C++ snd_pcm_hw_params_get_period_size函数代码示例

void SoundPlayer::main()
{
  BH_TRACE_INIT("SoundPlayer");
  unsigned i;
  for(i = 0; i < retries; ++i)
  {
    if(snd_pcm_open(&handle, "hw:0", SND_PCM_STREAM_PLAYBACK, 0) >= 0)
      break;
    Thread::sleep(retryDelay);
  }
  ASSERT(i < retries);
  snd_pcm_hw_params_t* params;
  VERIFY(!snd_pcm_hw_params_malloc(&params));
  VERIFY(!snd_pcm_hw_params_any(handle, params));
  VERIFY(!snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED));
  VERIFY(!snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE));
  VERIFY(!snd_pcm_hw_params_set_rate_near(handle, params, &sampleRate, 0));;
  VERIFY(!snd_pcm_hw_params_set_channels(handle, params, 2));
  VERIFY(!snd_pcm_hw_params(handle, params));
  VERIFY(!snd_pcm_hw_params_get_period_size(params, &periodSize, 0));
  snd_pcm_hw_params_free(params);

  while(isRunning() && !closing)
  {
    flush();
    VERIFY(sem.wait());
  }
  VERIFY(!snd_pcm_close(handle));
}

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
	));
}

void audio_init(void)
{
    int ret, dir;
    unsigned int rate;
    snd_pcm_hw_params_t * params;

    rate = 44100;
    frames = 32;
    ret = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0);

    if (ret < 0)
    {
        fprintf(stderr, "Unable to open pcm device: %s\n", snd_strerror(ret));
        exit(EXIT_FAILURE);
    }

    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(handle, params);
    snd_pcm_hw_params_set_access(handle, params, 
            SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(handle, params, 2);
    snd_pcm_hw_params_set_rate_near(handle, params, &rate, &dir);
    snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);

    ret = snd_pcm_hw_params(handle, params);
    
    if (ret < 0)
    {
        fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(ret));
        exit(EXIT_FAILURE);
    }

    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
}

/**************************************************************************
 * 				wodPlayer_NotifyCompletions	[internal]
 *
 * Notifies and remove from queue all wavehdrs which have been played to
 * the speaker (ie. they have cleared the ALSA buffer).  If force is true,
 * we notify all wavehdrs and remove them all from the queue even if they
 * are unplayed or part of a loop.
 */
static DWORD wodPlayer_NotifyCompletions(WINE_WAVEDEV* wwo, BOOL force)
{
    LPWAVEHDR		lpWaveHdr;

    /* Start from lpQueuePtr and keep notifying until:
     * - we hit an unwritten wavehdr
     * - we hit the beginning of a running loop
     * - we hit a wavehdr which hasn't finished playing
     */
    for (;;)
    {
        lpWaveHdr = wwo->lpQueuePtr;
        if (!lpWaveHdr) {TRACE("Empty queue\n"); break;}
        if (!force)
        {
            snd_pcm_uframes_t frames;
            snd_pcm_hw_params_get_period_size(wwo->hw_params, &frames, NULL);

            if (lpWaveHdr == wwo->lpPlayPtr) {TRACE("play %p\n", lpWaveHdr); break;}
            if (lpWaveHdr == wwo->lpLoopPtr) {TRACE("loop %p\n", lpWaveHdr); break;}
            if (lpWaveHdr->reserved > wwo->dwPlayedTotal + frames) {TRACE("still playing %p (%lu/%u)\n", lpWaveHdr, lpWaveHdr->reserved, wwo->dwPlayedTotal);break;}
        }
        wwo->dwPlayedTotal += lpWaveHdr->reserved - wwo->dwPlayedTotal;
	wwo->lpQueuePtr = lpWaveHdr->lpNext;

	lpWaveHdr->dwFlags &= ~WHDR_INQUEUE;
	lpWaveHdr->dwFlags |= WHDR_DONE;

	wodNotifyClient(wwo, WOM_DONE, (DWORD_PTR)lpWaveHdr, 0);
    }
    return  (lpWaveHdr && lpWaveHdr != wwo->lpPlayPtr && lpWaveHdr != wwo->lpLoopPtr) ?
        wodPlayer_NotifyWait(wwo, lpWaveHdr) : INFINITE;
}

void initsound(int samplerate, int channels)
{
    
    int dir, pcmrc;


    /* Open the PCM device in playback mode */
    snd_pcm_open(&pcm_handle, PCM_DEVICE, SND_PCM_STREAM_PLAYBACK, 0);

