C++ snd_pcm_hw_params函数代码示例

    void PCMThread::init()
    {
        snd_pcm_t* pcm_handle;
        snd_pcm_hw_params_t* hwparams;
        snd_pcm_uframes_t buffersize_return;
        unsigned int tmp;
        int err;

        std::unique_ptr<PCMHandle> spPCMHandle {new PCMHandle {spSettings_->pcmName_, SND_PCM_STREAM_CAPTURE}};
        QObject::connect (spPCMHandle.get(), &PCMThread::PCMHandle::sigDebug, this, &PCMThread::slotDebug);

        snd_pcm_hw_params_alloca (&hwparams);

        if ( (err = snd_pcm_hw_params_any (*spPCMHandle, hwparams)) < 0)
            throw std::runtime_error (snd_strerror (err));

        if ( (err = snd_pcm_hw_params_set_access (*spPCMHandle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
            throw std::runtime_error (snd_strerror (err));

        if ( (err = snd_pcm_hw_params_set_format (*spPCMHandle, hwparams, SND_PCM_FORMAT_FLOAT)) < 0)
            throw std::runtime_error (snd_strerror (err));

        tmp = spSettings_->rate_;

        if ( (err = snd_pcm_hw_params_set_rate_near (*spPCMHandle, hwparams, &tmp, 0)) < 0)
            throw std::runtime_error (snd_strerror (err));

        tmp = spSettings_->channels_;

        if ( (err = snd_pcm_hw_params_set_channels (*spPCMHandle, hwparams, tmp)) < 0)
            throw std::runtime_error (snd_strerror (err));

        tmp = spSettings_->periods_;

        if ( (err = snd_pcm_hw_params_set_periods (*spPCMHandle, hwparams, tmp, 0)) < 0)
            throw std::runtime_error (snd_strerror (err));

        buffersize_return = spSettings_->periodSize_ * spSettings_->periods_;

        if ( (err = snd_pcm_hw_params_set_buffer_size_near (*spPCMHandle, hwparams, &buffersize_return)) < 0)
            throw std::runtime_error (snd_strerror (err));

        if (buffersize_return != static_cast<snd_pcm_uframes_t> (spSettings_->periodSize_ * spSettings_->periods_))
        {
            DebugHelper dbgHelper;
            dbgHelper << "Period size " << spSettings_->periodSize_ << " not available, using " << 
                            buffersize_return / spSettings_->periods_;
            emit sigDebug (dbgHelper.string());
            periodSize_ = buffersize_return / spSettings_->periods_;
        }
        else
        {
            periodSize_ = spSettings_->periodSize_;
        }

        if ( (err = snd_pcm_hw_params (*spPCMHandle, hwparams)) < 0)
            throw std::runtime_error (snd_strerror (err));

        spPCMHandle_ = std::move (spPCMHandle);
        emit sigDebug ("Initialized : " + QString::fromStdString (spSettings_->pcmName_));
    }

bool QAudioDeviceInfoInternal::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 = 0;
    snd_pcm_t* handle;
    snd_pcm_hw_params_t *params;
    QString dev = device;

    QList<QByteArray> devices = QAudioDeviceInfoInternal::availableDevices(QAudio::AudioOutput);

    if(dev.compare(QLatin1String("default")) == 0) {
#if(SND_LIB_MAJOR == 1 && SND_LIB_MINOR == 0 && SND_LIB_SUBMINOR >= 14)
        dev = QLatin1String(devices.first().constData());
#else
        dev = QLatin1String("hw:0,0");
#endif
    } else {
#if(SND_LIB_MAJOR == 1 && SND_LIB_MINOR == 0 && SND_LIB_SUBMINOR >= 14)
        dev = device;
#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
    }
    if(mode == QAudio::AudioOutput) {
        err=snd_pcm_open( &handle,dev.toLocal8Bit().constData(),SND_PCM_STREAM_PLAYBACK,0);
    } else {
        err=snd_pcm_open( &handle,dev.toLocal8Bit().constData(),SND_PCM_STREAM_CAPTURE,0);
    }
    if(err < 0) {
        handle = 0;
        return false;
    }

    bool testChannel = false;
    bool testCodec = false;
    bool testFreq = false;
    bool testType = false;
    bool testSize = false;

    int  dir = 0;

