Reduce seek-inducing slack in SubtitleDecoder; see comment.

diff --git a/src/lib/subtitle_decoder.cc b/src/lib/subtitle_decoder.cc
index d20196a63597f41a768e1aa7e1b98ab7c52010f0..5336686165d6dc12dbe94a1b15fb237f42dbafcf 100644 (file)
--- a/src/lib/subtitle_decoder.cc
+++ b/src/lib/subtitle_decoder.cc
@@ -62,8 +62,15 @@ SubtitleDecoder::get (list<T> const & subs, list<ContentTimePeriod> const & sp,
                return list<T> ();
        }
 
-       /* Seek if what we want is before what we have, or more than a reasonable amount after */
-       if (subs.empty() || sp.back().to < subs.front().period().from || sp.front().from > (subs.back().period().to + ContentTime::from_seconds (5))) {
+       /* Seek if what we want is before what we have, or a more than a little bit after.
+          Be careful with the length of this `little bit'; consider the case where the last
+          subs were just less than this little bit B ago.  Then we will not seek, but instead
+          pass() for nearly B seconds; if we are a FFmpegDecoder then this will generate B's
+          worth of video which will stack up.  If B + the pre-roll is bigger than the maximum
+          number of frames that the VideoDecoder will keep then we will get an assertion
+          failure in VideoDecoder.
+       */
+       if (subs.empty() || sp.back().to < subs.front().period().from || sp.front().from > (subs.back().period().to + ContentTime::from_seconds (1))) {
                seek (sp.front().from, true);
        }