    /* Allocate parameters object and fill it with default values*/
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(pcm_handle, params);
    /* Set parameters */
    snd_pcm_hw_params_set_access(pcm_handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(pcm_handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(pcm_handle, params, channels);
    snd_pcm_hw_params_set_rate(pcm_handle, params, samplerate, 0);

    /* Write parameters */
    snd_pcm_hw_params(pcm_handle, params);


	
    /* Allocate buffer to hold single period */
    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    buf = malloc(frames * channels * 2 * BUFFER_NUM);
	
}

/**
 * This method will determine, based upon the size of each frame and the number of frames between interrupts the required size of the buffer that is to store the data.
 * @return
 */
int AudioInterface::getRequiredBufferSize() {
	int dir;
	int size;
	snd_pcm_hw_params_get_period_size(params, &frames, &dir);
	size = frames * this->channels * 2; /* 2 bytes/sample */
    std::cout << "Get re: " << channels << ":" << frames << std::endl;
	return size;
}

bool SoundProcessor::SetUpRecorder(){
  rc_m = snd_pcm_open(&handle_m, "default",
                    SND_PCM_STREAM_CAPTURE, 0);
  if (rc_m < 0) {
    fprintf(stderr,
            "unable to open pcm device: %s\n",
            snd_strerror(rc_m));
    exit(1);
  }

  /* Allocate a hardware parameters object. */
  snd_pcm_hw_params_alloca(&params_m);

  /* Fill it in with default values. */
  snd_pcm_hw_params_any(handle_m, params_m);

  /* Set the desired hardware parameters. */

  /* Interleaved mode */
  snd_pcm_hw_params_set_access(handle_m, params_m,
                      SND_PCM_ACCESS_RW_INTERLEAVED);

  /* Signed 16-bit little-endian format */
  snd_pcm_hw_params_set_format(handle_m, params_m,
                              SND_PCM_FORMAT_U8);

  /* Two channels (stereo) */
  snd_pcm_hw_params_set_channels(handle_m, params_m, 1);

  /* 44100 bits/second sampling rate (CD quality) */
  val_m = 8000;
  snd_pcm_hw_params_set_rate_near(handle_m, params_m,
                                  &val_m, &dir_m);

  /* Set period size to 32 frames. */
  //frames = 32;
  snd_pcm_hw_params_set_period_size_near(handle_m,
                              params_m, &frames, &dir_m);

  /* Write the parameters to the driver */
  rc_m = snd_pcm_hw_params(handle_m, params_m);
  if (rc_m < 0) {
    fprintf(stderr,
            "unable to set hw parameters: %s\n",
            snd_strerror(rc_m));
    exit(1);
  }

  /* Use a buffer large enough to hold one period */
  snd_pcm_hw_params_get_period_size(params_m,
                                      &frames, &dir_m);
  size = frames; /* 2 bytes/sample, 2 channels */
  buffer_m = (char *) malloc(size);
  /* We want to loop for 5 seconds */
  snd_pcm_hw_params_get_period_time(params_m,
                                         &val_m, &dir_m);
  return true;
}

void Recorder::initRecoder()
{
    int rc;
    snd_pcm_hw_params_t *params;
    unsigned int val;
    int dir=0;
    /* Open PCM device for recording (capture). */
    rc = snd_pcm_open(&handle, "default",SND_PCM_STREAM_CAPTURE, 0);
    if (rc < 0) {
        fprintf(stderr,"unable to open pcm device: %s\n",snd_strerror(rc));
        exit(1);
    }

    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(&params);

    /* Fill it in with default values. */
    snd_pcm_hw_params_any(handle, params);

    /* Set the desired hardware parameters. */

    /* Interleaved mode */
    snd_pcm_hw_params_set_access(handle, params,
                          SND_PCM_ACCESS_RW_INTERLEAVED);

    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(handle, params,SND_PCM_FORMAT_S16_LE);

    /* Two channels (stereo) */
    snd_pcm_hw_params_set_channels(handle, params, CHANNELS);

    /* 44100 bits/second sampling rate (CD quality) */
    val = SAMPLERATE;
    snd_pcm_hw_params_set_rate_near(handle, params,
                                      &val, &dir);

    /* Set period size to 32 frames. */
    frames = 32;
    snd_pcm_hw_params_set_period_size_near(handle,
                                  params, &frames, &dir);