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

    // set the values!
    snd_pcm_hw_params_set_channels(handle,params,format.channels());
    snd_pcm_hw_params_set_rate(handle,params,format.frequency(),dir);

    err = -1;

    switch(format.sampleSize()) {
        case 8:
            if(format.sampleType() == QAudioFormat::SignedInt)
                err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_S8);
            else if(format.sampleType() == QAudioFormat::UnSignedInt)
                err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_U8);
            break;
        case 16:
            if(format.sampleType() == QAudioFormat::SignedInt) {
                if(format.byteOrder() == QAudioFormat::LittleEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_S16_LE);
                else if(format.byteOrder() == QAudioFormat::BigEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_S16_BE);
            } else if(format.sampleType() == QAudioFormat::UnSignedInt) {
                if(format.byteOrder() == QAudioFormat::LittleEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_U16_LE);
                else if(format.byteOrder() == QAudioFormat::BigEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_U16_BE);
            }
            break;
        case 32:
            if(format.sampleType() == QAudioFormat::SignedInt) {
                if(format.byteOrder() == QAudioFormat::LittleEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_S32_LE);
                else if(format.byteOrder() == QAudioFormat::BigEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_S32_BE);
            } else if(format.sampleType() == QAudioFormat::UnSignedInt) {
                if(format.byteOrder() == QAudioFormat::LittleEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_U32_LE);
                else if(format.byteOrder() == QAudioFormat::BigEndian)
                    err = snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORMAT_U32_BE);
            }
    }

    // For now, just accept only audio/pcm codec
    if(!format.codec().startsWith(QLatin1String("audio/pcm"))) {
        err=-1;
    } else
//.........这里部分代码省略.........

/* setup alsa data format and buffer geometry */
static inline int alsa_set_hwparams(ao_device *device,
                                    ao_sample_format *format)
{
	ao_alsa_internal *internal  = (ao_alsa_internal *) device->internal;
	snd_pcm_hw_params_t   *params;
	int err;
	unsigned int rate = internal->sample_rate = format->rate;

	/* allocate the hardware parameter structure */
	snd_pcm_hw_params_alloca(&params);

	/* fetch all possible hardware parameters */
	err = snd_pcm_hw_params_any(internal->pcm_handle, params);
	if (err < 0){
          adebug("snd_pcm_hw_params_any() failed.\n"
                 "        Device exists but no matching hardware?\n");
          return err;
        }

	/* set the access type */
	err = snd_pcm_hw_params_set_access(internal->pcm_handle,
			params, internal->access_mask);
	if (err < 0){
          adebug("snd_pcm_hw_params_set_access() failed.\n");
          return err;
        }

	/* set the sample bitformat */
	err = snd_pcm_hw_params_set_format(internal->pcm_handle,
			params, internal->bitformat);
	if (err < 0){

          /* the device may support a greater bit-depth than the one
             requested. */
          switch(internal->bitformat){
          case SND_PCM_FORMAT_U8:
            if (!snd_pcm_hw_params_set_format(internal->pcm_handle,
                                              params, SND_PCM_FORMAT_S16)){
              adebug("snd_pcm_hw_params_set_format() unable to open %d bit playback.\n",format->bits);
              adebug("snd_pcm_hw_params_set_format() using 16 bit playback instead.\n");
              format->bits = 16;
              break;
            }
          case SND_PCM_FORMAT_S16:
            if (!snd_pcm_hw_params_set_format(internal->pcm_handle,
                                              params, SND_PCM_FORMAT_S24)){
              adebug("snd_pcm_hw_params_set_format() unable to open %d bit playback.\n",format->bits);
              adebug("snd_pcm_hw_params_set_format() using 24 bit playback instead.\n");
              format->bits = 24;
              break;
            }
          case SND_PCM_FORMAT_S24:
            if (!snd_pcm_hw_params_set_format(internal->pcm_handle,
                                              params, SND_PCM_FORMAT_S32)){
              adebug("snd_pcm_hw_params_set_format() unable to open %d bit playback.\n",format->bits);
              adebug("snd_pcm_hw_params_set_format() using 32 bit playback instead.\n");
              format->bits = 32;
              break;
            }
          case SND_PCM_FORMAT_S32:
            adebug("snd_pcm_hw_params_set_format() failed.\n");
            return err;
          }
        }

