video: remove another redundant wakeup

The wakeup at the end of VO frame rendering seems redundant, because
after rendering almost no state changes. The player core can queue a new
frame once frame rendering begins, and there's a separate wakeup for
this. The only thing that actually changes is in->rendering. The only
thing that seems to depend on it and can trigger a wakeup is the
vo_still_displaying() function. Change it so that it needs an explicit
call to a new API function, so we can avoid wakeups in the common case.

The vo_still_displaying() code is mostly just moved around due to
locking and for avoiding forward declarations.

Also a somewhat risky change (tasty new bugs).

player/video.c

@@ -1108,8 +1108,10 @@ void write_video(struct MPContext *mpctx)
     struct mp_image_params p = mpctx->next_frames[0]->params;
     if (!vo->params || !mp_image_params_equal(&p, vo->params)) {
         // Changing config deletes the current frame; wait until it's finished.
-        if (vo_still_displaying(vo))
+        if (vo_still_displaying(vo)) {
+            vo_request_wakeup_on_done(vo);
             return;
+        }
 
         const struct vo_driver *info = mpctx->video_out->driver;
         char extra[20] = {0};

video/out/vo.c

@@ -128,6 +128,7 @@ struct vo_internal {
     bool want_redraw;               // redraw request from VO to player
     bool send_reset;                // send VOCTRL_RESET
     bool paused;
+    bool wakeup_on_done;
     int queued_events;              // event mask for the user
     int internal_events;            // event mask for us
 
@@ -747,6 +748,41 @@ void vo_wakeup(struct vo *vo)
     pthread_mutex_unlock(&in->lock);
 }
 
+static bool still_displaying(struct vo *vo)
+{
+    struct vo_internal *in = vo->in;
+    int64_t now = mp_time_us();
+    int64_t frame_end = 0;
+    if (in->current_frame) {
+        frame_end = in->current_frame->pts + MPMAX(in->current_frame->duration, 0);
+        if (in->current_frame->display_synced)
+            frame_end = in->current_frame->num_vsyncs > 0 ? INT64_MAX : 0;
+    }
+    return (now < frame_end || in->rendering || in->frame_queued) && in->hasframe;
+}
+
+// Return true if there is still a frame being displayed (or queued).
+bool vo_still_displaying(struct vo *vo)
+{
+    pthread_mutex_lock(&vo->in->lock);
+    bool res = still_displaying(vo);
+    pthread_mutex_unlock(&vo->in->lock);
+    return res;
+}
+
+// Make vo issue a wakeup once vo_still_displaying() becomes true.
+void vo_request_wakeup_on_done(struct vo *vo)
+{
+    struct vo_internal *in = vo->in;
+    pthread_mutex_lock(&vo->in->lock);
+    if (still_displaying(vo)) {
+        in->wakeup_on_done = true;
+    } else {
+        wakeup_core(vo);
+    }
+    pthread_mutex_unlock(&vo->in->lock);
+}
+
 // Whether vo_queue_frame() can be called. If the VO is not ready yet, the
 // function will return false, and the VO will call the wakeup callback once
 // it's ready.
@@ -897,6 +933,7 @@ static bool render_frame(struct vo *vo)
 
     if (in->dropped_frame) {
         in->drop_count += 1;
+        wakeup_core(vo);
     } else {
         in->rendering = true;
         in->hasframe_rendered = true;
@@ -952,13 +989,17 @@ static bool render_frame(struct vo *vo)
     }
 
     pthread_cond_broadcast(&in->wakeup); // for vo_wait_frame()
-    wakeup_core(vo);
 
     got_frame = true;
 
 done:
     talloc_free(frame);
+    if (in->wakeup_on_done && !still_displaying(vo)) {
+        in->wakeup_on_done = false;
+        wakeup_core(vo);
+    }
     pthread_mutex_unlock(&in->lock);
+
     return got_frame || (in->frame_queued && in->frame_queued->display_synced);
 }
 
@@ -1146,24 +1187,6 @@ void vo_seek_reset(struct vo *vo)
     pthread_mutex_unlock(&in->lock);
 }
 
-// Return true if there is still a frame being displayed (or queued).
-// If this returns true, a wakeup some time in the future is guaranteed.
-bool vo_still_displaying(struct vo *vo)
-{
-    struct vo_internal *in = vo->in;
-    pthread_mutex_lock(&vo->in->lock);
-    int64_t now = mp_time_us();
-    int64_t frame_end = 0;
-    if (in->current_frame) {
-        frame_end = in->current_frame->pts + MPMAX(in->current_frame->duration, 0);
-        if (in->current_frame->display_synced)
-            frame_end = in->current_frame->num_vsyncs > 0 ? INT64_MAX : 0;
-    }
-    bool working = now < frame_end || in->rendering || in->frame_queued;
-    pthread_mutex_unlock(&vo->in->lock);
-    return working && in->hasframe;
-}
-
 // Whether at least 1 frame was queued or rendered since last seek or reconfig.
 bool vo_has_frame(struct vo *vo)
 {

video/out/vo.h

@@ -485,6 +485,7 @@ bool vo_is_ready_for_frame(struct vo *vo, int64_t next_pts);
 void vo_queue_frame(struct vo *vo, struct vo_frame *frame);
 void vo_wait_frame(struct vo *vo);
 bool vo_still_displaying(struct vo *vo);
+void vo_request_wakeup_on_done(struct vo *vo);
 bool vo_has_frame(struct vo *vo);
 void vo_redraw(struct vo *vo);
 bool vo_want_redraw(struct vo *vo);