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[Raymond <1497666@xxxxxxxxxxxxxxxxxx>]

http://cgit.freedesktop.org/pulseaudio/pulseaudio/tree/src/modules/alsa
/alsa-mixer.c


seem pulseaudio only control left channel when it only use the virtual master playback volume control


in function element_set_volume, it check the element has left and right channel 


static int element_set_volume(pa_alsa_element *e, snd_mixer_t *m, const pa_channel_map *cm, pa_cvolume *v, bool deferred_volume, bool write_to_hw) {

    snd_mixer_selem_id_t *sid;
    pa_cvolume rv;
    snd_mixer_elem_t *me;
    snd_mixer_selem_channel_id_t c;
    pa_channel_position_mask_t mask = 0;
    unsigned k;

    pa_assert(m);
    pa_assert(e);
    pa_assert(cm);
    pa_assert(v);
    pa_assert(pa_cvolume_compatible_with_channel_map(v, cm));

    SELEM_INIT(sid, e->alsa_name);
    if (!(me = snd_mixer_find_selem(m, sid))) {
        pa_log_warn("Element %s seems to have disappeared.", e->alsa_name);
        return -1;
    }

    pa_cvolume_mute(&rv, cm->channels);

    for (c = 0; c <= SND_MIXER_SCHN_LAST; c++) {
        int r;
        pa_volume_t f = PA_VOLUME_MUTED;
        bool found = false;

        for (k = 0; k < cm->channels; k++)
            if (e->masks[c][e->n_channels-1] & PA_CHANNEL_POSITION_MASK(cm->map[k])) {
                found = true;
                if (v->values[k] > f)
                    f = v->values[k];
            }

        if (!found) {
            /* Hmm, so this channel does not exist in the volume
             * struct, so let's bind it to the overall max of the
             * volume. */
            f = pa_cvolume_max(v);
        }

        if (e->has_dB) {
            long value = to_alsa_dB(f);
            int rounding;

            if (e->volume_limit >= 0 && value > (e->max_dB * 100))
                value = e->max_dB * 100;

            if (e->direction == PA_ALSA_DIRECTION_OUTPUT) {
                /* If we call set_playback_volume() without checking first
                 * if the channel is available, ALSA behaves very
                 * strangely and doesn't fail the call */
                if (snd_mixer_selem_has_playback_channel(me, c)) {


** Changed in: alsa-driver (Ubuntu)
       Status: New => Incomplete

-- 
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to alsa-driver in Ubuntu.
https://bugs.launchpad.net/bugs/1497666

Title:
  No right channel sound on Creative Xtreme Audio (CA0106)  in  Ubuntu
  14.04-15.10

Status in alsa-driver package in Ubuntu:
  Incomplete

Bug description:
  After a fresh install of Ubuntu 14.04, 15.04, 15.10 and on the liveCD,
  There is no sound on right channel. But it works perfectly in Win
  7/10. It also worked perfectly on Ubuntu 12.04 My sound card is
  Creative Xtreme Audio (PCI CA0106).

  In the forum, many users also have experienced this bug with the
  incorrect default alsamixer settings.

  http://ubuntuforums.org/showthread.php?t=2217724

  Here are my alsa-info.sh results.

  http://www.alsa-
  project.org/db/?f=e3ae99437c3d283b35cac7c33ace996bedf43a16

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