vo: fix audio-timing framedrop regressions

Commit 12eb8b2d accidentally disabled framedropping in the audio timing
case. It tried to replace the last_flip field with the prev_vsync one,
which didn't work because prev_sync is reset to 0 if the timing code is
used. Fix it by always setting it properly. This field must (or should)
be reinitialized to something sensible when switching to display sync
timing mode; since prev_vsync is not reset anymore, the check when to
reinitialize this field has to be adjusted as well.

It's a bit weird that update_vsync_timing_after_swap() now does some
minor work for timing mode too, but I guess it's ok, if only to avoid
additional fields and timer calls.

1 files changed, 5 insertions, 4 deletions

diff --git a/video/out/vo.c b/video/out/vo.c
index 808f543f1f..c117e5fccf 100644
--- a/video/out/vo.c
+++ b/video/out/vo.c
@@ -325,7 +325,6 @@ static void reset_vsync_timings(struct vo *vo)
     struct vo_internal *in = vo->in;
     in->num_vsync_samples = 0;
     in->drop_point = 0;
-    in->prev_vsync = 0;
     in->estimated_vsync_interval = 0;
     in->estimated_vsync_jitter = -1;
     in->base_vsync = 0;
@@ -348,12 +347,14 @@ static void update_vsync_timing_after_swap(struct vo *vo)
 {
     struct vo_internal *in = vo->in;
 
-    if (!in->expecting_vsync || !in->prev_vsync) {
+    int64_t now = mp_time_us();
+
+    if (!in->expecting_vsync) {
+        in->prev_vsync = now; // for normal system-time framedrop
         reset_vsync_timings(vo);
         return;
     }
 
-    int64_t now = mp_time_us();
     int max_samples = 200;
     if (in->num_vsync_samples >= max_samples)
         in->num_vsync_samples -= 1;
@@ -764,7 +765,7 @@ static bool render_frame(struct vo *vo)
         in->current_frame->num_vsyncs -= 1;
 
     in->expecting_vsync = in->current_frame->display_synced && !in->paused;
-    if (in->expecting_vsync && !in->prev_vsync)
+    if (in->expecting_vsync && !in->num_vsync_samples) // first DS frame in a row
         in->prev_vsync = mp_time_us();
 
     if (in->dropped_frame) {