C++ snd_pcm_hw_params_alloca函数代码示例

// Initialize the BlockSound class
BlockSound::BlockSound() {
	sample_size = 0;

#ifdef __APPLE__
	remaining = 0;

	UInt32 size = sizeof(device);

	if (AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice,
				&size, (void *)&device) != noErr) return;

	size = sizeof(format);
	if (AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat,
				&size, &format) != noErr) return;

	// Set up a format we like...
	format.mSampleRate       = 44100.0;	// 44.1kHz
	format.mChannelsPerFrame = 2;		// stereo

	if (AudioDeviceSetProperty(device, NULL, 0, false,
				kAudioDevicePropertyStreamFormat,
				sizeof(format), &format) != noErr) return;

	// Check we got linear pcm - what to do if we did not ???
	if (format.mFormatID != kAudioFormatLinearPCM) return;

	// Attach the callback and start the device
#  if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5
	if (AudioDeviceCreateIOProcID(device, audio_cb, (void *)this, &audio_proc_id) != noErr) return;
	AudioDeviceStart(device, audio_proc_id);
#  else
	if (AudioDeviceAddIOProc(device, audio_cb, (void *)this) != noErr) return;
	AudioDeviceStart(device, audio_cb);
#  endif

	sample_size = (int)format.mSampleRate;

#elif defined(WIN32)
	WAVEFORMATEX	format;

	memset(&format, 0, sizeof(format));
	format.cbSize          = sizeof(format);
	format.wFormatTag      = WAVE_FORMAT_PCM;
	format.nChannels       = 2;
	format.nSamplesPerSec  = 44100;
	format.nAvgBytesPerSec = 44100 * 4;
	format.nBlockAlign     = 4;
	format.wBitsPerSample  = 16;

	data_handle = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE, format.nSamplesPerSec * 4);
	if (!data_handle) return;

	data_ptr = (LPSTR)GlobalLock(data_handle);

	header_handle = GlobalAlloc(GMEM_MOVEABLE | GMEM_SHARE, sizeof(WAVEHDR));
	if (!header_handle) return;

	header_ptr = (WAVEHDR *)GlobalLock(header_handle);

	header_ptr->lpData  = data_ptr;
	header_ptr->dwFlags = 0;
	header_ptr->dwLoops = 0;

	if (waveOutOpen(&device, WAVE_MAPPER, &format, 0, 0, WAVE_ALLOWSYNC)
			!= MMSYSERR_NOERROR) return;

	sample_size = format.nSamplesPerSec;

#else
#  ifdef HAVE_ALSA_ASOUNDLIB_H
	handle = NULL;

	if (snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0) >= 0) {
		// Initialize PCM sound stuff...
		snd_pcm_hw_params_t *params;

		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);
		snd_pcm_hw_params_set_channels(handle, params, 2);
		unsigned rate = 44100;
		int dir;
		snd_pcm_hw_params_set_rate_near(handle, params, &rate, &dir);
		snd_pcm_uframes_t period = (int)rate;
		snd_pcm_hw_params_set_period_size_near(handle, params, &period, &dir);

		sample_size = rate;

		if (snd_pcm_hw_params(handle, params) < 0) {
			sample_size = 0;
			snd_pcm_close(handle);
			handle = NULL;
		}
	}
#  endif // HAVE_ALSA_ASOUNDLIB_H
#endif // __APPLE__

	if (sample_size) {
//.........这里部分代码省略.........

int Aisound::Open_Pcm()
{
	BEGINFUNC_USING_BY_VOICE
	int err;
	int dir;
	int size;
	char *buffer;
	unsigned int val;
	snd_pcm_uframes_t frames;
	snd_pcm_hw_params_t* params;
	int channels = 0;
	if ( (err = snd_pcm_open(&handle, "plug:cmd", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
	{
		dbug_out("cannot open audio device (%s)\n", snd_strerror (err));
		goto OpenPcmFail;
	}
	dbug_out("After snd_pcm_open for SND_PCM_STREAM_PLAYBACK");
	
	snd_pcm_hw_params_alloca(&params);//为�数��分�空间
	
	if( (err = snd_pcm_hw_params_any(handle, params)) < 0)//�数�始化
	{
		dbug_out("snd_pcm_hw_params_any failed!	 err = %d\n", err);
		goto OpenPcmFail;
	}
	if( (err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)//设置为交错模�
	{
		dbug_out("snd_pcm_hw_params_set_access failed!	 err = %d\n", err);
		goto OpenPcmFail;
	}
	if( (err = snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE)) < 0)//使用16�样本
	{
		dbug_out("snd_pcm_hw_params_set_format failed!	 err = %d\n", err);
		goto OpenPcmFail;
	}
	channels = val = 1;
	if( (err = snd_pcm_hw_params_set_channels(handle, params, val)) < 0)//设置为立体声
	{
		dbug_out("snd_pcm_hw_params_set_channels failed!	 err = %d\n", err);
		goto OpenPcmFail;
	}
	val = 16000;
	if( (err = snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir)) < 0)//设置采样率为44.1KHz
	{
		dbug_out("snd_pcm_hw_params_set_rate_near failed!   err = %d\n", err);
		goto OpenPcmFail;
	}


#if 1
	frames = 32;
	if( (err = snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir)) < 0)
	{
		dbug_out("snd_pcm_hw_params_set_period_size_near failed!	err = %d\n", err);
		goto OpenPcmFail;
	}
	if ( (err = snd_pcm_hw_params(handle, params)) < 0)
	{
		dbug_out("snd_pcm_hw_params-failed!	err = %d err: %s\n", err, snd_strerror(err));
		goto OpenPcmFail;
	}
	if( (err = snd_pcm_hw_params_get_period_size(params, &frames, &dir)) < 0)
	{
		dbug_out("snd_pcm_hw_params_get_period_size failed!	 err = %d\n", err);
		goto OpenPcmFail;
	}
	size = frames * channels * 2;
	buffer = (char *)malloc(sizeof(char) * size);

	if( (err = snd_pcm_hw_params_get_period_time(params, &val, &dir)) < 0)
	{
		dbug_out("snd_pcm_hw_params_get_period_time failed!	err = %d\n", err);
		goto OpenPcmFail;
	}
	
	return 0;
	
