcm_uframes_t buf_size = 0;
    snd_pcm_state_t state;

    state = snd_pcm_state(wwo->pcm);
    avail = snd_pcm_avail_update(wwo->pcm);
    snd_pcm_hw_params_get_buffer_size(wwo->hw_params, &buf_size);
    delay = buf_size - avail;

    if (state != SND_PCM_STATE_RUNNING && state != SND_PCM_STATE_PREPARED)
    {
        WARN("Unexpected state (%d) while updating Total Played, resetting\n", state);
        wine_snd_pcm_recover(wwo->pcm, -EPIPE, 0);
        delay=0;
    }

    /* A delay < 0 indicates an underrun; for our purposes that's 0.  */
    if (delay < 0)
    {
        WARN("Unexpected delay (%ld) while updating Total Played, resetting\n", delay);
        delay=0;
    }

    InterlockedExchange((LONG*)&wwo->dwPlayedTotal, wwo->dwWrittenTotal - snd_pcm_frames_to_bytes(wwo->pcm, delay));
    return TRUE;
}

static void alsa_log(snd_pcm_hw_params_t* hw_params, snd_pcm_sw_params_t* sw_params)
{
	unsigned period_time;
	snd_pcm_uframes_t period_size;
	unsigned period_count;
	unsigned buffer_time;
	snd_pcm_uframes_t buffer_size;
	unsigned tick_time;

	snd_pcm_uframes_t xfer_align;

	snd_pcm_hw_params_get_period_time(hw_params, &period_time, 0);
	snd_pcm_hw_params_get_period_size(hw_params, &period_size, 0);
	snd_pcm_hw_params_get_periods(hw_params, &period_count, 0);
	snd_pcm_hw_params_get_buffer_time(hw_params, &buffer_time, 0);
	snd_pcm_hw_params_get_buffer_size(hw_params, &buffer_size);
	snd_pcm_hw_params_get_tick_time(hw_params, &tick_time, 0);

	log_std(("sound:alsa: hw period_time %g [us], period_size %d, periods %d, buffer_time %g [us], buffer_size %d, tick_time %g [us]\n",
		(double)(period_time / 1000000.0), (unsigned)period_size, (unsigned)period_count, (double)(buffer_time / 1000000.0), (unsigned)buffer_size, (double)(tick_time / 1000000.0)
	));

	snd_pcm_sw_params_get_xfer_align(sw_params, &xfer_align);
	log_std(("sound:alsa: sw xfer_align %d\n",
		(unsigned)xfer_align
	));
}

static
int set_hwparams(snd_pcm_t *handle,
                 snd_pcm_hw_params_t *params,
                 snd_pcm_access_t access)
{
    int err, dir;

    /* choose all parameters */
    err = snd_pcm_hw_params_any(handle,params);
    if (err < 0) {
        printf("Access type not available for playback: %s\n", snd_strerror(err));
        return err;
    }
    /* set the sample format */
    err = snd_pcm_hw_params_set_format(handle, params, alsa_format);
    if (err < 0) {
        printf("Sample format not available for playback: %s\n", snd_strerror(err));
        return err;
    }
    /* set the count of channels */
    err = snd_pcm_hw_params_set_channels(handle, params, channels);
    if (err < 0) {
        printf("Channels count (%i) not available for playbacks: %s\n", channels, snd_strerror(err));
        return err;
    }
    /* set the stream rate */
    err = snd_pcm_hw_params_set_rate_near(handle, params, rate, 0);
    if (err < 0) {
        printf("Rate %iHz not available for playback: %s\n", rate, snd_strerror(err));
        return err;
    }
    if (err != rate) {
        printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);
        return -EINVAL;
    }
    /* set buffer time */
    err = snd_pcm_hw_params_set_buffer_time_near(handle, params, buffer_time, &dir);
    if (err < 0) {
        printf("Unable to set buffer time %i for playback: %s\n", buffer_time, snd_strerror(err));
        return err;
    }
    buffer_size = snd_pcm_hw_params_get_buffer_size(params);
    /* set period time */
    err = snd_pcm_hw_params_set_period_time_near(handle, params, period_time, &dir);
    if (err < 0) {
        printf("Unable to set period time %i for playback: %s\n", period_time, snd_strerror(err));
        return err;
    }
    period_size = snd_pcm_hw_params_get_period_size(params, &dir);
    /* write the parameters to device */
    err = snd_pcm_hw_params(handle, params);
    if (err < 0) {
        printf("Unable to set hw params for playback: %s\n", snd_strerror(err));
        return err;
    }
    return 0;
}

static int alsa_set_hwparams()
{
	snd_pcm_hw_params_t *hwp;
	snd_pcm_sw_params_t *swp;
	int dir = 1;
	unsigned period_time;
	snd_pcm_uframes_t buffer_size, period_size;

	snd_pcm_hw_params_alloca(&hwp);
	snd_pcm_sw_params_alloca(&swp);

