func (m *Mixer) Close() error {
if err := alsa(C.snd_mixer_close(m.mixer)); err != nil {
return fmt.Errorf("alsa: closing mixer: %v", err)
}
return nil
}
func OpenMixer() (*Mixer, error) {
var mix *C.snd_mixer_t
if err := alsa(C.snd_mixer_open(&mix, 0)); err != nil {
return nil, fmt.Errorf("alsa: opening mixer: %v", err)
}
defer func() {
if mix != nil {
if err := alsa(C.snd_mixer_close(mix)); err != nil {
log.Printf("alsa: closing mixer: %v", err)
}
}
}()
card := C.CString(alsaCard)
defer C.free(unsafe.Pointer(card))
if err := alsa(C.snd_mixer_attach(mix, card)); err != nil {
return nil, fmt.Errorf("alsa: attaching mixer master volume: %v", err)
}
if err := alsa(C.snd_mixer_selem_register(mix, nil, nil)); err != nil {
return nil, fmt.Errorf("alsa: mixer register: %v", err)
}
if err := alsa(C.snd_mixer_load(mix)); err != nil {
return nil, fmt.Errorf("alsa: mixer load: %v", err)
}
var sid *C.snd_mixer_selem_id_t
if err := alsa(C.snd_mixer_selem_id_malloc(&sid)); err != nil {
return nil, fmt.Errorf("alsa: allocating mixer element: %v", err)
}
name := C.CString(mixerElemMaster)
defer C.free(unsafe.Pointer(name))
C.snd_mixer_selem_id_set_name(sid, name)
elem := C.snd_mixer_find_selem(mix, sid)
if elem == nil {
return nil, fmt.Errorf("alsa: cannot find mixer element")
}
if C.snd_mixer_selem_has_playback_volume(elem) == 0 {
return nil, errors.New("alsa: mixer has no playback volume")
}
var min, max C.long
if err := alsa(C.snd_mixer_selem_get_playback_volume_range(elem, &min, &max)); err != nil {
return nil, fmt.Errorf("alsa: cannot get volume range: %v", err)
}
if C.snd_mixer_selem_has_playback_switch(elem) == 0 {
return nil, errors.New("alsa: mixer has no mute")
}
m := &Mixer{
mixer: mix,
elem: elem,
min: int32(min),
max: int32(max),
}
mix = nil
elem = nil
return m, nil
}