OpenPcmFail:
	return -1;
#endif 
	ENDFUNC_USING_BY_VOICE
}

bool CAESinkALSA::InitializeHW(AEAudioFormat &format)
{
  snd_pcm_hw_params_t *hw_params;

  snd_pcm_hw_params_alloca(&hw_params);
  memset(hw_params, 0, snd_pcm_hw_params_sizeof());

  snd_pcm_hw_params_any(m_pcm, hw_params);
  snd_pcm_hw_params_set_access(m_pcm, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);

  unsigned int sampleRate   = format.m_sampleRate;
#if defined(HAS_AMLPLAYER) || defined(HAS_LIBAMCODEC)
  // alsa/kernel lies, so map everything to 44100 or 48000
  switch(sampleRate)
  {
    case 11025:
    case 22050:
    case 88200:
    case 176400:
      sampleRate = 44100;
      break;
    case 8000:
    case 16000:
    case 24000:
    case 32000:
    case 96000:
    case 192000:
    case 384000:
      sampleRate = 48000;
      break;
  }
#endif
  unsigned int channelCount = format.m_channelLayout.Count();
  snd_pcm_hw_params_set_rate_near    (m_pcm, hw_params, &sampleRate, NULL);
  snd_pcm_hw_params_set_channels_near(m_pcm, hw_params, &channelCount);

  /* ensure we opened X channels or more */
  if (format.m_channelLayout.Count() > channelCount)
  {
    CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Unable to open the required number of channels");
  }

  /* update the channelLayout to what we managed to open */
  format.m_channelLayout.Reset();
  for (unsigned int i = 0; i < channelCount; ++i)
    format.m_channelLayout += ALSAChannelMap[i];

  snd_pcm_format_t fmt = AEFormatToALSAFormat(format.m_dataFormat);
  if (fmt == SND_PCM_FORMAT_UNKNOWN)
  {
    /* if we dont support the requested format, fallback to float */
    format.m_dataFormat = AE_FMT_FLOAT;
    fmt                 = SND_PCM_FORMAT_FLOAT;
  }

  /* try the data format */
  if (snd_pcm_hw_params_set_format(m_pcm, hw_params, fmt) < 0)
  {
    /* if the chosen format is not supported, try each one in decending order */
    CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Your hardware does not support %s, trying other formats", CAEUtil::DataFormatToStr(format.m_dataFormat));
    for (enum AEDataFormat i = AE_FMT_MAX; i > AE_FMT_INVALID; i = (enum AEDataFormat)((int)i - 1))
    {
      if (AE_IS_RAW(i) || i == AE_FMT_MAX)
        continue;

      if (m_passthrough && i != AE_FMT_S16BE && i != AE_FMT_S16LE)
	continue;

      fmt = AEFormatToALSAFormat(i);

      if (fmt == SND_PCM_FORMAT_UNKNOWN || snd_pcm_hw_params_set_format(m_pcm, hw_params, fmt) < 0)
      {
        fmt = SND_PCM_FORMAT_UNKNOWN;
        continue;
      }

      int fmtBits = CAEUtil::DataFormatToBits(i);
      int bits    = snd_pcm_hw_params_get_sbits(hw_params);
      if (bits != fmtBits)
      {
        /* if we opened in 32bit and only have 24bits, pack into 24 */
        if (fmtBits == 32 && bits == 24)
          i = AE_FMT_S24NE4;
        else
          continue;
      }

      /* record that the format fell back to X */
      format.m_dataFormat = i;
      CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Using data format %s", CAEUtil::DataFormatToStr(format.m_dataFormat));
      break;
    }

    /* if we failed to find a valid output format */
    if (fmt == SND_PCM_FORMAT_UNKNOWN)
    {
      CLog::Log(LOGERROR, "CAESinkALSA::InitializeHW - Unable to find a suitable output format");
      return false;
    }
  }
//.........这里部分代码省略.........

int main()
{
    int rc;
    snd_pcm_t* handle;
    snd_pcm_hw_params_t* params;
    unsigned int val;
    unsigned int val2;
    int dir;
    snd_pcm_uframes_t frames;

    if ( (rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    {
        std::cerr << "unable to open pcm devices: " << snd_strerror(rc) << std::endl;
        exit(1);
    }

    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);

    val = 44100;

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

    if ( (rc = snd_pcm_hw_params(handle, params)) < 0)
    {
        std::cerr << "unable to set hw parameters: " << snd_strerror(rc) << std::endl;
        exit(1);
    }

    std::cout << "PCM handle name = " << snd_pcm_name(handle) << std::endl;

    std::cout << "PCM state = " << snd_pcm_state_name(snd_pcm_state(handle)) << std::endl;

    snd_pcm_hw_params_get_access(params, (snd_pcm_access_t *)&val);

    std::cout << "access type = " << snd_pcm_access_name((snd_pcm_access_t)val) << std::endl;

    snd_pcm_hw_params_get_format(params, (snd_pcm_format_t*)(&val));

    std::cout << "format = '" << snd_pcm_format_name((snd_pcm_format_t)val) << "' (" << snd_pcm_format_description((snd_pcm_format_t)val) << ")" << std::endl;

    snd_pcm_hw_params_get_subformat(params, (snd_pcm_subformat_t *)&val);
    std::cout << "subformat = '" <<
              snd_pcm_subformat_name((snd_pcm_subformat_t)val) << "' (" << snd_pcm_subformat_description((snd_pcm_subformat_t)val) << ")" << std::endl;

    snd_pcm_hw_params_get_channels(params, &val);
    std::cout << "channels = " << val << std::endl;

    snd_pcm_hw_params_get_rate(params, &val, &dir);
    std::cout << "rate = " << val << " bps" << std::endl;

    snd_pcm_hw_params_get_period_time(params, &val, &dir);
    std::cout << "period time = " << val << " us" << std::endl;

