audio: add AO_INIT_MEDIA_ROLE_MUSIC

This allows the AO to set the media role directly during init().

audio/out/ao.h

@@ -56,6 +56,8 @@ enum {
     AO_INIT_STREAM_SILENCE = 1 << 2,
     // Force exclusive mode, i.e. lock out the system mixer.
     AO_INIT_EXCLUSIVE = 1 << 3,
+    // Initialize with music role.
+    AO_INIT_MEDIA_ROLE_MUSIC = 1 << 4,
 };
 
 struct ao_device_desc {

player/audio.c

@@ -190,6 +190,20 @@ void update_playback_speed(struct MPContext *mpctx)
     update_speed_filters(mpctx);
 }
 
+static bool has_video_track(struct MPContext *mpctx)
+{
+    if (mpctx->vo_chain && mpctx->vo_chain->is_coverart)
+        return false;
+
+    for (int n = 0; n < mpctx->num_tracks; n++) {
+        struct track *track = mpctx->tracks[n];
+        if (track->type == STREAM_VIDEO && !track->attached_picture && !track->image)
+            return true;
+    }
+
+    return false;
+}
+
 static void ao_chain_reset_state(struct ao_chain *ao_c)
 {
     ao_c->last_out_pts = MP_NOPTS_VALUE;
@@ -416,6 +430,9 @@ static int reinit_audio_filters_and_output(struct MPContext *mpctx)
                           opts->audio_output_channels.num_chmaps);
     }
 
+    if (!has_video_track(mpctx))
+        ao_flags |= AO_INIT_MEDIA_ROLE_MUSIC;
+
     mpctx->ao_filter_fmt = out_fmt;
 
     mpctx->ao = ao_init_best(mpctx->global, ao_flags, mp_wakeup_core_cb,