// Write writes given PCM data.
// Returns wrote value is total bytes was written.
func (handle *Handle) Write(buf []byte) (wrote int, err error) {
frames := len(buf) / handle.SampleSize() / handle.Channels
w := C.snd_pcm_writei(handle.cHandle, unsafe.Pointer(&buf[0]), C.snd_pcm_uframes_t(frames))
// Underrun? Retry.
if w == -C.EPIPE {
C.snd_pcm_prepare(handle.cHandle)
w = C.snd_pcm_writei(handle.cHandle, unsafe.Pointer(&buf[0]), C.snd_pcm_uframes_t(frames))
}
if w < 0 {
return 0, fmt.Errorf("Write failed. %s", strError(_Ctype_int(w)))
}
wrote = int(w)
wrote *= handle.FrameSize()
return wrote, nil
}
// Read reads samples into a buffer and returns the amount read.
func (c *CaptureDevice) Read(buffer interface{}) (samples int, err error) {
bufferType := reflect.TypeOf(buffer)
if !(bufferType.Kind() == reflect.Array ||
bufferType.Kind() == reflect.Slice) {
return 0, errors.New("Read requires an array type")
}
sizeError := errors.New("Read requires a matching sample size")
switch bufferType.Elem().Kind() {
case reflect.Int8:
if c.formatSampleSize() != 1 {
return 0, sizeError
}
case reflect.Int16:
if c.formatSampleSize() != 2 {
return 0, sizeError
}
case reflect.Int32, reflect.Float32:
if c.formatSampleSize() != 4 {
return 0, sizeError
}
case reflect.Float64:
if c.formatSampleSize() != 8 {
return 0, sizeError
}
default:
return 0, errors.New("Read does not support this format")
}
val := reflect.ValueOf(buffer)
length := val.Len()
sliceData := val.Slice(0, length)
var frames = C.snd_pcm_uframes_t(length / c.Channels)
bufPtr := unsafe.Pointer(sliceData.Index(0).Addr().Pointer())
ret := C.snd_pcm_readi(c.h, bufPtr, frames)
if ret == -C.EPIPE {
C.snd_pcm_prepare(c.h)
return 0, ErrOverrun
} else if ret < 0 {
return 0, createError("read error", C.int(ret))
}
samples = int(ret) * c.Channels
return
}
// Skip certain number of frames
func (handle *Handle) SkipFrames(frames int) (int, error) {
// Get safe count of frames which can be forwarded.
var framesForwardable C.snd_pcm_sframes_t
framesForwardable = C.snd_pcm_forwardable(handle.cHandle)
if framesForwardable < 0 {
return 0, errors.New(fmt.Sprintf("Retrieving forwardable frames failed. %s", strError(_Ctype_int(framesForwardable))))
}
if int(_Ctype_int(framesForwardable)) < frames {
frames = int(_Ctype_int(framesForwardable))
}
// Move application frame position forward.
var framesForwarded C.snd_pcm_sframes_t
framesForwarded = C.snd_pcm_forward(handle.cHandle, C.snd_pcm_uframes_t(frames))
if framesForwarded < 0 {
return 0, errors.New(fmt.Sprintf("Cannot forward frames. %s", strError(_Ctype_int(framesForwarded))))
}
return int(_Ctype_int(framesForwarded)), nil
}
// ApplyHwParams changes ALSA hardware parameters for the current stream.
func (handle *Handle) ApplyHwParams() error {
var cHwParams *C.snd_pcm_hw_params_t
err := C.snd_pcm_hw_params_malloc(&cHwParams)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot allocate hardware parameter structure. %s",
strError(err)))
}
err = C.snd_pcm_hw_params_any(handle.cHandle, cHwParams)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot initialize hardware parameter structure. %s",
strError(err)))
}
err = C.snd_pcm_hw_params_set_access(handle.cHandle, cHwParams, C.SND_PCM_ACCESS_RW_INTERLEAVED)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set access type. %s",
strError(err)))
}
err = C.snd_pcm_hw_params_set_format(handle.cHandle, cHwParams, C.snd_pcm_format_t(handle.SampleFormat))
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set sample format. %s",
strError(err)))
}
var cSampleRate _Ctype_uint = _Ctype_uint(handle.SampleRate)
err = C.snd_pcm_hw_params_set_rate_near(handle.cHandle, cHwParams, &cSampleRate, nil)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set sample rate. %s",
strError(err)))
}
err = C.snd_pcm_hw_params_set_channels(handle.cHandle, cHwParams, _Ctype_uint(handle.Channels))
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set number of channels. %s",
strError(err)))
}
if handle.Periods > 0 {
// Set number of periods. Periods used to be called fragments.