	/* set the number of channels */
	err = snd_pcm_hw_params_set_channels(internal->pcm_handle,
			params, (unsigned int)device->output_channels);
	if (err < 0){
          adebug("snd_pcm_hw_params_set_channels() failed.\n");
          return err;
        }

	/* set the sample rate */
	err = snd_pcm_hw_params_set_rate_near(internal->pcm_handle,
			params, &rate, 0);
	if (err < 0){
          adebug("snd_pcm_hw_params_set_rate_near() failed.\n");
          return err;
        }
	if (rate > 1.05 * format->rate || rate < 0.95 * format->rate) {
          awarn("sample rate %i not supported "
                "by the hardware, using %u\n", format->rate, rate);
	}

	/* set the time per hardware sample transfer */
        if(internal->period_time==0)
          internal->period_time=internal->buffer_time/4;

	err = snd_pcm_hw_params_set_period_time_near(internal->pcm_handle,
			params, &(internal->period_time), 0);
	if (err < 0){
          adebug("snd_pcm_hw_params_set_period_time_near() failed.\n");
          return err;
        }

	/* set the length of the hardware sample buffer in microseconds */
        /* some plug devices have very high minimum periods; don't
           allow a buffer size small enough that it's ~ guaranteed to
//.........这里部分代码省略.........

//
// Set up both the audio and video capturing on the card
//
void an_configure_capture_card( void )
{
    struct v4l2_cropcap cropcap;
    struct v4l2_crop    crop;
    struct v4l2_format  fmt;
    sys_config info;
    int input;
    u32 pix_fmt;

    dvb_config_get( &info );

    CLEAR(cropcap);
    CLEAR(crop);
    CLEAR(fmt);

    m_width  = PAL_WIDTH_CAPTURE;
    m_height = PAL_HEIGHT_CAPTURE;

    // Set the cropping, ignore any errors
    cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    if (ioctl(m_i_fd, VIDIOC_CROPCAP, &cropcap)==0) {
            crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            crop.c    = cropcap.defrect; /* reset to default */

            ioctl(m_i_fd, VIDIOC_S_CROP, &crop);
    }
    //
    // Analogue Video capture
    //
    pix_fmt = V4L2_PIX_FMT_YUV420;
    m_sws   = NULL;

    fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width       = m_width;
    fmt.fmt.pix.height      = m_height;
    fmt.fmt.pix.pixelformat = pix_fmt;
    fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;

    if (ioctl(m_i_fd, VIDIOC_S_FMT, &fmt) == 0)
    {
        an_set_image_size( AV_PIX_FMT_YUV420P );
    }
    else
    {
        pix_fmt = V4L2_PIX_FMT_YUYV; // capture format
        fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        fmt.fmt.pix.width       = m_width;
        fmt.fmt.pix.height      = m_height;
        fmt.fmt.pix.pixelformat = pix_fmt;
        fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
        if (ioctl(m_i_fd, VIDIOC_S_FMT, &fmt) == 0)
        {
            // Format conversion will be required
            m_sws = sws_getContext( m_width, m_height, AV_PIX_FMT_YUYV422,
                                    m_width, m_height, AV_PIX_FMT_YUV420P,
                                    SWS_BICUBIC, NULL,NULL, NULL);
            an_set_image_size( AV_PIX_FMT_YUYV422 );
        }
        else
        {
            logger("CAP ANALOGUE FORMAT NOT SUPPORTED");
        }
    }

    if(ioctl(m_i_fd, VIDIOC_G_FMT, &fmt)<0 )
        logger("can't get format");