	// ALSA bug? If we request 44100 Hz, it rounds the value up to 48000...
	alsa_hw.rate--;

	if (alsa_error("hw_params_any", snd_pcm_hw_params_any(alsa_hw.handle, hwp))
	    || alsa_error("hw_params_set_format", snd_pcm_hw_params_set_format(alsa_hw.handle, hwp, alsa_hw.format))
	    || alsa_error("hw_params_set_channels",
			  snd_pcm_hw_params_set_channels(alsa_hw.handle, hwp, alsa_hw.num_channels))
	    || alsa_error("hw_params_set_rate_near",
			  snd_pcm_hw_params_set_rate_near(alsa_hw.handle, hwp, &alsa_hw.rate, &dir))
	    || alsa_error("hw_params_set_access",
			  snd_pcm_hw_params_set_access(alsa_hw.handle, hwp, SND_PCM_ACCESS_RW_INTERLEAVED))
	    || alsa_error("hw_params_set_buffer_time_near",
			  snd_pcm_hw_params_set_buffer_time_near(alsa_hw.handle, hwp, &alsa_hw.buffer_time, 0)))
		return -1;

	/* How often to call our SIGIO handler (~40Hz) */
	period_time = alsa_hw.buffer_time / 4;
	if (alsa_error
	    ("hw_params_set_period_time_near",
	     snd_pcm_hw_params_set_period_time_near(alsa_hw.handle, hwp, &period_time, &dir))
	    || alsa_error("hw_params_get_buffer_size", snd_pcm_hw_params_get_buffer_size(hwp, &buffer_size))
	    || alsa_error("hw_params_get_period_size", snd_pcm_hw_params_get_period_size(hwp, &period_size, 0))
	    || alsa_error("hw_params", snd_pcm_hw_params(alsa_hw.handle, hwp)))
		return -1;

	snd_pcm_sw_params_current(alsa_hw.handle, swp);
	if (alsa_error
	    ("sw_params_set_start_threshold", snd_pcm_sw_params_set_start_threshold(alsa_hw.handle, swp, period_size))
	    || alsa_error("sw_params_set_avail_min", snd_pcm_sw_params_set_avail_min(alsa_hw.handle, swp, period_size))
	    || alsa_error("sw_params", snd_pcm_sw_params(alsa_hw.handle, swp)))
		return -1;

	return 0;
}

    void alsa_print_info(snd_pcm_t * handle, snd_pcm_hw_params_t * hwp) {
        printf("device [%s] opened with\n",
               snd_pcm_name(handle));
        printf("\tstate=%s\n",
               snd_pcm_state_name(snd_pcm_state(handle)));
        unsigned int val, val2;
        snd_pcm_hw_params_get_access(hwp,
                                     (snd_pcm_access_t *) &val);
        printf("\taccess_type=%s\n",
               snd_pcm_access_name((snd_pcm_access_t)val));

        snd_pcm_hw_params_get_format(hwp, (snd_pcm_format_t *) &val);
        printf("\tformat=%s\n",
               snd_pcm_format_name((snd_pcm_format_t) val)
               );

        snd_pcm_hw_params_get_channels(hwp, &val);
        printf("\tchannels=%d\n", val);

        snd_pcm_hw_params_get_rate(hwp, &val, (int *) &val2);
        printf("\trate=%d fps\n", val);

        snd_pcm_hw_params_get_period_time(hwp,
                                          &val, (int *) &val2);
        printf("\tperiod_time=%d us\n", val);

        snd_pcm_uframes_t frames;
        snd_pcm_hw_params_get_period_size(hwp,
                                          &frames, (int *) &val2);
        printf("\tperiod_size=%d frames\n", (int)frames);

        snd_pcm_hw_params_get_buffer_size(hwp,
                                          (snd_pcm_uframes_t *) &val);
        printf("\tbuffer_size=%d frames\n", val);

        snd_pcm_hw_params_get_periods(hwp, &val, (int *) &val2);
        printf("\tperiods_per_buffer=%d periods\n", val);
    }

//.........这里部分代码省略.........
        format->channel_locations[0] = GAVL_CHID_FRONT_LEFT;
        format->channel_locations[1] = GAVL_CHID_FRONT_RIGHT;
        }
      }
    else
      {
      bg_log(BG_LOG_ERROR, LOG_DOMAIN,
             "snd_pcm_hw_params_set_channels failed (Format has %d channels)",
             format->num_channels);
      goto fail;
      }
    }
  
  /* Switch off driver side resampling */
#if SND_LIB_VERSION >= 0x010009
  snd_pcm_hw_params_set_rate_resample(ret, hw_params, 0);
#endif
  
  /* Samplerate */
  i_tmp = format->samplerate;
  if(snd_pcm_hw_params_set_rate_near(ret, hw_params,
                                     &i_tmp,
                                     0) < 0)
    {
    bg_log(BG_LOG_ERROR, LOG_DOMAIN, "snd_pcm_hw_params_set_rate_near failed");
    goto fail;
    }
  if(format->samplerate != i_tmp)
    {
    bg_log(BG_LOG_INFO, LOG_DOMAIN,
           "Samplerate %d not supported by device %s, using %d",
           format->samplerate, card, i_tmp);

    }
  format->samplerate = i_tmp;
  
  dir = 0;