/*err = C.snd_pcm_hw_params_set_periods(handle.cHandle, cHwParams, _Ctype_uint(handle.Periods), 0)
if err < 0 {
return os.NewError(fmt.Sprintf("Cannot set number of periods. %s",
strError(err)))
}*/
var cPeriods _Ctype_uint = _Ctype_uint(handle.Periods)
var cDir _Ctype_int = 0 // Exact value is <,=,> the returned one following dir (-1,0,1)
err = C.snd_pcm_hw_params_set_periods_near(handle.cHandle, cHwParams, &cPeriods, &cDir)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set number of periods. %s",
strError(err)))
}
}
if handle.Buffersize > 0 {
// Set buffer size (in frames). The resulting latency is given by
// latency = periodsize * periods / (rate * bytes_per_frame)
/*err = C.snd_pcm_hw_params_set_buffer_size(handle.cHandle, cHwParams, _Ctypedef_snd_pcm_uframes_t(handle.Buffersize))
if err < 0 {
return os.NewError(fmt.Sprintf("Cannot set buffersize. %s",
strError(err)))
}*/
var cBuffersize C.snd_pcm_uframes_t = C.snd_pcm_uframes_t(handle.Buffersize)
err = C.snd_pcm_hw_params_set_buffer_size_near(handle.cHandle, cHwParams, &cBuffersize)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set buffersize. %s",
strError(err)))
}
}
// Drain current data and make sure we aren't underrun.
C.snd_pcm_drain(handle.cHandle)
err = C.snd_pcm_hw_params(handle.cHandle, cHwParams)
if err < 0 {
return errors.New(fmt.Sprintf("Cannot set hardware parameters. %s",
strError(err)))
}
C.snd_pcm_hw_params_free(cHwParams)
return nil
}
func (d *device) createDevice(deviceName string, channels int, format Format, rate int, playback bool, bufferParams BufferParams) (err error) {
deviceCString := C.CString(deviceName)
defer C.free(unsafe.Pointer(deviceCString))
var ret C.int
if playback {
ret = C.snd_pcm_open(&d.h, deviceCString, C.SND_PCM_STREAM_PLAYBACK, 0)
} else {
ret = C.snd_pcm_open(&d.h, deviceCString, C.SND_PCM_STREAM_CAPTURE, 0)
}
if ret < 0 {
return fmt.Errorf("could not open ALSA device %s", deviceName)
}
runtime.SetFinalizer(d, (*device).Close)
var hwParams *C.snd_pcm_hw_params_t
ret = C.snd_pcm_hw_params_malloc(&hwParams)
if ret < 0 {
return createError("could not alloc hw params", ret)
}
defer C.snd_pcm_hw_params_free(hwParams)
ret = C.snd_pcm_hw_params_any(d.h, hwParams)
if ret < 0 {
return createError("could not set default hw params", ret)
}
ret = C.snd_pcm_hw_params_set_access(d.h, hwParams, C.SND_PCM_ACCESS_RW_INTERLEAVED)
if ret < 0 {
return createError("could not set access params", ret)
}
ret = C.snd_pcm_hw_params_set_format(d.h, hwParams, C.snd_pcm_format_t(format))
if ret < 0 {
return createError("could not set format params", ret)
}
ret = C.snd_pcm_hw_params_set_channels(d.h, hwParams, C.uint(channels))
if ret < 0 {
return createError("could not set channels params", ret)
}
ret = C.snd_pcm_hw_params_set_rate(d.h, hwParams, C.uint(rate), 0)
if ret < 0 {
return createError("could not set rate params", ret)
}
var bufferSize = C.snd_pcm_uframes_t(bufferParams.BufferFrames)
if bufferParams.BufferFrames == 0 {
// Default buffer size: max buffer size
ret = C.snd_pcm_hw_params_get_buffer_size_max(hwParams, &bufferSize)
if ret < 0 {
return createError("could not get buffer size", ret)
}
}
ret = C.snd_pcm_hw_params_set_buffer_size_near(d.h, hwParams, &bufferSize)
if ret < 0 {
return createError("could not set buffer size", ret)
}
// Default period size: 1/8 of a second
var periodFrames = C.snd_pcm_uframes_t(rate / 8)
if bufferParams.PeriodFrames > 0 {
periodFrames = C.snd_pcm_uframes_t(bufferParams.PeriodFrames)
} else if bufferParams.Periods > 0 {
periodFrames = C.snd_pcm_uframes_t(int(bufferSize) / bufferParams.Periods)
}
ret = C.snd_pcm_hw_params_set_period_size_near(d.h, hwParams, &periodFrames, nil)
if ret < 0 {
return createError("could not set period size", ret)
}
var periods = C.uint(0)
ret = C.snd_pcm_hw_params_get_periods(hwParams, &periods, nil)
if ret < 0 {
return createError("could not get periods", ret)
}
ret = C.snd_pcm_hw_params(d.h, hwParams)
if ret < 0 {
return createError("could not set hw params", ret)
}
d.frames = int(periodFrames)
d.Channels = channels
d.Format = format
d.Rate = rate
d.BufferParams.BufferFrames = int(bufferSize)
d.BufferParams.PeriodFrames = int(periodFrames)
d.BufferParams.Periods = int(periods)
return
}