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

1 files changed, 1 insertions, 0 deletions

diff --git a/mixer.h b/mixer.h
index f99e860ff3..6619783a58 100644
--- a/mixer.h
+++ b/mixer.h
@@ -34,6 +34,7 @@ typedef struct mixer_s {
     af_stream_t *afilter;
     int volstep;
     bool muted;
+    bool mute_emulation;
     float last_l, last_r;
     float restore_vol_l, restore_vol_r;
     bool restore_volume;