    //	input = V4L2_INPUT_TYPE_CAMERA;
    input = info.video_capture_device_input;

    if( ioctl( m_i_fd, VIDIOC_S_INPUT, &input) < 0 )
    {
        loggerf("CAP Error VIDIOC_S_INPUT %d",input);
    }

/*
    v4l2_streamparm parm;
    memset(&parm,0,sizeof(v4l2_streamparm));
    parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    parm.parm.capture.capturemode = 0;
    parm.parm.capture.readbuffers = 0;

    if( ioctl( m_i_fd, VIDIOC_S_PARM, &parm) < 0 )
    {
        loggerf("CAP Error VIDIOC_S_PARM");
    }
*/
    info.video_bitrate = calculate_video_bitrate();

    //
    // Analogue sound capture
    //
    snd_pcm_hw_params_t *hw_params;

    if(snd_pcm_open(&m_audio_handle, "pulse", SND_PCM_STREAM_CAPTURE, 0)< 0 )
    {
//.........这里部分代码省略.........

static int initalsa(char *filename)
{
	snd_pcm_hw_params_t *hw_params;
	int err;

	if ((err =
	     snd_pcm_open(&capture_handle, filename,
			  SND_PCM_STREAM_CAPTURE, 0)) < 0) {
		fprintf(stderr, "cannot open audio device %s (%s)\n",
			filename, snd_strerror(err));
		return 0;
	}

	if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
		fprintf(stderr,
			"cannot allocate hardware parameter structure (%s)\n",
			snd_strerror(err));
		return 0;
	}

	if ((err = snd_pcm_hw_params_any(capture_handle, hw_params)) < 0) {
		fprintf(stderr,
			"cannot initialize hardware parameter structure (%s)\n",
			snd_strerror(err));
		return 0;
	}

	if ((err =
	     snd_pcm_hw_params_set_access(capture_handle, hw_params,
					  SND_PCM_ACCESS_RW_INTERLEAVED)) <
	    0) {
		fprintf(stderr, "cannot set access type (%s)\n",
			snd_strerror(err));
		return 0;
	}

	if ((err =
	     snd_pcm_hw_params_set_format(capture_handle, hw_params,
					  SND_PCM_FORMAT_S16)) < 0) {
		fprintf(stderr, "cannot set sample format (%s)\n",
			snd_strerror(err));
		return 0;
	}

	if ((err =
	     snd_pcm_hw_params_set_rate(capture_handle, hw_params, 48000,
					0)) < 0) {
		fprintf(stderr, "cannot set sample rate (%s)\n",
			snd_strerror(err));
		return 0;
	}

	for(nbch=2;nbch>0;nbch--)  {
		if (snd_pcm_hw_params_set_channels(capture_handle, hw_params, nbch)==0)	
			break;
	}

	if (nbch ==0) {
		fprintf(stderr, "cannot set number of channels\n");
		return 0;
	}

        if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
                fprintf(stderr, "cannot set parameters (%s)\n",
                        snd_strerror(err));
		return 0;
	}
        snd_pcm_hw_params_free(hw_params);

	if ((err = snd_pcm_prepare(capture_handle)) < 0) {
		fprintf(stderr,
			"cannot prepare audio interface for use (%s)\n",
			snd_strerror(err));
		return 0;
	}
	return nbch;
}

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;
}

static int
set_hwparams (GstAlsaSrc * alsa)
{
  guint rrate;
  gint err;
  snd_pcm_hw_params_t *params;

  snd_pcm_hw_params_malloc (&params);