    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    std::cout << "period size = " << static_cast<int>(frames) << " frames" << std::endl;

    snd_pcm_hw_params_get_buffer_time(params, &val, &dir);
    std::cout << "buffer time = " << val << " us" << std::endl;

    snd_pcm_hw_params_get_buffer_size(params, (snd_pcm_uframes_t *) &val);
    std::cout << "buffer size = " << val << " frames" << std::endl;

    snd_pcm_hw_params_get_periods(params, &val, &dir);
    std::cout << "periods per buffer = " << val << " frames" << std::endl;

    snd_pcm_hw_params_get_rate_numden(params, &val, &val2);
    std::cout << "exact rate = " << val/val2 << " bps" << std::endl;

    val = snd_pcm_hw_params_get_sbits(params);
    std::cout << "significant bits = " << val << std::endl;

    snd_pcm_hw_params_get_tick_time(params, &val, &dir);
    std::cout << "tick time = " << val << " us" << std::endl;

    val = snd_pcm_hw_params_is_batch(params);
    std::cout << "is batch = " << val << std::endl;

    val = snd_pcm_hw_params_is_block_transfer(params);
    std::cout << "is block transfer = " << val << std::endl;

    val = snd_pcm_hw_params_is_double(params);
    std::cout << "is double = " << val << std::endl;

    val = snd_pcm_hw_params_is_half_duplex(params);
    std::cout << "is half duplex = " << val << std::endl;

    val = snd_pcm_hw_params_is_joint_duplex(params);
    std::cout << "is joint duplex = " << val << std::endl;

    val = snd_pcm_hw_params_can_overrange(params);
    std::cout << "can overrange = " << val << std::endl;

//.........这里部分代码省略.........

bool ALSAWriter::processParams(bool *paramsCorrected)
{
	const unsigned chn = getParam("chn").toUInt();
	const unsigned rate = getParam("rate").toUInt();
	const bool resetAudio = channels != chn || sample_rate != rate;
	channels = chn;
	sample_rate = rate;
	if (resetAudio || err)
	{
		snd_pcm_hw_params_t *params;
		snd_pcm_hw_params_alloca(&params);

		close();

		QString chosenDevName = devName;
		if (autoFindMultichannelDevice && channels > 2)
		{
			bool mustAutoFind = true, forceStereo = false;
			if (!snd_pcm_open(&snd, chosenDevName.toLocal8Bit(), SND_PCM_STREAM_PLAYBACK, 0))
			{
				if (snd_pcm_type(snd) == SND_PCM_TYPE_HW)
				{
					unsigned max_chn = 0;
					snd_pcm_hw_params_any(snd, params);
					mustAutoFind = snd_pcm_hw_params_get_channels_max(params, &max_chn) || max_chn < channels;
				}
#ifdef HAVE_CHMAP
				else if (paramsCorrected)
				{
					snd_pcm_chmap_query_t **chmaps = snd_pcm_query_chmaps(snd);
					if (chmaps)
						snd_pcm_free_chmaps(chmaps);
					else
						forceStereo = true;
				}
#endif
				snd_pcm_close(snd);
				snd = nullptr;
			}
			if (mustAutoFind)
			{
				QString newDevName;
				if (channels <= 4)
					newDevName = "surround40";
				else if (channels <= 6)
					newDevName = "surround51";
				else
					newDevName = "surround71";
				if (!newDevName.isEmpty() && newDevName != chosenDevName)
				{
					if (ALSACommon::getDevices().first.contains(newDevName))
						chosenDevName = newDevName;
					else if (forceStereo)
					{
						channels = 2;
						*paramsCorrected = true;
					}
				}
			}
		}
		if (!chosenDevName.isEmpty())
		{
			bool sndOpen = !snd_pcm_open(&snd, chosenDevName.toLocal8Bit(), SND_PCM_STREAM_PLAYBACK, 0);
			if (devName != chosenDevName)
			{
				if (sndOpen)
					QMPlay2Core.logInfo("ALSA :: " + devName + "\" -> \"" + chosenDevName + "\"");
				else
				{
					sndOpen = !snd_pcm_open(&snd, devName.toLocal8Bit(), SND_PCM_STREAM_PLAYBACK, 0);
					QMPlay2Core.logInfo("ALSA :: " + tr("Cannot open") + " \"" + chosenDevName + "\", " + tr("back to") + " \"" + devName + "\"");
				}
			}
			if (sndOpen)
			{
				snd_pcm_hw_params_any(snd, params);

				snd_pcm_format_t fmt = SND_PCM_FORMAT_UNKNOWN;
				if (!snd_pcm_hw_params_test_format(snd, params, SND_PCM_FORMAT_S32))
				{
					fmt = SND_PCM_FORMAT_S32;
					sample_size = 4;
				}
				else if (!snd_pcm_hw_params_test_format(snd, params, SND_PCM_FORMAT_S16))
				{
					fmt = SND_PCM_FORMAT_S16;
					sample_size = 2;
				}
				else if (!snd_pcm_hw_params_test_format(snd, params, SND_PCM_FORMAT_S8))
				{
					fmt = SND_PCM_FORMAT_S8;
					sample_size = 1;
				}

				unsigned delay_us = round(delay * 1000000.0);
				if (fmt != SND_PCM_FORMAT_UNKNOWN && set_snd_pcm_hw_params(snd, params, fmt, channels, sample_rate, delay_us))
				{
					bool err2 = false;
					if (channels != chn || sample_rate != rate)
					{
//.........这里部分代码省略.........

void play(int sec, int freq, char *file)
{
	long loops;
	int rc;
	int size;
	snd_pcm_t *handle;
	snd_pcm_hw_params_t *params;
	unsigned int val;
	int dir;
	snd_pcm_uframes_t frames;
	char *buffer;
	int fd;

	/* Check ranges */
	if (sec < 1 || sec > 4000) {
		printf("WARNING: Incorrect time to play range [1,4000] s\n");
		printf("\tSetting time to play to 5s...\n");
		sec = 5;
	}
	if (freq < 1000 || freq > 100000) {
		printf("ERROR: Incorrect frequency range [1000,100000] Hz\n");
		printf("\tSetting frequency to 44.1 kHz...\n");
		freq = 44100;
	}

	/* Open file */
	fd = open(file, O_RDONLY);
	if (fd < 0) {
		/* There was an error opening the file */
		printf("ERROR: Couldn't open file to play\n");
		printf("\tPlease make sure file exists\n");
	} else {
		/* Print that the file is playing with its parameters */
		printf("Playing file %s for %d seconds", file, sec);
		printf(" and frequency %d...\n", freq);

		/* Open PCM device for playback */
		rc = snd_pcm_open(&handle, "default", 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 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, 2);
		/* freq bits/second sampling rate (CD quality) */
		val = freq;
		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 * 4; /* 2 bytes/sample, 2 channels */
		buffer = (char *) malloc(size);
		/* We want to loop for sec seconds */
		snd_pcm_hw_params_get_period_time(params, &val, &dir);
		/* sec seconds in microseconds divided by period time */
		loops = sec*1000000 / val;

		while (loops > 0) {
			loops--;
			rc = read(fd, buffer, size);
			if (rc == 0) {
				fprintf(stderr, "end of file on input\n");
				break;
			} else if (rc != size) {
				fprintf(stderr, "short read: read %d bytes\n",
					rc);
			}
			rc = snd_pcm_writei(handle, buffer, frames);
			if (rc == -EPIPE) {
				/* EPIPE means underrun */
				fprintf(stderr, "underrun occurred\n");
				snd_pcm_prepare(handle);
			} else if (rc < 0) {
//.........这里部分代码省略.........