  /* Buffer size */

  snd_pcm_hw_params_get_buffer_size_min(hw_params, &buffer_size_min);
  snd_pcm_hw_params_get_buffer_size_max(hw_params, &buffer_size_max);
  dir=0;
  snd_pcm_hw_params_get_period_size_min(hw_params, &period_size_min,&dir);
  dir=0;
  snd_pcm_hw_params_get_period_size_max(hw_params, &period_size_max,&dir);
  
  buffer_size = gavl_time_to_samples(format->samplerate, buffer_time);

  
  if(buffer_size > buffer_size_max)
    buffer_size = buffer_size_max;
  if(buffer_size < buffer_size_min)
    buffer_size = buffer_size_min;

  period_size = buffer_size / 8;
  buffer_size = period_size * 8;

  dir = 0;
  if(snd_pcm_hw_params_set_period_size_near(ret, hw_params, &period_size, &dir) < 0)
    {
    bg_log(BG_LOG_ERROR, LOG_DOMAIN, "snd_pcm_hw_params_set_period_size failed");
    goto fail;
    }
  dir = 0;
  snd_pcm_hw_params_get_period_size(hw_params, &period_size, &dir);

  dir = 0;
  if(snd_pcm_hw_params_set_buffer_size_near(ret, hw_params, &buffer_size) < 0)
    {
    bg_log(BG_LOG_ERROR, LOG_DOMAIN, "snd_pcm_hw_params_set_buffer_size failed");
    goto fail;
    }
  
  snd_pcm_hw_params_get_buffer_size(hw_params, &buffer_size);

  
  format->samples_per_frame = period_size;
  
  /* Write params to card */
  if(snd_pcm_hw_params (ret, hw_params) < 0)
    {
    bg_log(BG_LOG_ERROR, LOG_DOMAIN, "snd_pcm_hw_params failed");
    goto fail;
    }
  snd_pcm_hw_params_free(hw_params);
  
  gavl_set_channel_setup(format);
  //  gavl_audio_format_dump(format);
  
  return ret;
  fail:
  
  bg_log(BG_LOG_ERROR, LOG_DOMAIN, "Alsa initialization failed");
  if(ret)
    snd_pcm_close(ret);
  if(hw_params)
    snd_pcm_hw_params_free(hw_params);
  return NULL;
  }

static void *alsa_thread_init(const char *device,
      unsigned rate, unsigned latency)
{
   snd_pcm_uframes_t buffer_size;
   snd_pcm_format_t format;
   snd_pcm_hw_params_t *params    = NULL;
   snd_pcm_sw_params_t *sw_params = NULL;
   const char *alsa_dev           = device ? device : "default";
   unsigned latency_usec          = latency * 1000 / 2;
   unsigned channels              = 2;
   unsigned periods               = 4;
   alsa_thread_t            *alsa = (alsa_thread_t*)
      calloc(1, sizeof(alsa_thread_t));

   if (!alsa)
      return NULL;

   TRY_ALSA(snd_pcm_open(&alsa->pcm, alsa_dev, SND_PCM_STREAM_PLAYBACK, 0));

   TRY_ALSA(snd_pcm_hw_params_malloc(&params));
   alsa->has_float = alsathread_find_float_format(alsa->pcm, params);
   format = alsa->has_float ? SND_PCM_FORMAT_FLOAT : SND_PCM_FORMAT_S16;

   TRY_ALSA(snd_pcm_hw_params_any(alsa->pcm, params));
   TRY_ALSA(snd_pcm_hw_params_set_access(
            alsa->pcm, params, SND_PCM_ACCESS_RW_INTERLEAVED));
   TRY_ALSA(snd_pcm_hw_params_set_format(alsa->pcm, params, format));
   TRY_ALSA(snd_pcm_hw_params_set_channels(alsa->pcm, params, channels));
   TRY_ALSA(snd_pcm_hw_params_set_rate(alsa->pcm, params, rate, 0));

   TRY_ALSA(snd_pcm_hw_params_set_buffer_time_near(
            alsa->pcm, params, &latency_usec, NULL));
   TRY_ALSA(snd_pcm_hw_params_set_periods_near(
            alsa->pcm, params, &periods, NULL));

   TRY_ALSA(snd_pcm_hw_params(alsa->pcm, params));

   /* Shouldn't have to bother with this, 
    * but some drivers are apparently broken. */
   if (snd_pcm_hw_params_get_period_size(params, &alsa->period_frames, NULL))
      snd_pcm_hw_params_get_period_size_min(
            params, &alsa->period_frames, NULL);
   RARCH_LOG("ALSA: Period size: %d frames\n", (int)alsa->period_frames);
   if (snd_pcm_hw_params_get_buffer_size(params, &buffer_size))
      snd_pcm_hw_params_get_buffer_size_max(params, &buffer_size);
   RARCH_LOG("ALSA: Buffer size: %d frames\n", (int)buffer_size);

   alsa->buffer_size = snd_pcm_frames_to_bytes(alsa->pcm, buffer_size);
   alsa->period_size = snd_pcm_frames_to_bytes(alsa->pcm, alsa->period_frames);

