mixer, libao: add proper mute control

The mixer frontend code can now make use of a proper system mixer mute
toggle, if the audio output driver supports it.

The consequence is that, if support is available, mplayer will no longer
temporarily set the system volume to 0 if mute is enabled.

Generally, the code now deals with the following combinations of available
AO features:
- software volume control forced by user (--softvol / soft_vol flag)
  => if enabled, never touch the "hardware" controls
- "hardware"/driver volume control available (whether
  AOCONTROL_GET/SET_VOLUME works)
  => if not available, enable volume controls by enabling softvol
- "hardware"/driver mute control (AOCONTROL_GET/SET_MUTE)
  => if not available, emulate by setting volume to 0
- whether the volume+mute controls are kept or not when the AO is closed
  (indicated by ao->no_persistent_volume)
  => if not persistent, restore the volume/mute next time the AO is opened

0 files changed, 0 insertions, 0 deletions