  /* choose all parameters */
  CHECK (snd_pcm_hw_params_any (alsa->handle, params), no_config);
  /* set the interleaved read/write format */
  CHECK (snd_pcm_hw_params_set_access (alsa->handle, params, alsa->access),
      wrong_access);
  /* set the sample format */
  CHECK (snd_pcm_hw_params_set_format (alsa->handle, params, alsa->format),
      no_sample_format);
  /* set the count of channels */
  CHECK (snd_pcm_hw_params_set_channels (alsa->handle, params, alsa->channels),
      no_channels);
  /* set the stream rate */
  rrate = alsa->rate;
  CHECK (snd_pcm_hw_params_set_rate_near (alsa->handle, params, &rrate, NULL),
      no_rate);
  if (rrate != alsa->rate)
    goto rate_match;

#ifndef GST_DISABLE_GST_DEBUG
  /* get and dump some limits */
  {
    guint min, max;

    snd_pcm_hw_params_get_buffer_time_min (params, &min, NULL);
    snd_pcm_hw_params_get_buffer_time_max (params, &max, NULL);

    GST_DEBUG_OBJECT (alsa, "buffer time %u, min %u, max %u",
        alsa->buffer_time, min, max);

    snd_pcm_hw_params_get_period_time_min (params, &min, NULL);
    snd_pcm_hw_params_get_period_time_max (params, &max, NULL);

    GST_DEBUG_OBJECT (alsa, "period time %u, min %u, max %u",
        alsa->period_time, min, max);

    snd_pcm_hw_params_get_periods_min (params, &min, NULL);
    snd_pcm_hw_params_get_periods_max (params, &max, NULL);

    GST_DEBUG_OBJECT (alsa, "periods min %u, max %u", min, max);
  }
#endif

  if (alsa->buffer_time != -1) {
    /* set the buffer time */
    CHECK (snd_pcm_hw_params_set_buffer_time_near (alsa->handle, params,
            &alsa->buffer_time, NULL), buffer_time);
    GST_DEBUG_OBJECT (alsa, "buffer time %u", alsa->buffer_time);
  }
  if (alsa->period_time != -1) {
    /* set the period time */
    CHECK (snd_pcm_hw_params_set_period_time_near (alsa->handle, params,
            &alsa->period_time, NULL), period_time);
    GST_DEBUG_OBJECT (alsa, "period time %u", alsa->period_time);
  }

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

  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);

  snd_pcm_hw_params_free (params);
  return 0;

  /* ERRORS */
no_config:
  {
    GST_ELEMENT_ERROR (alsa, RESOURCE, SETTINGS, (NULL),
        ("Broken configuration for recording: 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 recording: %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 recording: %s", snd_strerror (err)));
    snd_pcm_hw_params_free (params);
    return err;
  }
no_channels:
//.........这里部分代码省略.........

int main() {
  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;

  /* 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 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, 2);

  /* 44100 bits/second sampling rate (CD quality) */
  val = 44100;
  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 5 seconds */
  snd_pcm_hw_params_get_period_time(params,
                                    &val, &dir);
  /* 5 seconds in microseconds divided by
   * period time */
  loops = 5000000 / val;

  while (loops > 0) {
    loops--;
    rc = read(0, 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) {
      fprintf(stderr,
              "error from writei: %s\n",
              snd_strerror(rc));
    }  else if (rc != (int)frames) {
      fprintf(stderr,
              "short write, write %d frames\n", rc);
    }
  }

  snd_pcm_drain(handle);
  snd_pcm_close(handle);
  free(buffer);
//.........这里部分代码省略.........

bool CAESinkALSA::InitializeHW(const ALSAConfig &inconfig, ALSAConfig &outconfig)
{
  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   = inconfig.sampleRate;
  unsigned int channelCount = inconfig.channels;
#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

  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 (inconfig.channels > channelCount)
  {
    CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Unable to open the required number of channels");
  }