   TRY_ALSA(snd_pcm_sw_params_malloc(&sw_params));
   TRY_ALSA(snd_pcm_sw_params_current(alsa->pcm, sw_params));
   TRY_ALSA(snd_pcm_sw_params_set_start_threshold(
            alsa->pcm, sw_params, buffer_size / 2));
   TRY_ALSA(snd_pcm_sw_params(alsa->pcm, sw_params));

   snd_pcm_hw_params_free(params);
   snd_pcm_sw_params_free(sw_params);

   alsa->fifo_lock = slock_new();
   alsa->cond_lock = slock_new();
   alsa->cond = scond_new();
   alsa->buffer = fifo_new(alsa->buffer_size);
   if (!alsa->fifo_lock || !alsa->cond_lock || !alsa->cond || !alsa->buffer)
      goto error;

   alsa->worker_thread = sthread_create(alsa_worker_thread, alsa);
   if (!alsa->worker_thread)
   {
      RARCH_ERR("error initializing worker thread");
      goto error;
   }

   return alsa;

error:
   RARCH_ERR("ALSA: Failed to initialize...\n");
   if (params)
      snd_pcm_hw_params_free(params);

   if (sw_params)
      snd_pcm_sw_params_free(sw_params);

   alsa_thread_free(alsa);

   return NULL;
}

static void set_params(void)
{
	snd_pcm_hw_params_t *params;
	snd_pcm_sw_params_t *swparams;
	snd_pcm_uframes_t buffer_size;
	int err;
	size_t n;
	snd_pcm_uframes_t xfer_align;
	unsigned int rate;
	snd_pcm_uframes_t start_threshold, stop_threshold;
	snd_pcm_hw_params_alloca(&params);
	snd_pcm_sw_params_alloca(&swparams);
	err = snd_pcm_hw_params_any(handle, params);
	if (err < 0) {
		error(_("Broken configuration for this PCM: no configurations available"));
		exit(EXIT_FAILURE);
	}
	err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
	if (err < 0) {
		error(_("Access type not available"));
		exit(EXIT_FAILURE);
	}
	err = snd_pcm_hw_params_set_format(handle, params, hwparams.format);
	if (err < 0) {
		error(_("Sample format non available"));
		exit(EXIT_FAILURE);
	}
	err = snd_pcm_hw_params_set_channels(handle, params, hwparams.channels);
	if (err < 0) {
		error(_("Channels count non available"));
		exit(EXIT_FAILURE);
	}

#if 0
	err = snd_pcm_hw_params_set_periods_min(handle, params, 2);
	assert(err >= 0);
#endif
	rate = hwparams.rate;
	err = snd_pcm_hw_params_set_rate_near(handle, params, &hwparams.rate, 0);
	assert(err >= 0);
	if ((float)rate * 1.05 < hwparams.rate || (float)rate * 0.95 > hwparams.rate) {
		if (!quiet_mode) {
			char plugex[64];
			const char *pcmname = snd_pcm_name(handle);
			fprintf(stderr, _("Warning: rate is not accurate (requested = %iHz, got = %iHz)\n"), rate, hwparams.rate);
			if (! pcmname || strchr(snd_pcm_name(handle), ':'))
				*plugex = 0;
			else
				snprintf(plugex, sizeof(plugex), "(-Dplug:%s)",
					 snd_pcm_name(handle));
			fprintf(stderr, _("         please, try the plug plugin %s\n"),
				plugex);
		}
	}
	rate = hwparams.rate;
	if (buffer_time == 0 && buffer_frames == 0) {
		err = snd_pcm_hw_params_get_buffer_time_max(params,
							    &buffer_time, 0);
		assert(err >= 0);
		if (buffer_time > 500000)
			buffer_time = 500000;
	}
	if (period_time == 0 && period_frames == 0) {
		if (buffer_time > 0)
			period_time = buffer_time / 4;
		else
			period_frames = buffer_frames / 4;
	}
	if (period_time > 0)
		err = snd_pcm_hw_params_set_period_time_near(handle, params,
							     &period_time, 0);
	else
		err = snd_pcm_hw_params_set_period_size_near(handle, params,
							     &period_frames, 0);
	assert(err >= 0);
	if (buffer_time > 0) {
		err = snd_pcm_hw_params_set_buffer_time_near(handle, params,
							     &buffer_time, 0);
	} else {
		err = snd_pcm_hw_params_set_buffer_size_near(handle, params,
							     &buffer_frames);
	}
	assert(err >= 0);
	err = snd_pcm_hw_params(handle, params);
	if (err < 0) {
		error(_("Unable to install hw params:"));
		snd_pcm_hw_params_dump(params, log);
		exit(EXIT_FAILURE);
	}
	snd_pcm_hw_params_get_period_size(params, &chunk_size, 0);
	snd_pcm_hw_params_get_buffer_size(params, &buffer_size);
	if (chunk_size == buffer_size) {
		error(_("Can't use period equal to buffer size (%lu == %lu)"),
		      chunk_size, buffer_size);
		exit(EXIT_FAILURE);
	}
	snd_pcm_sw_params_current(handle, swparams);
	err = snd_pcm_sw_params_get_xfer_align(swparams, &xfer_align);
	if (err < 0) {
		error(_("Unable to obtain xfer align\n"));
//.........这里部分代码省略.........

//.........这里部分代码省略.........
            goto retry;
        }
        GST_DEBUG_OBJECT (alsa, "buffer time %u", buffer_time);
    }
    if (period_time != -1 && !alsa->iec958) {
        /* set the period time */
        if ((err = snd_pcm_hw_params_set_period_time_near (alsa->handle, params,
                   &period_time, NULL)) < 0) {
            GST_ELEMENT_WARNING (alsa, RESOURCE, SETTINGS, (NULL),
                                 ("Unable to set period time %i for playback: %s",
                                  period_time, snd_strerror (err)));
            /* disable period_time the next round */
            period_time = -1;
            goto retry;
        }
        GST_DEBUG_OBJECT (alsa, "period time %u", period_time);
    }

