// Open opens a stream.
func (handle *Handle) Open(device string, streamType StreamType, mode int) error {
cDevice := C.CString(device)
defer C.free(unsafe.Pointer(cDevice))
err := C.snd_pcm_open(&(handle.cHandle), cDevice,
_Ctype_snd_pcm_stream_t(streamType),
_Ctype_int(mode))
if err < 0 {
return errors.New(fmt.Sprintf("Cannot open audio device '%s'. %s",
device, strError(err)))
}
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
}