Error AudioDriverALSA::init() {

	active=false;
	thread_exited=false;
	exit_thread=false;
	pcm_open = false;
	samples_in = NULL;
	samples_out = NULL;

	mix_rate = GLOBAL_DEF("audio/mix_rate",44100);
	output_format = OUTPUT_STEREO;
	channels = 2;


	int                  status;
	snd_pcm_hw_params_t *hwparams;
	snd_pcm_sw_params_t *swparams;

#define CHECK_FAIL(m_cond)\
	if (m_cond) {\
		fprintf(stderr,"ALSA ERR: %s\n",snd_strerror(status));\
		snd_pcm_close(pcm_handle);\
		ERR_FAIL_COND_V(m_cond,ERR_CANT_OPEN);\
	}

	//todo, add
	//6 chans - "plug:surround51"
	//4 chans - "plug:surround40";

	status = snd_pcm_open(&pcm_handle, "default", SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);

	ERR_FAIL_COND_V( status<0, ERR_CANT_OPEN );

	snd_pcm_hw_params_alloca(&hwparams);

	status = snd_pcm_hw_params_any(pcm_handle, hwparams);
	CHECK_FAIL( status<0 );

	status = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
	CHECK_FAIL( status<0 );

	//not interested in anything else
	status = snd_pcm_hw_params_set_format(pcm_handle, hwparams, SND_PCM_FORMAT_S16_LE);
	CHECK_FAIL( status<0 );

	//todo: support 4 and 6
	status = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, 2);
	CHECK_FAIL( status<0 );

	status = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &mix_rate, NULL);
	CHECK_FAIL( status<0 );

	int latency = GLOBAL_DEF("audio/output_latency",25);
	buffer_size = nearest_power_of_2( latency * mix_rate / 1000 );

	// set buffer size from project settings
	status = snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hwparams, &buffer_size);
	CHECK_FAIL( status<0 );

	// make period size 1/8 
	period_size = buffer_size >> 3;
	status = snd_pcm_hw_params_set_period_size_near(pcm_handle, hwparams, &period_size, NULL);
	CHECK_FAIL( status<0 );

	unsigned int periods=2;
	status = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &periods, NULL);
	CHECK_FAIL( status<0 );

	status = snd_pcm_hw_params(pcm_handle,hwparams);
	CHECK_FAIL( status<0 );

	//snd_pcm_hw_params_free(&hwparams);


	snd_pcm_sw_params_alloca(&swparams);

	status = snd_pcm_sw_params_current(pcm_handle, swparams);
	CHECK_FAIL( status<0 );

	status = snd_pcm_sw_params_set_avail_min(pcm_handle, swparams, period_size);
	CHECK_FAIL( status<0 );

	status = snd_pcm_sw_params_set_start_threshold(pcm_handle, swparams, 1);
	CHECK_FAIL( status<0 );

	status = snd_pcm_sw_params(pcm_handle, swparams);
	CHECK_FAIL( status<0 );

	samples_in = memnew_arr(int32_t, period_size*channels);
	samples_out = memnew_arr(int16_t, period_size*channels);

	snd_pcm_nonblock(pcm_handle, 0);

	mutex=Mutex::create();
	thread = Thread::create(AudioDriverALSA::thread_func, this);

	return OK;
};

static int init_audio_device(common_data_t *p_common_data)
{
	int ret;
	int dir = 0;
	unsigned int val;
	snd_pcm_hw_params_t *p_params;
	snd_pcm_uframes_t buffer_size;
	unsigned int buffer_time;
	unsigned int period_time;
	snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
	size_t bits_per_sample;
	size_t bits_per_frame;

	ret = snd_pcm_open(&p_common_data->handle, "plughw:0,0", SND_PCM_STREAM_PLAYBACK, 0);
	if (ret < 0) { 
		dbg_alsa("unable to open pcm device: %s\n", snd_strerror(ret));
		return -1;
	}

	snd_pcm_hw_params_alloca(&p_params);

	snd_pcm_hw_params_any(p_common_data->handle, p_params);

	snd_pcm_hw_params_set_access(p_common_data->handle, p_params, SND_PCM_ACCESS_RW_INTERLEAVED);

	snd_pcm_hw_params_set_format(p_common_data->handle, p_params, SND_PCM_FORMAT_S16_LE);

	snd_pcm_hw_params_set_channels(p_common_data->handle, p_params, 2);

	val = 44100;
	snd_pcm_hw_params_set_rate_near(p_common_data->handle, p_params, &val, &dir);




	snd_pcm_hw_params_get_buffer_time_max(p_params, &buffer_time, 0);

//	if (buffer_time > 500000)
//		buffer_time = 500000;
//
//	period_time = buffer_time / 4;
//
//	snd_pcm_hw_params_set_period_time_near(p_common_data->handle, p_params, &period_time, 0);
//	snd_pcm_hw_params_set_buffer_time_near(p_common_data->handle, p_params, &buffer_time, 0);

	p_common_data->period_size = 2048;
	snd_pcm_hw_params_set_period_size_near(p_common_data->handle, p_params, &p_common_data->period_size, &dir);

	ret = snd_pcm_hw_params(p_common_data->handle, p_params);
	if (ret < 0){ 
		dbg_alsa("unable to set hw parameters: %s\n", snd_strerror(ret));
		exit(1);
	}
	
	ret = snd_pcm_state(p_common_data->handle);
	dbg("state is %d\n", ret);
	snd_pcm_hw_params_get_period_size(p_params, &p_common_data->period_size, &dir);
	snd_pcm_hw_params_get_buffer_size(p_params, &buffer_size);

	if (p_common_data->period_size == buffer_size) {
		dbg_alsa("Can't use period size equal to buffer size (%lu == %lu)\n", p_common_data->period_size, buffer_size);
	}

	dbg("period size is : %lu frames\n", p_common_data->period_size);
	dbg("buffer size is : %lu frames\n", buffer_size);

	bits_per_sample = snd_pcm_format_physical_width(format);
	bits_per_frame = bits_per_sample * 2;
	p_common_data->chunk_bytes = p_common_data->period_size * bits_per_frame / 8;

