Question

I need to control the audio output device at run time :

1) Main Speaker only
2) Headphone Only
3) Headphone + Main Speaker both together

My application take run time decision to switch among above combinations. What ALSA API should I use for above purpose.

(I use Linux 3.0, ALSA, C, TI tlv320aic3x , ARM).

Answer 1

You may use this:

int snd_mixer_selem_set_playback_volume(snd_mixer_elem_t *elem,
snd_mixer_selem_channel_id_t channel, long value)       

which sets value of playback volume control of a mixer simple element.

here is a source code example:

        /* Set new volume */
         if (snd_mixer_selem_set_playback_volume(elem,
             SND_MIXER_SCHN_FRONT_LEFT, left_volume) != 0)
                 return (-1);
         if (snd_mixer_selem_set_playback_volume(elem,
             SND_MIXER_SCHN_FRONT_RIGHT, right_volume) != 0)
                 return (-1);