  /* update outconfig */
  outconfig.channels = channelCount;

  snd_pcm_format_t fmt = AEFormatToALSAFormat(inconfig.format);
  outconfig.format = inconfig.format;

  if (fmt == SND_PCM_FORMAT_UNKNOWN)
  {
    /* if we dont support the requested format, fallback to float */
    fmt = SND_PCM_FORMAT_FLOAT;
    outconfig.format = AE_FMT_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(outconfig.format));
    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 */
      outconfig.format = i;
      CLog::Log(LOGINFO, "CAESinkALSA::InitializeHW - Using data format %s", CAEUtil::DataFormatToStr(outconfig.format));
      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.........

static boolean tsmf_alsa_set_format(ITSMFAudioDevice* audio,
	uint32 sample_rate, uint32 channels, uint32 bits_per_sample)
{
	int error;
	snd_pcm_uframes_t frames;
	snd_pcm_hw_params_t* hw_params;
	snd_pcm_sw_params_t* sw_params;
	TSMFALSAAudioDevice* alsa = (TSMFALSAAudioDevice*) audio;

	if (!alsa->out_handle)
		return false;

	snd_pcm_drop(alsa->out_handle);

	alsa->actual_rate = alsa->source_rate = sample_rate;
	alsa->actual_channels = alsa->source_channels = channels;
	alsa->bytes_per_sample = bits_per_sample / 8;

	error = snd_pcm_hw_params_malloc(&hw_params);
	if (error < 0)
	{
		DEBUG_WARN("snd_pcm_hw_params_malloc failed");
		return false;
	}
	snd_pcm_hw_params_any(alsa->out_handle, hw_params);
	snd_pcm_hw_params_set_access(alsa->out_handle, hw_params,
		SND_PCM_ACCESS_RW_INTERLEAVED);
	snd_pcm_hw_params_set_format(alsa->out_handle, hw_params,
		SND_PCM_FORMAT_S16_LE);
	snd_pcm_hw_params_set_rate_near(alsa->out_handle, hw_params,
		&alsa->actual_rate, NULL);
	snd_pcm_hw_params_set_channels_near(alsa->out_handle, hw_params,
		&alsa->actual_channels);
	frames = sample_rate;
	snd_pcm_hw_params_set_buffer_size_near(alsa->out_handle, hw_params,
		&frames);
	snd_pcm_hw_params(alsa->out_handle, hw_params);
	snd_pcm_hw_params_free(hw_params);

	error = snd_pcm_sw_params_malloc(&sw_params);
	if (error < 0)
	{
		DEBUG_WARN("snd_pcm_sw_params_malloc");
		return false;
	}
	snd_pcm_sw_params_current(alsa->out_handle, sw_params);
	snd_pcm_sw_params_set_start_threshold(alsa->out_handle, sw_params,
		frames / 2);
	snd_pcm_sw_params(alsa->out_handle, sw_params);
	snd_pcm_sw_params_free(sw_params);

	snd_pcm_prepare(alsa->out_handle);

	DEBUG_DVC("sample_rate %d channels %d bits_per_sample %d",
		sample_rate, channels, bits_per_sample);
	DEBUG_DVC("hardware buffer %d frames", (int)frames);
	if ((alsa->actual_rate != alsa->source_rate) ||
		(alsa->actual_channels != alsa->source_channels))
	{
		DEBUG_DVC("actual rate %d / channel %d is different "
			"from source rate %d / channel %d, resampling required.",
			alsa->actual_rate, alsa->actual_channels,
			alsa->source_rate, alsa->source_channels);
	}
	return true;
}

int setparams_set(snd_pcm_t *handle,
		  snd_pcm_hw_params_t *params,
		  snd_pcm_sw_params_t *swparams,
		  const char *id)
{
	int err;
	snd_pcm_uframes_t val;
	unsigned int sleep_min = 0;