	//g_buf = (msg_t *)malloc(sizeof(msg_t)+(char)p_common_data->chunk_bytes);

	dbg("sample rate is %d\n", val);
	dbg("bits_per_sample %d\n", bits_per_sample);
	dbg("bits_per_frame %d\n", bits_per_frame);
	dbg("chunk_bytes %d\n", p_common_data->chunk_bytes);
	dbg("PCM handle name = '%s'\n",snd_pcm_name(p_common_data->handle));

	return 0;
}

bool CAESinkALSA::InitializeHW(AEAudioFormat &format)
{
  snd_pcm_hw_params_t *hw_params;

  snd_pcm_hw_params_alloca(&hw_params);
  memset(hw_params, 0, snd_pcm_hw_params_sizeof());

  snd_pcm_hw_params_any(m_pcm, hw_params);
  snd_pcm_hw_params_set_access(m_pcm, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);

  unsigned int sampleRate   = format.m_sampleRate;
  unsigned int channelCount = format.m_channelLayout.Count();
  snd_pcm_hw_params_set_rate_near    (m_pcm, hw_params, &sampleRate, NULL);
  snd_pcm_hw_params_set_channels_near(m_pcm, hw_params, &channelCount);

  /* ensure we opened X channels or more */
  if (format.m_channelLayout.Count() > channelCount)
  {
    CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Unable to open the required number of channels");
  }

  /* update the channelLayout to what we managed to open */
  format.m_channelLayout.Reset();
  for (unsigned int i = 0; i < channelCount; ++i)
    format.m_channelLayout += ALSAChannelMap[i];

  snd_pcm_format_t fmt = AEFormatToALSAFormat(format.m_dataFormat);
  if (fmt == SND_PCM_FORMAT_UNKNOWN)
  {
    /* if we dont support the requested format, fallback to float */
    format.m_dataFormat = AE_FMT_FLOAT;
    fmt                 = SND_PCM_FORMAT_FLOAT;
  }

  /* try the data format */
  if (snd_pcm_hw_params_set_format(m_pcm, hw_params, fmt) < 0)
  {
    /* if the chosen format is not supported, try each one in decending order */
    CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Your hardware does not support %s, trying other formats", CAEUtil::DataFormatToStr(format.m_dataFormat));
    for (enum AEDataFormat i = AE_FMT_MAX; i > AE_FMT_INVALID; i = (enum AEDataFormat)((int)i - 1))
    {
      if (AE_IS_RAW(i) || i == AE_FMT_MAX)
        continue;

      if (m_passthrough && i != AE_FMT_S16BE && i != AE_FMT_S16LE)
	continue;

      fmt = AEFormatToALSAFormat(i);

      if (fmt == SND_PCM_FORMAT_UNKNOWN || snd_pcm_hw_params_set_format(m_pcm, hw_params, fmt) < 0)
      {
        fmt = SND_PCM_FORMAT_UNKNOWN;
        continue;
      }

      int fmtBits = CAEUtil::DataFormatToBits(i);
      int bits    = snd_pcm_hw_params_get_sbits(hw_params);
      if (bits != fmtBits)
      {
        /* if we opened in 32bit and only have 24bits, pack into 24 */
        if (fmtBits == 32 && bits == 24)
          i = AE_FMT_S24NE4;
        else
          continue;
      }

      /* record that the format fell back to X */
      format.m_dataFormat = i;
      CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Using data format %s", CAEUtil::DataFormatToStr(format.m_dataFormat));
      break;
    }

    /* if we failed to find a valid output format */
    if (fmt == SND_PCM_FORMAT_UNKNOWN)
    {
      CLog::Log(LOGERROR, "CAESinkALSA::InitializeHW - Unable to find a suitable output format");
      return false;
    }
  }

  unsigned int periods;

  snd_pcm_uframes_t periodSize, bufferSize;
  snd_pcm_hw_params_get_buffer_size_max(hw_params, &bufferSize);

  bufferSize  = std::min(bufferSize, (snd_pcm_uframes_t)8192);
  periodSize  = bufferSize / ALSA_PERIODS;
  periods     = ALSA_PERIODS;

  CLog::Log(LOGDEBUG, "CAESinkALSA::InitializeHW - Request: periodSize %lu, periods %u, bufferSize %lu", periodSize, periods, bufferSize);

  /* work on a copy of the hw params */
  snd_pcm_hw_params_t *hw_params_copy;
  snd_pcm_hw_params_alloca(&hw_params_copy);

  /* try to set the buffer size then the period size */
  snd_pcm_hw_params_copy(hw_params_copy, hw_params);
  snd_pcm_hw_params_set_buffer_size_near(m_pcm, hw_params_copy, &bufferSize);
  snd_pcm_hw_params_set_period_size_near(m_pcm, hw_params_copy, &periodSize, NULL);
  snd_pcm_hw_params_set_periods_near    (m_pcm, hw_params_copy, &periods   , NULL);
//.........这里部分代码省略.........

/* Initialise audio devices. */
int digi_init()
{
 int err, tmp;
 char *device = "plughw:0,0";
 snd_pcm_hw_params_t *params;
 pthread_attr_t attr;
 pthread_mutexattr_t mutexattr;

 //added on 980905 by adb to init sound kill system
 memset(SampleHandles, 255, sizeof(SampleHandles));
 //end edit by adb

 /* Open the ALSA sound device */
 if ((err = snd_pcm_open(&snd_devhandle,device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {  
     con_printf(CON_CRITICAL, "open failed: %s\n", snd_strerror( err ));  
     return -1; 
 } 

 snd_pcm_hw_params_alloca(&params);
 err = snd_pcm_hw_params_any(snd_devhandle, params);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }
 err = snd_pcm_hw_params_set_access(snd_devhandle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }
 err = snd_pcm_hw_params_set_format(snd_devhandle, params, SND_PCM_FORMAT_U8);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }
 err = snd_pcm_hw_params_set_channels(snd_devhandle, params, 2);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }
 tmp = 11025;
 err = snd_pcm_hw_params_set_rate_near(snd_devhandle, params, &tmp, NULL);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }
 snd_pcm_hw_params_set_periods(snd_devhandle, params, 3, 0);
 snd_pcm_hw_params_set_buffer_size(snd_devhandle,params, (SOUND_BUFFER_SIZE*3)/2);

 err = snd_pcm_hw_params(snd_devhandle, params);
 if (err < 0) {
     con_printf(CON_CRITICAL,"ALSA: Error %s\n", snd_strerror(err));
     return -1;
 }

