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authorwm4 <wm4@nowhere>2013-08-14 13:23:37 +0200
committerwm4 <wm4@nowhere>2013-08-15 23:43:36 +0200
commitda76eb9f14dcb7a361dd817aa3d18c4c319b432a (patch)
tree12f496ab0396f2a3fd96de36c39ff07dfb392be5
parentdf6901b65315b4c75e7e18ce00049706c076e2fb (diff)
downloadmpv-da76eb9f14dcb7a361dd817aa3d18c4c319b432a.tar.bz2
mpv-da76eb9f14dcb7a361dd817aa3d18c4c319b432a.tar.xz
sub: fix accidental subtitle overlaps
The fix_overlaps_and_gaps() function in dec_sub.c fixes small gaps or overlaps between subtitle events. However, sometimes it could happen that the corrected subtitle events could overlap by 1ms due to bad rounding, making libass shift subtitles to reduce collisions. (The second subtitle will be shown above the previous one, even if both subtitles are visible only for 1ms.) sd_ass.c rounds the timestamps when converting to integers for unknown reasons. I think it would work fine without that rounding, but since I have no clue why it rounds, and since it could be needed to ensure correct timestamps with ASS subtitles demuxed from Matroska, I'd rather not touch it. So the solution is to use already rounded timestamps to calculate the new subtitle duration in fix_overlaps_and_gaps(). See github issue #182.
-rw-r--r--sub/dec_sub.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/sub/dec_sub.c b/sub/dec_sub.c
index 8622d2c872..998cb0db7f 100644
--- a/sub/dec_sub.c
+++ b/sub/dec_sub.c
@@ -302,6 +302,8 @@ static void multiply_timings(struct packet_list *subs, double factor)
}
}
+#define MS_TS(f_ts) ((int)((f_ts) * 1000 + 0.5))
+
// Remove overlaps and fill gaps between adjacent subtitle packets. This is done
// by adjusting the duration of the earlier packet. If the gaps or overlap are
// larger than the threshold, or if the durations are close to the threshold,
@@ -322,7 +324,10 @@ static void fix_overlaps_and_gaps(struct packet_list *subs)
if (fabs(next->pts - end) <= threshold && cur->duration >= keep &&
next->duration >= keep)
{
- cur->duration = next->pts - cur->pts;
+ // Conceptually: cur->duration = next->pts - cur->pts;
+ // But make sure the rounding and conversion to integers in
+ // sd_ass.c can't produce overlaps.
+ cur->duration = (MS_TS(next->pts) - MS_TS(cur->pts)) / 1000.0;
}
}
}