audio: reset mplayer's mute state when the system mixer volume changes

Before this commit, the mute state was only reset when either mute was
explicitly cleared, or the volume was changed via mplayer controls. If
the volume controls are connected to the system mixer, and the system
mixer volume is changed otherwise (e.g. with alsamixer), the mute
setting was inconsistent.

Avoid this by checking the volume. If the returned volume is not 0, the
mute flag is considered invalid. This relies on system mixers always
returning a volume of 0 when mplayer has set the volume 0.

Possible caveat: if the audio output's volume control don't return a
volume of exactly 0 after 0 was written, enabling mute basically won't
work. It will set the volume to silence, forget the previous volume, and
report that mute is disabled.

3 files changed, 26 insertions, 9 deletions

diff --git a/command.c b/command.c
index aee38463fd..414fd1e33b 100644
--- a/command.c
+++ b/command.c
@@ -763,14 +763,14 @@ static int mp_property_mute(m_option_t *prop, int action, void *arg,
         if (!arg)
             return M_PROPERTY_ERROR;
         mixer_setmuted(&mpctx->mixer, *(int *) arg);
-        mpctx->user_muted = mpctx->mixer.muted;
+        mpctx->user_muted = mixer_getmuted(&mpctx->mixer);
         return M_PROPERTY_OK;
     case M_PROPERTY_STEP_UP:
     case M_PROPERTY_STEP_DOWN:
         if (mpctx->edl_muted)
             return M_PROPERTY_DISABLED;
         mixer_mute(&mpctx->mixer);
-        mpctx->user_muted = mpctx->mixer.muted;
+        mpctx->user_muted = mixer_getmuted(&mpctx->mixer);
         return M_PROPERTY_OK;
     case M_PROPERTY_PRINT:
         if (!arg)
@@ -780,7 +780,8 @@ static int mp_property_mute(m_option_t *prop, int action, void *arg,
             return M_PROPERTY_OK;
         }
     default:
-        return m_property_flag(prop, action, arg, &mpctx->mixer.muted);
+        return m_property_flag_ro(prop, action, arg,
+                                  mixer_getmuted(&mpctx->mixer));
 
     }
 }
diff --git a/mixer.c b/mixer.c
index 4b99a6e967..61dc1dcb13 100644
--- a/mixer.c
+++ b/mixer.c
@@ -67,7 +67,7 @@ void mixer_uninit(mixer_t *mixer)
     // One complication is that the mute state should survive audio
     // reinitialization (e.g. when switching to a new file), so we have to be
     // sure mixer_reinit() will restore the mute state.
-    if (mixer->muted) {
+    if (mixer_getmuted(mixer)) {
         // avoid playing the rest of the audio buffer at restored volume
         ao_reset(mixer->ao);
         mixer_setmuted(mixer, false);
@@ -164,11 +164,17 @@ void mixer_getvolume(mixer_t *mixer, float *l, float *r)
     *l = 0;
     *r = 0;
     if (mixer->ao) {
+        float real_l, real_r;
+        internal_getvolume(mixer, &real_l, &real_r);
+        // consider the case when the system mixer volumes change independently
+        if (real_l != 0 || real_r != 0)
+            mixer->muted = false;
         if (mixer->muted) {
             *l = mixer->last_l;
             *r = mixer->last_r;
         } else {
-            internal_getvolume(mixer, l, r);
+            *l = real_l;
+            *r = real_r;
         }
     }
 }
@@ -199,14 +205,23 @@ void mixer_getbothvolume(mixer_t *mixer, float *b)
 
 void mixer_mute(mixer_t *mixer)
 {
-    mixer_setmuted(mixer, !mixer->muted);
+    mixer_setmuted(mixer, !mixer_getmuted(mixer));
+}
+
+bool mixer_getmuted(mixer_t *mixer)
+{
+    // this call will also check whether mute is still active, and "fix" it
+    float l, r;
+    mixer_getvolume(mixer, &l, &r);
+    return mixer->muted;
 }
 
 void mixer_setmuted(mixer_t *mixer, bool mute)
 {
-    if (mute == mixer->muted)
+    bool muted = mixer_getmuted(mixer);
+    if (mute == muted)
         return;
-    if (mixer->muted) {
+    if (muted) {
         mixer_setvolume(mixer, mixer->last_l, mixer->last_r);
     } else {
         mixer_getvolume(mixer, &mixer->last_l, &mixer->last_r);
diff --git a/mixer.h b/mixer.h
index f05688bc72..f99e860ff3 100644
--- a/mixer.h
+++ b/mixer.h
@@ -33,7 +33,7 @@ typedef struct mixer_s {
     struct ao *ao;
     af_stream_t *afilter;
     int volstep;
-    int muted;
+    bool muted;
     float last_l, last_r;
     float restore_vol_l, restore_vol_r;
     bool restore_volume;
@@ -49,6 +49,7 @@ void mixer_incvolume(mixer_t *mixer);
 void mixer_decvolume(mixer_t *mixer);
 void mixer_getbothvolume(mixer_t *mixer, float *b);
 void mixer_mute(mixer_t *mixer);
+bool mixer_getmuted(mixer_t *mixer);
 void mixer_setmuted(mixer_t *mixer, bool mute);
 void mixer_getbalance(mixer_t *mixer, float *bal);
 void mixer_setbalance(mixer_t *mixer, float bal);