 /* Start the mixer thread */

 /* We really should check the results of these */
 pthread_mutexattr_init(&mutexattr);
 pthread_mutex_init(&mutex,&mutexattr);
 pthread_mutexattr_destroy(&mutexattr);
 
 if (pthread_attr_init(&attr) != 0) {
  con_printf(CON_CRITICAL, "failed to init attr\n");
  snd_pcm_close( snd_devhandle ); 
  return -1;
 }

 pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

 pthread_create(&thread_id,&attr,mixer_thread,NULL);
 pthread_attr_destroy(&attr);

 digi_initialised = 1;
 return 0;
}

void
ags_devout_alsa_init(AgsDevout *devout,
		     GError **error)
{
  static unsigned int period_time = 100000;
  static snd_pcm_format_t format = SND_PCM_FORMAT_S16;

  int rc;
  snd_pcm_t *handle;
  snd_pcm_hw_params_t *hwparams;
  unsigned int val;
  snd_pcm_uframes_t frames;
  unsigned int rate;
  unsigned int rrate;
  unsigned int channels;
  snd_pcm_uframes_t size;
  snd_pcm_sframes_t buffer_size;
  snd_pcm_sframes_t period_size;
  snd_pcm_sw_params_t *swparams;
  int period_event = 0;
  int err, dir;

  /* Open PCM device for playback. */
  if ((err = snd_pcm_open(&handle, devout->out.alsa.device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
    printf("Playback open error: %s\n", snd_strerror(err));
    return;
  }

  snd_pcm_hw_params_alloca(&hwparams);
  snd_pcm_sw_params_alloca(&swparams);

  /* choose all parameters */
  err = snd_pcm_hw_params_any(handle, hwparams);
  if (err < 0) {
    printf("Broken configuration for playback: no configurations available: %s\n", snd_strerror(err));
    return;
  }

  /* set hardware resampling */
  err = snd_pcm_hw_params_set_rate_resample(handle, hwparams, 1);
  if (err < 0) {
    printf("Resampling setup failed for playback: %s\n", snd_strerror(err));
    return;
  }

  /* set the interleaved read/write format */
  err = snd_pcm_hw_params_set_access(handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
  if (err < 0) {
    printf("Access type not available for playback: %s\n", snd_strerror(err));
    return;
  }

  /* set the sample format */
  err = snd_pcm_hw_params_set_format(handle, hwparams, format);
  if (err < 0) {
    printf("Sample format not available for playback: %s\n", snd_strerror(err));
    return;
  }

  /* set the count of channels */
  channels = devout->dsp_channels;
  err = snd_pcm_hw_params_set_channels(handle, hwparams, channels);
  if (err < 0) {
    printf("Channels count (%i) not available for playbacks: %s\n", channels, snd_strerror(err));
    return;
  }

  /* set the stream rate */
  rate = devout->frequency;
  rrate = rate;
  err = snd_pcm_hw_params_set_rate_near(handle, hwparams, &rrate, 0);
  if (err < 0) {
    printf("Rate %iHz not available for playback: %s\n", rate, snd_strerror(err));
    return;
  }

  if (rrate != rate) {
    printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);
    exit(-EINVAL);
  }

  /* set the buffer size */
  size = devout->buffer_size;
  err = snd_pcm_hw_params_set_buffer_size(handle, hwparams, size);
  if (err < 0) {
    printf("Unable to set buffer size %i for playback: %s\n", size, snd_strerror(err));
    return;
  }

  buffer_size = size;

  /* set the period time */
  err = snd_pcm_hw_params_set_period_time_near(handle, hwparams, &period_time, &dir);
  if (err < 0) {
    printf("Unable to set period time %i for playback: %s\n", period_time, snd_strerror(err));
    return;
  }

  err = snd_pcm_hw_params_get_period_size(hwparams, &size, &dir);
  if (err < 0) {
//.........这里部分代码省略.........

void
ags_devout_pcm_info(char *card_id,
		    guint *channels_min, guint *channels_max,
		    guint *rate_min, guint *rate_max,
		    guint *buffer_size_min, guint *buffer_size_max,
		    GError **error)
{
  int rc;
  snd_pcm_t *handle;
  snd_pcm_hw_params_t *params;
  unsigned int val;
  int dir;
  snd_pcm_uframes_t frames;
  int err;

  /* Open PCM device for playback. */
  handle = NULL;

  rc = snd_pcm_open(&handle, card_id, SND_PCM_STREAM_PLAYBACK, 0);

  if(rc < 0) {
    g_message("unable to open pcm device: %s\n\0", snd_strerror(rc));

    g_set_error(error,
		AGS_DEVOUT_ERROR,
		AGS_DEVOUT_ERROR_LOCKED_SOUNDCARD,
		"unable to open pcm device: %s\n\0",
		snd_strerror(rc));

    return;
  }

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

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

  /* channels */
  snd_pcm_hw_params_get_channels_min(params, &val);
  *channels_min = val;

  snd_pcm_hw_params_get_channels_max(params, &val);
  *channels_max = val;

  /* samplerate */
  dir = 0;
  snd_pcm_hw_params_get_rate_min(params, &val, &dir);
  *rate_min = val;

  dir = 0;
  snd_pcm_hw_params_get_rate_max(params, &val, &dir);
  *rate_max = val;

