basesink: Only drop buffer if their PTS is out of segment

As of now, even for stream completly inside segment, there is no
guarantied that the DTS will be inside the segment. Specifically
for H.264 with B-Frames, the first few frames often have DTS that
are before the segment.

Instead of using the sync timestamp to clip out of segment buffer,
take the duration from the start/stop provided by the sub-class, and
check if the pts and pts_end is out of segment.

https://bugzilla.gnome.org/show_bug.cgi?id=752791

diff --git a/libs/gst/base/gstbasesink.c b/libs/gst/base/gstbasesink.c
index cd759ac..f5fea82 100644 (file)
--- a/libs/gst/base/gstbasesink.c
+++ b/libs/gst/base/gstbasesink.c
@@ -3400,10 +3400,21 @@ gst_base_sink_chain_unlocked (GstBaseSink * basesink, GstPad * pad,
   GST_DEBUG_OBJECT (basesink, "got times start: %" GST_TIME_FORMAT
       ", end: %" GST_TIME_FORMAT, GST_TIME_ARGS (start), GST_TIME_ARGS (end));
 
-  /* a dropped buffer does not participate in anything */
+  /* a dropped buffer does not participate in anything. Buffer can only be
+   * dropped if their PTS falls completly outside the segment, while we sync
+   * preferably on DTS */
   if (GST_CLOCK_TIME_IS_VALID (start) && (segment->format == GST_FORMAT_TIME)) {
+    GstClockTime pts = GST_BUFFER_PTS (sync_buf);
+    GstClockTime pts_end = GST_CLOCK_TIME_NONE;
+
+    if (!GST_CLOCK_TIME_IS_VALID (pts))
+      pts = start;
+
+    if (GST_CLOCK_TIME_IS_VALID (end))
+      pts_end = pts + (end - start);
+
     if (G_UNLIKELY (!gst_segment_clip (segment,
-                GST_FORMAT_TIME, start, end, NULL, NULL)))
+                GST_FORMAT_TIME, pts, pts_end, NULL, NULL)))
       goto out_of_segment;
   }