libhb: fix potential pgs timestamp problem

Under rare circumstances, the computed start time would jump backward.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5753 b64f7644-9d1e-0410-96f1-a4d463321fa5

1 files changed, 20 insertions, 1 deletions

diff --git a/libhb/decpgssub.c b/libhb/decpgssub.c
index 3c6c8fe90..f6004cb6d 100644
--- a/libhb/decpgssub.c
+++ b/libhb/decpgssub.c
@@ -282,12 +282,31 @@ static int decsubWork( hb_work_object_t * w, hb_buffer_t ** buf_in,
             // work around broken timestamps
             if (pts < 0 && in->s.start >= 0)
             {
-                pts = in->s.start;
+                if (pts < pv->last_pts)
+                {
+                    // XXX: this should only happen if the prevous pts
+                    // was unknown and our 3 second default duration
+                    // overshot the next pgs pts.
+                    //
+                    // assign a 1 second duration
+                    pts = pv->last_pts + 1 * 90000LL;
+                    hb_log("[warning] decpgssub: track %d, non-monotically increasing PTS",
+                           w->subtitle->out_track);
+                }
+                else
+                {
+                    pts = in->s.start;
+                }
             }
             else if (pts < 0)
             {
                 // XXX: a broken pts will cause us to drop this subtitle,
                 //      which is bad; use a default duration of 3 seconds
+                //
+                //      A broken pts is only generated when a pgs packet
+                //      occurs after a discontinuity and before the
+                //      next audio or video packet which re-establishes
+                //      timing (afaik).
                 pts = pv->last_pts + 3 * 90000LL;
                 hb_log("[warning] decpgssub: track %d, invalid PTS",
                        w->subtitle->out_track);