  /* buffer size */
  dir = 0;
  snd_pcm_hw_params_get_buffer_size_min(params, &frames);
  *buffer_size_min = frames;

  dir = 0;
  snd_pcm_hw_params_get_buffer_size_max(params, &frames);
  *buffer_size_max = frames;

  snd_pcm_close(handle);
}

    /**
     * Create and initialize Alsa audio output device with given parameters.
     *
     * @param Parameters - optional parameters
     * @throws AudioOutputException  if output device cannot be opened
     */
    AudioOutputDeviceAlsa::AudioOutputDeviceAlsa(std::map<String,DeviceCreationParameter*> Parameters) : AudioOutputDevice(Parameters), Thread(true, true, 1, 0) {
        pcm_handle           = NULL;
        stream               = SND_PCM_STREAM_PLAYBACK;
        this->uiAlsaChannels = ((DeviceCreationParameterInt*)Parameters["CHANNELS"])->ValueAsInt();
        this->uiSamplerate   = ((DeviceCreationParameterInt*)Parameters["SAMPLERATE"])->ValueAsInt();
        this->FragmentSize   = ((DeviceCreationParameterInt*)Parameters["FRAGMENTSIZE"])->ValueAsInt();
        uint Fragments       = ((DeviceCreationParameterInt*)Parameters["FRAGMENTS"])->ValueAsInt();
        String Card          = ((DeviceCreationParameterString*)Parameters["CARD"])->ValueAsString();

        dmsg(2,("Checking if hw parameters supported...\n"));
        if (HardwareParametersSupported(Card, uiAlsaChannels, uiSamplerate, Fragments, FragmentSize)) {
            pcm_name = "hw:" + Card;
        }
        else {
            fprintf(stderr, "Warning: your soundcard doesn't support chosen hardware parameters; ");
            fprintf(stderr, "trying to compensate support lack with plughw...");
            fflush(stdout);
            pcm_name = "plughw:" + Card;
        }
        dmsg(2,("HW check completed.\n"));

        int err;

        snd_pcm_hw_params_alloca(&hwparams);  // Allocate the snd_pcm_hw_params_t structure on the stack.

        /* Open PCM. The last parameter of this function is the mode. */
        /* If this is set to 0, the standard mode is used. Possible   */
        /* other values are SND_PCM_NONBLOCK and SND_PCM_ASYNC.       */
        /* If SND_PCM_NONBLOCK is used, read / write access to the    */
        /* PCM device will return immediately. If SND_PCM_ASYNC is    */
        /* specified, SIGIO will be emitted whenever a period has     */
        /* been completely processed by the soundcard.                */
        if ((err = snd_pcm_open(&pcm_handle, pcm_name.c_str(), stream, 0)) < 0) {
            throw AudioOutputException(String("Error opening PCM device ") + pcm_name + ": " + snd_strerror(err));
        }

        if ((err = snd_pcm_hw_params_any(pcm_handle, hwparams)) < 0) {
            throw AudioOutputException(String("Error, cannot initialize hardware parameter structure: ") + snd_strerror(err));
        }

        /* Set access type. This can be either    */
        /* SND_PCM_ACCESS_RW_INTERLEAVED or       */
        /* SND_PCM_ACCESS_RW_NONINTERLEAVED.      */
        if ((err = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
            throw AudioOutputException(String("Error snd_pcm_hw_params_set_access: ") + snd_strerror(err));
        }

        /* Set sample format */
        #if WORDS_BIGENDIAN
        if ((err = snd_pcm_hw_params_set_format(pcm_handle, hwparams, SND_PCM_FORMAT_S16_BE)) < 0)
        #else // little endian
        if ((err = snd_pcm_hw_params_set_format(pcm_handle, hwparams, SND_PCM_FORMAT_S16_LE)) < 0)
        #endif
        {
            throw AudioOutputException(String("Error setting sample format: ") + snd_strerror(err));
        }

        int dir = 0;

        /* Set sample rate. If the exact rate is not supported */
        /* by the hardware, use nearest possible rate.         */
        #if ALSA_MAJOR > 0
        if((err = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &uiSamplerate, &dir)) < 0)
        #else
        if((err = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, uiSamplerate, &dir)) < 0)
        #endif
        {
            throw AudioOutputException(String("Error setting sample rate: ") + snd_strerror(err));
        }

        if ((err = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, uiAlsaChannels)) < 0) {
            throw AudioOutputException(String("Error setting number of channels: ") + snd_strerror(err));
        }

        /* Set number of periods. Periods used to be called fragments. */
        if ((err = snd_pcm_hw_params_set_periods(pcm_handle, hwparams, Fragments, dir)) < 0) {
            throw AudioOutputException(String("Error setting number of periods: ") + snd_strerror(err));
        }

        /* Set buffer size (in frames). The resulting latency is given by */
        /* latency = periodsize * periods / (rate * bytes_per_frame)     */
        if ((err = snd_pcm_hw_params_set_buffer_size(pcm_handle, hwparams, (FragmentSize * Fragments))) < 0) {
            throw AudioOutputException(String("Error setting buffersize: ") + snd_strerror(err));
        }

        /* Apply HW parameter settings to */
        /* PCM device and prepare device  */
        if ((err = snd_pcm_hw_params(pcm_handle, hwparams)) < 0) {
            throw AudioOutputException(String("Error setting HW params: ") + snd_strerror(err));
        }

        if (snd_pcm_sw_params_malloc(&swparams) != 0) {
            throw AudioOutputException(String("Error in snd_pcm_sw_params_malloc: ") + snd_strerror(err));
        }
//.........这里部分代码省略.........

bool QAlsaAudioDeviceInfo::testSettings(const QAudioFormat& format) const
{
    // Set nearest to closest settings that do work.
    // See if what is in settings will work (return value).
    int err = -1;
    snd_pcm_t* pcmHandle;
    snd_pcm_hw_params_t *params;
    QString dev;

#if(SND_LIB_MAJOR == 1 && SND_LIB_MINOR == 0 && SND_LIB_SUBMINOR >= 14)
    dev = device;
    if (dev.compare(QLatin1String("default")) == 0) {
        QList<QByteArray> devices = availableDevices(QAudio::AudioOutput);
        if (!devices.isEmpty())
            dev = QLatin1String(devices.first().constData());
    }
#else
    if (dev.compare(QLatin1String("default")) == 0) {
        dev = QLatin1String("hw:0,0");
    } else {
        int idx = 0;
        char *name;

        QString shortName = device.mid(device.indexOf(QLatin1String("="),0)+1);

        while(snd_card_get_name(idx,&name) == 0) {
            if(shortName.compare(QLatin1String(name)) == 0)
                break;
            idx++;
        }
        dev = QString(QLatin1String("hw:%1,0")).arg(idx);
    }
#endif

    snd_pcm_stream_t stream = mode == QAudio::AudioOutput
                            ? SND_PCM_STREAM_PLAYBACK : SND_PCM_STREAM_CAPTURE;

    if (snd_pcm_open(&pcmHandle, dev.toLocal8Bit().constData(), stream, 0) < 0)
        return false;

    snd_pcm_nonblock(pcmHandle, 0);
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(pcmHandle, params);