	err = snd_pcm_hw_params(handle, params);
	if (err < 0) {
		printf("Unable to set hw params for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	err = snd_pcm_sw_params_current(handle, swparams);
	if (err < 0) {
		printf("Unable to determine current swparams for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	err = snd_pcm_sw_params_set_start_threshold(handle, swparams, 0x7fffffff);
	if (err < 0) {
		printf("Unable to set start threshold mode for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	tick_time_ok = 0;
	if (tick_time > 0) {
		int time, ttime;
		snd_pcm_hw_params_get_period_time(params, &time, NULL);
		 snd_pcm_hw_params_get_tick_time(params, &ttime, NULL);
		if (time < ttime) {
			printf("Skipping to set minimal sleep: period time < tick time\n");
		} else if (ttime <= 0) {
			printf("Skipping to set minimal sleep: tick time <= 0 (%i)\n", ttime);
		} else {
			sleep_min = tick_time / ttime;
			if (sleep_min <= 0)
				sleep_min = 1;
			err = snd_pcm_sw_params_set_sleep_min(handle, swparams, sleep_min);
			if (err < 0) {
				printf("Unable to set minimal sleep %i for %s: %s\n", sleep_min, id, snd_strerror(err));
				return err;
			}
			tick_time_ok = sleep_min * ttime;
		}
	}
	if (!block)
		val = 4;
	else
		snd_pcm_hw_params_get_period_size(params, &val, NULL);
	if (tick_time_ok > 0)
		val = 16;
	err = snd_pcm_sw_params_set_avail_min(handle, swparams, val);
	if (err < 0) {
		printf("Unable to set avail min for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	val = !block ? 4 : 1;
	err = snd_pcm_sw_params_set_xfer_align(handle, swparams, val);
	if (err < 0) {
		printf("Unable to set transfer align for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	err = snd_pcm_sw_params(handle, swparams);
	if (err < 0) {
		printf("Unable to set sw params for %s: %s\n", id, snd_strerror(err));
		return err;
	}
	return 0;
}

int main() {
  long loops;
  int rc, rc2;
  int size;
  snd_pcm_t *handle;
  snd_pcm_t *handle2;
  snd_pcm_hw_params_t *params;
  snd_pcm_hw_params_t *params2;
  unsigned int val, val2;
  int dir, dir2;
  snd_pcm_uframes_t frames, frames2;
  char *buffer;


  /* Open PCM device for recording (capture). */
  rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_CAPTURE | SND_PCM_NONBLOCK, 0);
//  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);
  }


  /* Open PCM device for playback. */
  rc2 = snd_pcm_open(&handle2, "default", SND_PCM_STREAM_PLAYBACK, 0);
  if (rc2 < 0) {
    fprintf(stderr, "unable to open pcm device: %s\n", snd_strerror(rc2));
    exit(1);
  }


/* Allocate a hardware parameters object. */
  snd_pcm_hw_params_alloca(&params2);

  /* Fill it in with default values. */
  snd_pcm_hw_params_any(handle2, params2);

  /* Set the desired hardware parameters. */

  /* Interleaved mode */
  snd_pcm_hw_params_set_access(handle2, params2, SND_PCM_ACCESS_RW_INTERLEAVED);

  /* Signed 16-bit little-endian format */
  snd_pcm_hw_params_set_format(handle2, params2, SND_PCM_FORMAT_S16_LE);

  /* Two channels (stereo) */
  snd_pcm_hw_params_set_channels(handle2, params2, 2);

  /* 44100 bits/second sampling rate (CD quality) */
  val2 = 96000;
  snd_pcm_hw_params_set_rate_near(handle2, params2, &val2, &dir2);

  /* Set period size to 32 frames. */
  frames2 = 8;
  snd_pcm_hw_params_set_period_size_near(handle2, params2, &frames2, &dir2);

  /* Write the parameters to the driver */
  rc2 = snd_pcm_hw_params(handle2, params2);
  if (rc2 < 0) {
    fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(rc2));
    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, 2);

  /* 44100 bits/second sampling rate (CD quality) */
  val = 96000;
  //val = 48000;
  snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);

  /* Set period size to 32 frames. */
  frames = 8;
  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);
//.........这里部分代码省略.........

