[gst-devel] Using Mixer Interface

[Mathis Hofer]

Hi

I don't know if the mixer interface can be used from the command line.

But as an example here is some C code to adjust the master volume and
balance:

*****
static void adjust_mixer(int volume, int balance)
{
    GstElement *mixer;
    const GList *tracks;

    mixer = gst_element_factory_make("alsamixer", "mixer");
    g_object_set(G_OBJECT(mixer),
                 "device", "hw:0",
                 NULL);
    gst_element_set_state(mixer, GST_STATE_READY);

    for (tracks = gst_mixer_list_tracks(GST_MIXER(mixer));
         tracks; tracks = tracks->next) {
	    GstMixerTrack *track = (GstMixerTrack *)tracks->data;

	    if (GST_MIXER_TRACK_HAS_FLAG(track, GST_MIXER_TRACK_MASTER)) {
            // Set master volume and balance
            double volume = ((double)volume/100.0
                             * (double)(track->max_volume -
track->min_volume)) - track->min_volume;

            int volumes[2];

            // Left channel
            volumes[0] = (int)(volume/50.0 * (50.0-MAX(balance, 0)));
            // Right channel
            volumes[1] = (int)(volume/50.0 * (50.0-abs(MIN(balance, 0))));

            gst_mixer_set_volume(GST_MIXER(mixer), track, volumes);
        } else {

        }
    }

    gst_element_set_state(mixer, GST_STATE_NULL);
    gst_object_unref(GST_OBJECT(mixer));
*****

Hope this helps...

Regards,
Mathis

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