    /* Set buffer size and period size manually for SPDIF */
    if (G_UNLIKELY (alsa->iec958)) {
        snd_pcm_uframes_t buffer_size = SPDIF_BUFFER_SIZE;
        snd_pcm_uframes_t period_size = SPDIF_PERIOD_SIZE;

        CHECK (snd_pcm_hw_params_set_buffer_size_near (alsa->handle, params,
                &buffer_size), buffer_size);
        CHECK (snd_pcm_hw_params_set_period_size_near (alsa->handle, params,
                &period_size, NULL), period_size);
    }

    /* write the parameters to device */
    CHECK (snd_pcm_hw_params (alsa->handle, params), set_hw_params);

    /* now get the configured values */
    CHECK (snd_pcm_hw_params_get_buffer_size (params, &alsa->buffer_size),
           buffer_size);
    CHECK (snd_pcm_hw_params_get_period_size (params, &alsa->period_size, NULL),
           period_size);

    GST_DEBUG_OBJECT (alsa, "buffer size %lu, period size %lu", alsa->buffer_size,
                      alsa->period_size);

    snd_pcm_hw_params_free (params);
    return 0;

    /* ERRORS */
no_config:
    {
        GST_ELEMENT_ERROR (alsa, RESOURCE, SETTINGS, (NULL),
                           ("Broken configuration for playback: no configurations available: %s",
                            snd_strerror (err)));
        snd_pcm_hw_params_free (params);
        return err;
    }
wrong_access:
    {
        GST_ELEMENT_ERROR (alsa, RESOURCE, SETTINGS, (NULL),
                           ("Access type not available for playback: %s", snd_strerror (err)));
        snd_pcm_hw_params_free (params);
        return err;
    }
no_sample_format:
    {
        GST_ELEMENT_ERROR (alsa, RESOURCE, SETTINGS, (NULL),
                           ("Sample format not available for playback: %s", snd_strerror (err)));
        snd_pcm_hw_params_free (params);
        return err;

int
ga_alsa_set_param(struct Xcap_alsa_param *param) {
	snd_pcm_hw_params_t *hwparams = NULL;
	snd_pcm_sw_params_t *swparams = NULL;
	size_t bits_per_sample;
	unsigned int rate;
	unsigned int buffer_time = 500000;	// in the unit of microsecond
	unsigned int period_time = 125000;	// = buffer_time/4;
	int monotonic = 0;
	snd_pcm_uframes_t start_threshold, stop_threshold;
	int err;
	//
	snd_pcm_hw_params_alloca(&hwparams);
	snd_pcm_sw_params_alloca(&swparams);
	if((err = snd_pcm_hw_params_any(param->handle, hwparams)) < 0) {
		ga_error("ALSA: set_param - no configurations available\n");
		return -1;
	}
	if((err = snd_pcm_hw_params_set_access(param->handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		ga_error("ALSA: set_param - access type (interleaved) not available\n");
		return -1;
	}
	if((err = snd_pcm_hw_params_set_format(param->handle, hwparams, param->format)) < 0) {
		ga_error("ALSA: set_param - unsupported sample format.\n");
		return -1;
	}
	if((err = snd_pcm_hw_params_set_channels(param->handle, hwparams, param->channels)) < 0) {
		ga_error("ALSA: set_param - channles count not available\n");
		return -1;
	}
	rate = param->samplerate;
	if((err = snd_pcm_hw_params_set_rate_near(param->handle, hwparams, &rate, 0)) < 0) {
		ga_error("ALSA: set_param - set rate failed.\n");
		return -1;
	}
	if((double)param->samplerate*1.05 < rate || (double)param->samplerate*0.95 > rate) {
		ga_error("ALSA: set_param/warning - inaccurate rate (req=%iHz, got=%iHz)\n", param->samplerate, rate);
	}
	//
	period_time = buffer_time/4;
	if((err = snd_pcm_hw_params_set_period_time_near(param->handle, hwparams, &period_time, 0)) < 0) {
		ga_error("ALSA: set_param - set period time failed.\n");
		return -1;
	}
	if((err = snd_pcm_hw_params_set_buffer_time_near(param->handle, hwparams, &buffer_time, 0)) < 0) {
		ga_error("ALSA: set_param - set buffer time failed.\n");
		return -1;
	}
	//
	monotonic = snd_pcm_hw_params_is_monotonic(hwparams);
	if((err = snd_pcm_hw_params(param->handle, hwparams)) < 0) {
		ga_error("ALSA: set_param - unable to install hw params:");
		snd_pcm_hw_params_dump(hwparams, sndlog);
		return -1;
	}
	snd_pcm_hw_params_get_period_size(hwparams, &param->chunk_size, 0);
	snd_pcm_hw_params_get_buffer_size(hwparams, &param->buffer_size);
	if(param->chunk_size == param->buffer_size) {
		ga_error("ALSA: set_param - cannot use period equal to buffer size (%lu==%lu)\n",
			param->chunk_size, param->buffer_size);
		return -1;
	}
	//
	snd_pcm_sw_params_current(param->handle, swparams);
	err = snd_pcm_sw_params_set_avail_min(param->handle, swparams, param->chunk_size);
	// start_delay = 1 for capture
	start_threshold = (double) param->samplerate * /*start_delay=*/ 1 / 1000000;
	if(start_threshold < 1)				start_threshold = 1;
	if(start_threshold > param->buffer_size)	start_threshold = param->buffer_size;
	if((err = snd_pcm_sw_params_set_start_threshold(param->handle, swparams, start_threshold)) < 0) {
		ga_error("ALSA: set_param - set start threshold failed.\n");
		return -1;
	}
	// stop_delay = 0
	stop_threshold = param->buffer_size;
	if((err = snd_pcm_sw_params_set_stop_threshold(param->handle, swparams, stop_threshold)) < 0) {
		ga_error("ALSA: set_param - set stop threshold failed.\n");
		return -1;
	}
	//
	if(snd_pcm_sw_params(param->handle, swparams) < 0) {
		ga_error("ALSA: set_param - unable to install sw params:");
		snd_pcm_sw_params_dump(swparams, sndlog);
		return -1;
	}