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;
    }
  }

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

  /* 
   We want to make sure, that we have max 200 ms Buffer with 
   a periodSize of approx 50 ms. Choosing a higher bufferSize
   will cause problems with menu sounds. Buffer will be increased
   after those are fixed.
  */
  periodSize  = std::min(periodSize, (snd_pcm_uframes_t) sampleRate / 20);
  bufferSize  = std::min(bufferSize, (snd_pcm_uframes_t) sampleRate / 5);
  
  /* 
   According to upstream we should set buffer size first - so make sure it is always at least
   4x period size to not get underruns (some systems seem to have issues with only 2 periods)
  */
  periodSize = std::min(periodSize, bufferSize / 4);

  CLog::Log(LOGDEBUG, "CAESinkALSA::InitializeHW - Request: periodSize %lu, bufferSize %lu", periodSize, bufferSize);
//.........这里部分代码省略.........

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.........

static int alsa_open (struct sound_params *sound_params)
{
	snd_pcm_hw_params_t *hw_params;
	int err;
	unsigned int period_time;
	unsigned int buffer_time;
	snd_pcm_uframes_t chunk_frames;
	snd_pcm_uframes_t buffer_frames;
	char fmt_name[128];

	switch (sound_params->fmt & SFMT_MASK_FORMAT) {
		case SFMT_S8:
			params.format = SND_PCM_FORMAT_S8;
			break;
		case SFMT_U8:
			params.format = SND_PCM_FORMAT_U8;
			break;
		case SFMT_S16:
			params.format = SND_PCM_FORMAT_S16;
			break;
		case SFMT_U16:
			params.format = SND_PCM_FORMAT_U16;
			break;
		case SFMT_S32:
			params.format = SND_PCM_FORMAT_S32;
			break;
		case SFMT_U32:
			params.format = SND_PCM_FORMAT_U32;
			break;
		default:
			error ("Unknown sample format: %s",
					sfmt_str(sound_params->fmt, fmt_name, sizeof(fmt_name)));
			params.format = SND_PCM_FORMAT_UNKNOWN;
			return 0;
	}

	if ((err = snd_pcm_open(&handle, options_get_str("AlsaDevice"),
					SND_PCM_STREAM_PLAYBACK,
					SND_PCM_NONBLOCK)) < 0) {
		error ("Can't open audio: %s", snd_strerror(err));
		return 0;
	}

	if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
		error ("Can't allocate alsa hardware parameters structure: %s",
				snd_strerror(err));
		return 0;
	}

	if ((err = snd_pcm_hw_params_any (handle, hw_params)) < 0) {
		error ("Can't initialize hardware parameters structure: %s",
				snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	if ((err = snd_pcm_hw_params_set_access (handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
		error ("Can't set alsa access type: %s", snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	if ((err = snd_pcm_hw_params_set_format (handle, hw_params,
					params.format)) < 0) {
		error ("Can't set sample format: %s", snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	params.rate = sound_params->rate;
	if ((err = snd_pcm_hw_params_set_rate_near (handle, hw_params,
					&params.rate, 0)) < 0) {
		error ("Can't set sample rate: %s", snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	logit ("Set rate to %u", params.rate);

	if ((err = snd_pcm_hw_params_set_channels (handle, hw_params,
					sound_params->channels)) < 0) {
		error ("Can't set number of channels: %s", snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	if ((err = snd_pcm_hw_params_get_buffer_time_max(hw_params,
					&buffer_time, 0)) < 0) {
		error ("Can't get maximum buffer time: %s", snd_strerror(err));
		snd_pcm_hw_params_free (hw_params);
		return 0;
	}

	if (buffer_time > BUFFER_MAX_USEC)
		buffer_time = BUFFER_MAX_USEC;
	period_time = buffer_time / 4;

	if ((err = snd_pcm_hw_params_set_period_time_near(handle, hw_params,
					&period_time, 0)) < 0) {
		error ("Can't set period time: %s", snd_strerror(err));
//.........这里部分代码省略.........