Public bug reported:
Most IBM / Lenovo Thinkpads have hardware volume control with apropriate
buttons above the keyboard (volume up, down and mute). Gnome in Ubuntu
is configured in such a way, that the keypresses are trapped (this is
correct), apropriate volume window is displayed (correct) and Gnome
volume control is modified. Last step is actually wrong - the keys in
Thinkpads control the volume hardware directly, so every keypress turns
the volume up/down regardless of sound card settings (in Ubuntu case -
this would be Alsa mixer). Current behaviour results in volume being
changed twice - for example if I press the volume up button, I get
volume reduction via Gnome sound mixer plus volume reduction via
hardware control. Effectively this creates an exponential (and not
linear as it should be) volume change. In short - it is very difficult
to control volume, especially relatively quiet sounds, with volume keys
only.
The "patch" solution is to decouple Gnome mixer from hardware buttons.
Of course it could be done manually, by deleting apropriate key actions
in System->Preferences->Keyboard shortcuts, but this also disables
windows showing volume. A better thing (but more complex) would involve
reading /proc/acpi/ibm/volume and displaying the volume window according
to this value at each volume button keypress.
I tested this on T21, T42 and Thinkpad 600. I guess only some R series
notebooks (R31 etc.) would not be affected, as these do not have hardware mixer.
Steps to reproduce:
1. Press hardware volume key (eg. volume up) on a Thinkpad
2. Observe the volume change - it is changed in hardware mixer (correct) and in
Gnome volume control (incorrect)
** Affects: Ubuntu
Importance: Untriaged
Status: Unconfirmed
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Wrong handling of volume buttons on IBM Thinkpad notebooks
https://launchpad.net/bugs/51537
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