	bits_per_sample = snd_pcm_format_physical_width(param->format);
	if(param->bits_per_sample != bits_per_sample) {
		ga_error("ALSA: set_param - BPS/HW configuration mismatched %d != %d)\n",
			param->bits_per_sample, bits_per_sample);
	}
	param->bits_per_frame = param->bits_per_sample * param->channels;
	param->chunk_bytes = param->chunk_size * param->bits_per_frame / 8;

	return 0;
}

static snd_pcm_t *alsa_open(snd_pcm_t **pcm_handle, int stream_type,
        snd_pcm_uframes_t *buffer_size) {
    char                *pcm_name = "chumix";
    snd_pcm_hw_params_t *hwparams;
    snd_pcm_sw_params_t *swparams;
    unsigned int         buffer_time;
    int                  status;
    snd_pcm_uframes_t    xfer_align;


    // Open the device.  Experimenting with duplex mode.
    fprintf(stderr, "Opening PCM device\n");
    status = snd_pcm_open(pcm_handle, pcm_name,
                          stream_type, 0);
    if(status < 0) {
        fprintf(stderr, "Unable to open audio device: %s\n",
                snd_strerror(status));
        goto error;
    }


    // Determine what the hardware can do.
    fprintf(stderr, "Allocating hw params\n");
    snd_pcm_hw_params_malloc(&hwparams);
    status = snd_pcm_hw_params_any(*pcm_handle, hwparams);
    if(status < 0) {
        fprintf(stderr, "Unable to get hardware parameters: %s\n",
                snd_strerror(status));
        goto error;
    }


    // Set up interleaved audio.
    fprintf(stderr, "Setting up interleaved audio\n");
    status = snd_pcm_hw_params_set_access(*pcm_handle, hwparams,
                                          SND_PCM_ACCESS_RW_INTERLEAVED);
    if(status < 0) {
        fprintf(stderr, "Unable to set interleaved mode: %s\n",
                snd_strerror(status));
        goto error;
    }


    // Set the audio format.
    fprintf(stderr, "Setting format\n");
    status = snd_pcm_hw_params_set_format(*pcm_handle, hwparams,
                                          SND_PCM_FORMAT_S16_LE);
    if(status<0) {
        fprintf(stderr, "Unable to set audio format: %s\n",
                snd_strerror(status));
        goto error;
    }


    // Set stereo audio.
    fprintf(stderr, "Setting channels\n");
    status = snd_pcm_hw_params_set_channels(*pcm_handle, hwparams, 2);
    if(status<0) {
        fprintf(stderr, "Unable to set stereo mode: %s\n",
                snd_strerror(status));
        goto error;
    }


    // Set sample rate.
    fprintf(stderr, "Setting audio rate\n");
    int rate = 44100;
    status = snd_pcm_hw_params_set_rate_near(*pcm_handle, hwparams,
                                             &rate, NULL);
    if(status<0) {
        fprintf(stderr, "Unable to set sample rate to 44100: %s\n",
                snd_strerror(status));
        goto error;
    }

    // Set buffer time to a reasonable value.
    // Probably won't work for playback, as it's fixed in /etc/asound.conf
    buffer_time = BUFFER_TIME;
    status = snd_pcm_hw_params_set_buffer_time_near(*pcm_handle, hwparams,
                                                         &buffer_time, 0);
    snd_pcm_hw_params_get_buffer_size(hwparams, buffer_size);


    // Write the settings out to the audio card.
    fprintf(stderr, "Setting hw params\n");
    status = snd_pcm_hw_params(*pcm_handle, hwparams);
    if(status<0) {
        fprintf(stderr, "Unable to set audio parameters: %s\n",
                snd_strerror(status));
        goto error;
    }

    snd_pcm_hw_params_free(hwparams);

    status = snd_pcm_prepare(*pcm_handle);
    if(status<0) {
        fprintf(stderr, "Unable to prepare audio device: %s\n",
                snd_strerror(status));
        goto error;
    }
//.........这里部分代码省略.........

    bool open()
    {
        // Open the Alsa playback device.
        int err=-1,count=0;
        unsigned int        freakuency = frequency;

        while((count < 5) && (err < 0)) {
            err = snd_pcm_open
                  ( &handle,  ALSA_OUTPUT_NAME, SND_PCM_STREAM_PLAYBACK, 0 );

            if(err < 0) {
                count++;
                qWarning()<<"QAudioOutput::open() err="<<err<<", count="<<count;
            }
        }
        if (( err < 0)||(handle == 0)) {
            qWarning( "QAudioOuput: snd_pcm_open: error %d", err );
            return false;
        }
        snd_pcm_nonblock( handle, 0 );

