vf_vavpp: use future instead of past PTS to determine field duration

If the deinterlacer separates fields, the framerate must be doubled.
Since we have no stable and reliably framerate anywhere, we've been
calculating it by taking the time halfway to the next frame.

vf_vavpp actually used the past frame to calculate the frame duration,
which is sort of ok, but will skip the 2nd field in a stream (since the
first frame has no past PTS). This is annoying for testing, so use the
future frame PTS instead, which means the last field of the stream will
be dropped instead.

1 files changed, 7 insertions, 7 deletions

diff --git a/video/filter/refqueue.c b/video/filter/refqueue.c
index 1103be9afa..64c5b9b03b 100644
--- a/video/filter/refqueue.c
+++ b/video/filter/refqueue.c
@@ -27,7 +27,6 @@ struct mp_refqueue {
     int needed_future_frames;
 
     bool eof;
-    double past_pts;
 
     // Queue of input frames, used to determine past/current/future frames.
     // queue[0] is the newest frame, queue[num_queue - 1] the oldest.
@@ -54,7 +53,7 @@ void mp_refqueue_set_refs(struct mp_refqueue *q, int past, int future)
 {
     assert(past >= 0 && future >= 0);
     q->needed_past_frames = past;
-    q->needed_future_frames = future;
+    q->needed_future_frames = MPMAX(future, 1); // at least 1 for determining PTS
 }
 
 // Discard all state.
@@ -65,7 +64,6 @@ void mp_refqueue_flush(struct mp_refqueue *q)
     q->num_queue = 0;
     q->pos = -1;
     q->eof = false;
-    q->past_pts = MP_NOPTS_VALUE;
 }
 
 // Add a new frame to the queue. (Call mp_refqueue_next() to advance the
@@ -101,8 +99,6 @@ void mp_refqueue_next(struct mp_refqueue *q)
     if (!mp_refqueue_has_output(q))
         return;
 
-    q->past_pts = q->queue[q->pos]->pts;
-
     q->pos--;
 
     assert(q->pos >= -1 && q->pos < q->num_queue);
@@ -141,10 +137,14 @@ double mp_refqueue_get_field_pts(struct mp_refqueue *q, int field)
     if (field == 0 || pts == MP_NOPTS_VALUE)
         return pts;
 
-    if (q->past_pts == MP_NOPTS_VALUE)
+    if (q->pos == 0)
+        return MP_NOPTS_VALUE;
+
+    double next_pts = q->queue[q->pos - 1]->pts;
+    if (next_pts == MP_NOPTS_VALUE)
         return MP_NOPTS_VALUE;
 
-    double frametime = pts - q->past_pts;
+    double frametime = next_pts - pts;
     if (frametime <= 0.0 || frametime >= 1.0)
         return MP_NOPTS_VALUE;