    // set the values!
    snd_pcm_hw_params_set_channels(pcmHandle, params, format.channelCount());
    snd_pcm_hw_params_set_rate(pcmHandle, params, format.sampleRate(), 0);

    snd_pcm_format_t pcmFormat = SND_PCM_FORMAT_UNKNOWN;
    switch (format.sampleSize()) {
    case 8:
        if (format.sampleType() == QAudioFormat::SignedInt)
            pcmFormat = SND_PCM_FORMAT_S8;
        else if (format.sampleType() == QAudioFormat::UnSignedInt)
            pcmFormat = SND_PCM_FORMAT_U8;
        break;
    case 16:
        if (format.sampleType() == QAudioFormat::SignedInt) {
            pcmFormat = format.byteOrder() == QAudioFormat::LittleEndian
                      ? SND_PCM_FORMAT_S16_LE : SND_PCM_FORMAT_S16_BE;
        } else if (format.sampleType() == QAudioFormat::UnSignedInt) {
            pcmFormat = format.byteOrder() == QAudioFormat::LittleEndian
                      ? SND_PCM_FORMAT_U16_LE : SND_PCM_FORMAT_U16_BE;
        }
        break;
    case 32:
        if (format.sampleType() == QAudioFormat::SignedInt) {
            pcmFormat = format.byteOrder() == QAudioFormat::LittleEndian
                      ? SND_PCM_FORMAT_S32_LE : SND_PCM_FORMAT_S32_BE;
        } else if (format.sampleType() == QAudioFormat::UnSignedInt) {
            pcmFormat = format.byteOrder() == QAudioFormat::LittleEndian
                      ? SND_PCM_FORMAT_U32_LE : SND_PCM_FORMAT_U32_BE;
        } else if (format.sampleType() == QAudioFormat::Float) {
            pcmFormat = format.byteOrder() == QAudioFormat::LittleEndian
                      ? SND_PCM_FORMAT_FLOAT_LE : SND_PCM_FORMAT_FLOAT_BE;
        }
    }

    if (pcmFormat != SND_PCM_FORMAT_UNKNOWN)
        err = snd_pcm_hw_params_set_format(pcmHandle, params, pcmFormat);

    // For now, just accept only audio/pcm codec
    if (!format.codec().startsWith(QLatin1String("audio/pcm")))
        err = -1;

    if (err >= 0 && format.channelCount() != -1) {
        err = snd_pcm_hw_params_test_channels(pcmHandle, params, format.channelCount());
        if (err >= 0)
            err = snd_pcm_hw_params_set_channels(pcmHandle, params, format.channelCount());
    }

    if (err >= 0 && format.sampleRate() != -1) {
        err = snd_pcm_hw_params_test_rate(pcmHandle, params, format.sampleRate(), 0);
        if (err >= 0)
            err = snd_pcm_hw_params_set_rate(pcmHandle, params, format.sampleRate(), 0);
    }

    if (err >= 0 && pcmFormat != SND_PCM_FORMAT_UNKNOWN)
        err = snd_pcm_hw_params_set_format(pcmHandle, params, pcmFormat);

//.........这里部分代码省略.........

int alsa_init(alsa_dev_t *dev, void *ptr, void (*callback)(snd_async_handler_t *))
{
  snd_pcm_t *phandle;
  snd_pcm_t *chandle;
  
  int err;
  snd_pcm_hw_params_t *hwparams_capture, *hwparams_playback;
  snd_pcm_sw_params_t *swparams_capture, *swparams_playback;
    
  struct sched_param param;
  
  err = sched_getparam(0, &param);
  if (err < 0) {
    perror("sched_getparam():");
    exit(-1);
  }
  
  param.sched_priority = sched_get_priority_max(SCHED_FIFO);
  err = sched_setscheduler(0, SCHED_FIFO, &param);
  if (err < 0) {
    perror("sched_setscheduler():");
   exit(-1);
  }  

  snd_pcm_hw_params_alloca(&hwparams_capture);
  snd_pcm_sw_params_alloca(&swparams_capture);  
  
  snd_pcm_hw_params_alloca(&hwparams_playback);
  snd_pcm_sw_params_alloca(&swparams_playback);   
  
  err = snd_output_stdio_attach(&dev->output, stdout, 0);
  if (err < 0) {
    printf("Output failed: %s\n", snd_strerror(err));
    exit(-1);
  }  
  
  printf("Playback device is %s\n", dev->pdevice);
  printf("Stream parameters are %dHz, %s, %d channels\n", dev->rate, snd_pcm_format_name(dev->format), dev->channels);
  
  if ((err = snd_pcm_open(&phandle, dev->pdevice, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
    printf("Playback open error: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  if ((err = alsa_set_hwparams(dev, phandle, hwparams_playback, SND_PCM_ACCESS_MMAP_INTERLEAVED)) < 0) {
    printf("Setting of hwparams_playback failed: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  if ((err = alsa_set_swparams(dev, phandle, swparams_playback)) < 0) {
    printf("Setting of swparams_playback failed: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  snd_pcm_dump(phandle, dev->output);  
  
  printf("Capture device is %s\n", dev->cdevice);
  
  if ((err = snd_pcm_open(&chandle, dev->cdevice, SND_PCM_STREAM_CAPTURE, 0)) < 0) {
    printf("Capture open error: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  if ((err = alsa_set_hwparams(dev, chandle, hwparams_capture, SND_PCM_ACCESS_MMAP_INTERLEAVED)) < 0) {
    printf("Setting of hwparams_capture failed: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  if ((err = alsa_set_swparams(dev, chandle, swparams_capture)) < 0) {
    printf("Setting of swparams_capture failed: %s\n", snd_strerror(err));
    exit(-1);
  }
  
  snd_pcm_dump(chandle, dev->output);    
  
  if ((err = snd_pcm_link(phandle, chandle)) < 0)
  {
    printf("snd_pcm_link() failed: %s\n", snd_strerror(err));
    exit(-1);    
  }
  
  dev->chandle = chandle;
  dev->phandle = phandle;

  err = alsa_async_direct_loop(dev, ptr, callback);
  if (err < 0)
    printf("Transfer failed: %s\n", snd_strerror(err));  
  
  return 0;  
}