    /* Write the parameters to the driver */
    rc = snd_pcm_hw_params(handle, params);
    if (rc < 0)
    {
        fprintf(stderr,"unable to set hw parameters: %s\n",snd_strerror(rc));
        exit(1);
    }

    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(params,&frames, &dir);
    size = frames * 2; /* 2 bytes/sample, 2 channels */

    /* We want to loop for 5 seconds */
    snd_pcm_hw_params_get_period_time(params,&val, &dir);
    //loops = 5000000 / val;  //获取5秒中所对应的loop这里用不到

}

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;
}

int audio_capture_init(char *audio_dev)
{
	unsigned int val;
	int dir, rc, size;

	/* Open PCM device for recording (capture). */
	rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_CAPTURE, 0);
	if (rc < 0) {
		fprintf(stderr, "unable to open pcm device: %s\n", snd_strerror(rc));
		return -1;
	}

	/* Allocate a hardware parameters object. */
	snd_pcm_hw_params_alloca(&hw_params);

	/* Fill it in with default values. */
	snd_pcm_hw_params_any(handle, hw_params);

	/* Set the desired hardware parameters. */

	/* Interleaved mode */
	snd_pcm_hw_params_set_access(handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);

	/* Signed 16-bit little-endian format */
	snd_pcm_hw_params_set_format(handle, hw_params, SND_PCM_FORMAT_S16_LE);

	/* 1 channel mono */
	snd_pcm_hw_params_set_channels(handle, hw_params, 1);

	/* 44100 bits/second sampling rate (CD quality) */
	val = 44100;
	snd_pcm_hw_params_set_rate_near(handle, hw_params, &val, &dir);

	/* Set period size to 32 frames. */
	frames = 32;
	snd_pcm_hw_params_set_period_size_near(handle, hw_params, &frames, &dir);

	/* Write the parameters to the driver */
	rc = snd_pcm_hw_params(handle, hw_params);
	if (rc < 0) {
		fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(rc));
		return -1;
	}

	/* Use a buffer large enough to hold one period */
	snd_pcm_hw_params_get_period_size(hw_params, &frames, &dir);
	size = frames * 4;	/* 2 bytes/sample, 2 channels */
	frame_buffer = (char *) malloc(size);
	printf("- Allocated %d bytes frame buffer\n", size);

	snd_pcm_hw_params_get_period_time(hw_params, &val, &dir);

	return 0;
}

static void set_params(void)
{
	hwparams.format=SND_PCM_FORMAT_S16_LE;
        hwparams.channels=2;
        hwparams.rate=44100;

	snd_pcm_hw_params_t *params;
	snd_pcm_sw_params_t *swparams;

        snd_pcm_hw_params_alloca(&params);
	snd_pcm_sw_params_alloca(&swparams);	

	snd_pcm_hw_params_any(handle, params);
	snd_pcm_hw_params_set_format(handle, params, hwparams.format);
	snd_pcm_hw_params_set_channels(handle, params, hwparams.channels);
	snd_pcm_hw_params_set_rate_near(handle, params, &hwparams.rate, 0);

	buffer_time=0;
	snd_pcm_hw_params_get_buffer_time_max(params,&buffer_time, 0);

	period_time=125000;
	snd_pcm_hw_params_set_period_time_near(handle, params,&period_time, 0);

	buffer_time = 500000;
	snd_pcm_hw_params_set_buffer_time_near(handle, params, &buffer_time, 0);
	
	/*monotonic = */snd_pcm_hw_params_is_monotonic(params);
        /*can_pause = */snd_pcm_hw_params_can_pause(params);

	
	printf("sizeof(params) : %d\n",sizeof(params));

        snd_pcm_hw_params(handle, params);

        snd_pcm_uframes_t buffer_size;
	snd_pcm_hw_params_get_period_size(params, &chunk_size, 0);

	size_t n=chunk_size;

	snd_pcm_sw_params_set_avail_min(handle, swparams, n);


	snd_pcm_uframes_t start_threshold, stop_threshold;	
	start_threshold=22050;
	snd_pcm_sw_params_set_start_threshold(handle, swparams, start_threshold);
	stop_threshold=22050;
	snd_pcm_sw_params_set_stop_threshold(handle, swparams, stop_threshold);
	
	snd_pcm_format_physical_width(hwparams.format);
	
}

/****************************************************************************************
*   函数名: init_alsa_play
*   输  入: 无
*   输  出: 无
*   功能说明：alsa音频播放器初始化
*
*       
******************************************************************************************/
void init_alsa_play()
{
		snd_pcm_hw_params_t *params; 
		unsigned int val; 
		int dir; 
				