        // Set the desired HW parameters.
        snd_pcm_hw_params_t *hwparams;
        snd_pcm_hw_params_alloca( &hwparams );

        err = snd_pcm_hw_params_any( handle, hwparams );
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_any: err %d", err);
            return false;
        }

        err = snd_pcm_hw_params_set_access( handle, hwparams, access );
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_access: err %d", err);
            return false;
        }

        err = snd_pcm_hw_params_set_format( handle, hwparams,
             ( bitsPerSample == 16 ? SND_PCM_FORMAT_S16
                                   : SND_PCM_FORMAT_U8 ) );
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_format: err %d", err);
            return false;
        }

        err = snd_pcm_hw_params_set_channels
            ( handle, hwparams, (unsigned int)channels );
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_channels: err %d", err);
            return false;
        }

        err = snd_pcm_hw_params_set_rate_near
            ( handle, hwparams, &freakuency, 0 );
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_rate_near: err %d", err);
            return false;
        }

#ifndef ALSA_BUFFER_SIZE
        err = snd_pcm_hw_params_set_buffer_time_near(handle, hwparams, &buffer_time, 0);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_buffer_time_near: err %d",err);
        }
        err = snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_get_buffer_size: err %d",err);
        }
#else
        buffer_size = ALSA_BUFFER_SIZE;
        err = snd_pcm_hw_params_set_buffer_size_near(handle, hwparams, &buffer_size);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_buffer_time_near: err %d",err);
        }
#endif

#ifndef ALSA_PERIOD_SIZE
        period_time = buffer_time/4;
        err = snd_pcm_hw_params_set_period_time_near(handle, hwparams, &period_time, 0);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_period_time_near: err %d",err);
        }
#else
        period_size = ALSA_PERIOD_SIZE;
        err = snd_pcm_hw_params_set_period_size_near(handle, hwparams, &period_size, 0);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params_set_period_size_near: err %d",err);
        }
#endif

        err = snd_pcm_hw_params(handle, hwparams);
        if ( err < 0 ) {
            qWarning( "QAudioOutput: snd_pcm_hw_params: err %d", err);
            return false;
        }

        int                  dir;
        unsigned int         vval, vval2;
        snd_pcm_access_t     val;
        snd_pcm_format_t     fval;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
							    &buffer_time, 0);
		assert(err >= 0);
		if (buffer_time > 500000)
			buffer_time = 500000;
	}
	if (period_time == 0 && period_frames == 0) {
		if (buffer_time > 0)
			period_time = buffer_time / 4;
		else
			period_frames = buffer_frames / 4;
	}
	if (period_time > 0)
		err = snd_pcm_hw_params_set_period_time_near(handle, params,
							     &period_time, 0);
	else
		err = snd_pcm_hw_params_set_period_size_near(handle, params,
							     &period_frames, 0);
	assert(err >= 0);
	if (buffer_time > 0) {
		err = snd_pcm_hw_params_set_buffer_time_near(handle, params,
							     &buffer_time, 0);
	} else {
		err = snd_pcm_hw_params_set_buffer_size_near(handle, params,
							     &buffer_frames);
	}
	assert(err >= 0);
	err = snd_pcm_hw_params(handle, params);
	if (err < 0) {
		error("Unable to install hw params:");
		snd_pcm_hw_params_dump(params, log);
		exit(EXIT_FAILURE);
	}
	snd_pcm_hw_params_get_period_size(params, &chunk_size, 0);
	snd_pcm_hw_params_get_buffer_size(params, &buffer_size);
	if (chunk_size == buffer_size) {
		error("Can't use period equal to buffer size (%lu == %lu)",
		      chunk_size, buffer_size);
		exit(EXIT_FAILURE);
	}
	snd_pcm_sw_params_current(handle, swparams);
	if (avail_min < 0)
		n = chunk_size;
	else
		n = (double) rate * avail_min / 1000000;
	err = snd_pcm_sw_params_set_avail_min(handle, swparams, n);
	if (err < 0) {
		error("Setting sw params failed\n");
	}

	/* round up to closest transfer boundary */
	n = buffer_size;
	if (start_delay <= 0) {
		start_threshold = n + (double) rate * start_delay / 1000000;
	} else
		start_threshold = (double) rate * start_delay / 1000000;
	if (start_threshold < 1)
		start_threshold = 1;
	if (start_threshold > n)
		start_threshold = n;
	err = snd_pcm_sw_params_set_start_threshold(handle, swparams, start_threshold);
	assert(err >= 0);
	if (stop_delay <= 0) 
		stop_threshold = buffer_size + (double) rate * stop_delay / 1000000;
	else
		stop_threshold = (double) rate * stop_delay / 1000000;
	err = snd_pcm_sw_params_set_stop_threshold(handle, swparams, stop_threshold);

