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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1497666/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp