Can't unmute by hotkeys if previously muted

[Marco Chiappetta]

Machine: Asus EeePC 1201N (EU: Atom 330@1.6 Ghz, 3GB Ram, Nvidia ION GPU).
Release: Xubuntu 11.10 Oneiric Ocelot (latest upgrade: Thu Oct 27 22:46:45 UTC 2011).
Pkg_version: xfce4-mixer 1:4.8.0-2ubuntu1.

1) Try to mute the mixer by pressing "Fn+Mute" hotkeys -> The Master channel mutes (any other channel remains at its previous state).
2) Press "Fn+Mute" again to unmute the Master channel -> on both xfce4-mixer and alsa-mixer the Master channel appears to be unmuted and an "unmuted audio" notification shows up but I can't hear any sound.

EXPECTED: A good working hotkeys combination to mute/unmute audio.

WORKAROUND: After having muted with "Fn+Mute" (its Fn+F10 on my keyboard) you can still re-enable sound by pressing "Fn+Vol-" and then "Fn+Vol+". This doesn't work when using headphones (??).

MINOR_INFO: pavucontrol returns a "** (pavucontrol:3706): DEBUG: Failed to initialize device manager extension: No such extension" after executing it from a terminal.

Thank you in advance!

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Rich Lawrence (arr-dee-ell+launchpad)]

On my system, a XF86AudioMute buttonpress seems to be muting the pulseaudio server - it can be unmuted by calling pacmd set-sink-mute $SINK 0. But the button doesn't do that!

[Marco Chiappetta (mardurhack)]

The line "pacmd set-sink-mute $SINK 0" returns error:

>>> You need to specify a mute switch setting (0/1).

[Marco Chiappetta (mardurhack)]

Ok, this is definitely a big audio bug. This is what I've experienced (no headphones, max volume):

1) Run alsamixer and open some music/sound file.

2) Try to mute (press M) the Master Channel.

3) Unmute it (by pressing M again): nothing changes, still cannot hear anything (= XF86Mute).
3.1) Decrease and Increase the volume level of Speaker Channel: voila! The sound is up again!
3.2) Randomly mute Master, Speaker and/or Headphone Channels.
3.3) Exit from alsamixer and run it again: despite what you muted all the channels above are MUTED! This is NOT a correct behavior.
3.4) Unmute all of them and "touch" the volume level of the Speaker/Headphone Channel: the sound is back.

I've also noticed that the pulseaudio system isolates Headphones from Speaker. I mean that if I have 100% volume and then plug headphones in, the volume will change according to the last value set while headphones were plugged! And once I plug them out the volume level goes back to the "no-headphones" level. Now: I don't know if this behavior is wanted but Ubuntu does not implement it and, pheraps consequently, isn't affected from this bug.

@Rich Lawrence: I read the help of pacmd and successfully got a correct mute/unmute CLI shortcut. The problem now is: how do I replace the combo X86Mute with a dual "set-sink-mute 0 0/1" depending on the current state? Thanks in advance!