//.........这里部分代码省略.........
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_access( handle, hwparams, access );
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_access: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = setFormat();
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_format: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_channels( handle, hwparams, (unsigned int)settings.channelCount() );
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_channels: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_rate_near( handle, hwparams, &sampleRate, 0 );
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_rate_near: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_buffer_time_near(handle, hwparams, &buffer_time, &dir);
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_buffer_time_near: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_period_time_near(handle, hwparams, &period_time, &dir);
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_period_time_near: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params_set_periods_near(handle, hwparams, &chunks, &dir);
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params_set_periods_near: err = %1").arg(err);
        }
    }
    if ( !fatal ) {
        err = snd_pcm_hw_params(handle, hwparams);
        if ( err < 0 ) {
            fatal = true;
            errMessage = QString::fromLatin1("QAudioInput: snd_pcm_hw_params: err = %1").arg(err);
        }
    }
    if( err < 0) {
        qWarning()<<errMessage;
        errorState = QAudio::OpenError;
        deviceState = QAudio::StoppedState;
        emit stateChanged(deviceState);
        return false;
    }
    snd_pcm_hw_params_get_buffer_size(hwparams,&buffer_frames);
    buffer_size = snd_pcm_frames_to_bytes(handle,buffer_frames);
    snd_pcm_hw_params_get_period_size(hwparams,&period_frames, &dir);
    period_size = snd_pcm_frames_to_bytes(handle,period_frames);
    snd_pcm_hw_params_get_buffer_time(hwparams,&buffer_time, &dir);
    snd_pcm_hw_params_get_period_time(hwparams,&period_time, &dir);

    // Step 3: Set the desired SW parameters.
    snd_pcm_sw_params_t *swparams;
    snd_pcm_sw_params_alloca(&swparams);
    snd_pcm_sw_params_current(handle, swparams);
    snd_pcm_sw_params_set_start_threshold(handle,swparams,period_frames);
    snd_pcm_sw_params_set_stop_threshold(handle,swparams,buffer_frames);
    snd_pcm_sw_params_set_avail_min(handle, swparams,period_frames);
    snd_pcm_sw_params(handle, swparams);

    // Step 4: Prepare audio
    ringBuffer.resize(buffer_size);
    snd_pcm_prepare( handle );
    snd_pcm_start(handle);

    // Step 5: Setup timer
    bytesAvailable = checkBytesReady();

    if(pullMode)
        connect(audioSource,SIGNAL(readyRead()),this,SLOT(userFeed()));

    // Step 6: Start audio processing
    chunks = buffer_size/period_size;
    timer->start(period_time*chunks/2000);

    errorState  = QAudio::NoError;

    totalTimeValue = 0;

    return true;
}

//.........这里部分代码省略.........
    err = snd_pcm_hw_params_set_rate_near(sndpcm->handle,
                                          params, &bat->rate,
                                          0);
    if (err < 0) {
        loge(E_SETDEV S_SAMPLERATE, "%d %s: %s(%d)",
             bat->rate,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }
    if ((float) rate * 1.05 < bat->rate
            || (float) rate * 0.95 > bat->rate) {
        loge(E_PARAMS S_SAMPLERATE, "requested %dHz, got %dHz",
             rate, bat->rate);
        goto fail_exit;
    }

    if (snd_pcm_hw_params_get_buffer_time_max(params,
            &buffer_time, 0) < 0) {
        loge(E_GETDEV S_BUFFERTIME, "%d %s: %s(%d)",
             buffer_time,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    if (buffer_time > 500000)
        buffer_time = 500000;
    /* Was 4, changed to 8 to remove reduce capture overrun */
    period_time = buffer_time / 8;

    /* Set buffer time and period time */
    err = snd_pcm_hw_params_set_buffer_time_near(sndpcm->handle, params,
            &buffer_time, 0);
    if (err < 0) {
        loge(E_SETDEV S_BUFFERTIME, "%d %s: %s(%d)",
             buffer_time,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    err = snd_pcm_hw_params_set_period_time_near(sndpcm->handle, params,
            &period_time, 0);
    if (err < 0) {
        loge(E_SETDEV S_PERIODTIME, "%d %s: %s(%d)",
             period_time,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    /* Write the parameters to the driver */
    if (snd_pcm_hw_params(sndpcm->handle, params) < 0) {
        loge(E_SETDEV S_HWPARAMS, "%s: %s(%d)",
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    err = snd_pcm_hw_params_get_period_size(params,
                                            &sndpcm->period_size, 0);
    if (err < 0) {
        loge(E_GETDEV S_PERIODSIZE, "%zd %s: %s(%d)",
             sndpcm->period_size,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    err = snd_pcm_hw_params_get_buffer_size(params, &sndpcm->buffer_size);
    if (err < 0) {
        loge(E_GETDEV S_BUFFERSIZE, "%zd %s: %s(%d)",
             sndpcm->buffer_size,
             device_name, snd_strerror(err), err);
        goto fail_exit;
    }

    if (sndpcm->period_size == sndpcm->buffer_size) {
        loge(E_PARAMS, "can't use period equal to buffer size (%zd)",
             sndpcm->period_size);
        goto fail_exit;
    }

    err = snd_pcm_format_physical_width(format);
    if (err < 0) {
        loge(E_PARAMS, "snd_pcm_format_physical_width: %d", err);
        goto fail_exit;
    }
    sndpcm->sample_bits = err;

    sndpcm->frame_bits = sndpcm->sample_bits * bat->channels;

    /* Calculate the period bytes */
    sndpcm->period_bytes = sndpcm->period_size * sndpcm->frame_bits / 8;
    sndpcm->buffer = (char *) malloc(sndpcm->period_bytes);
    if (sndpcm->buffer == NULL) {
        loge(E_MALLOC, "size=%zd", sndpcm->period_bytes);
        goto fail_exit;
    }

    return 0;

fail_exit:
    return -1;
}