		/* Open PCM device for playback. */
		rc=snd_pcm_open(&handle,"plughw:0,0", SND_PCM_STREAM_PLAYBACK, 0);
		if (rc< 0) 
		{ 
			fprintf(stderr,  "unable to open pcm device: %s\n",    snd_strerror(rc));
			exit(1); 
		} 
		 
		/* Allocate a hardware parameters object. */
		 snd_pcm_hw_params_alloca(&params); 
		/* Fill it in with default values. */
		 snd_pcm_hw_params_any(handle, params);
		 /* Set the desired hardware parameters. */ 

		/* Interleaved mode */ 
		snd_pcm_hw_params_set_access(handle,params, SND_PCM_ACCESS_RW_INTERLEAVED); 

		/* Signed 16-bit little-endian format 格式*/ 
		snd_pcm_hw_params_set_format(handle,params, SND_PCM_FORMAT_S16_LE); 


		/* Two channels (stereo) 声道*/  
		snd_pcm_hw_params_set_channels(handle, params, channels); 
		/* 32000 bits/second sampling rate (CD quality) 采样率设置*/ 
		snd_pcm_hw_params_set_rate_near(handle,params, &rate, &dir);  /* Set period size to 32 frames. */ 
		frames = SAMPLERATE/1000*READMSFORONCE; 
		snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
		/* Write the parameters to the driver */
		 rc = snd_pcm_hw_params(handle, params);
		 if (rc < 0) 
		 {   
				fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(rc));   
				exit(1); 
		}

		/*Use a buffer large enough to hold one period*/
		snd_pcm_hw_params_get_period_size(params, &frames,  &dir); //32个采样点算一帧
		size = frames * (channels);
		/* 2 bytes/sample, 2 channels */ 
		buffer = (char *) malloc(size); 
		/* We want to loop for 5 seconds */
		snd_pcm_hw_params_get_period_time(params, &val, &dir); 
}

void
carmen_sound_set_device_parameters(snd_pcm_t *handle, int sampling_rate, int num_frames)
{
	int rc, dir;
	unsigned int val;
	snd_pcm_hw_params_t *params;
	snd_pcm_uframes_t frames;

	val = sampling_rate;
	frames = (snd_pcm_uframes_t) num_frames;

	/* Allocate a hardware parameters object. */
	snd_pcm_hw_params_alloca(&params);

	/* Fill it in with default values. */
	snd_pcm_hw_params_any(handle, params);

	/* Interleaved mode */
	snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);

	/* Signed 16-bit little-endian format */
	snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);

	/* Two channels (stereo) */
	snd_pcm_hw_params_set_channels(handle, params, 2);

	/* set bits/second sampling rate */
	snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);

	/* Set period size to num of frames. */
	snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);

	/* Write the parameters to the driver */
	rc = snd_pcm_hw_params(handle, params);

	if (rc < 0)
		exit(printf("unable to set hw parameters: %s\n", snd_strerror(rc)));

	/* Use a buffer large enough to hold one period */
	snd_pcm_hw_params_get_period_size(params, &frames, &dir);

	/* We want to loop for 5 seconds */
	snd_pcm_hw_params_get_period_time(params, &val, &dir);

	// @TODO: pesquisar por que tem que ler um pouco que vem vazio nao sei por que...
	char buffer[4 * 32];
	rc = snd_pcm_readi(handle, buffer, 32);
}

void AudioWalkera::setupAlsa(){

	int dir;

	int t = 0, i, c;

	rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_CAPTURE, 0);

	if(rc < 0)
		exitError("Could not open pcm device");

	snd_pcm_hw_params_alloca(&params);
	//rc = setupHardware(handle, params, &dir);


	snd_pcm_uframes_t frames_inner;
	unsigned int val;

	snd_pcm_hw_params_any(handle, params);

	snd_pcm_hw_params_set_access(handle, params, 
			SND_PCM_ACCESS_RW_INTERLEAVED);

	snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);

	snd_pcm_hw_params_set_channels(handle, params, 1);


	val = 48000;
	snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);

	frames_inner = 2304;
	snd_pcm_hw_params_set_period_size_near(handle, params, &frames_inner, &dir);

	rc = snd_pcm_hw_params(handle, params);
 

	if(rc < 0)
		exitError("Could not set hardware parameters");

	snd_pcm_hw_params_get_period_size(params, &frames, &dir);

	buffer = (short*) calloc(frames, sizeof(short));


}

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;
}