Cherry-pick e881184: fix incorrect subtitle positioning in a VF when there are more than two consecutive reels without subtitles.

2 files changed, 4 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 66d010b6d..2ac3da72e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,7 +4,8 @@
 
 2018-05-15  Carl Hetherington  <cth@carlh.net>
 
-	* Version 2.12.5 released.
+	* Fix incorrect subtitle positining in a VF when there are more than
+	two consecutive reels with no subtitles.
 
 2018-05-08  Carl Hetherington  <cth@carlh.net>
 
diff --git a/src/lib/writer.cc b/src/lib/writer.cc
index deb93b6c1..5f25b23c5 100644
--- a/src/lib/writer.cc
+++ b/src/lib/writer.cc
@@ -657,8 +657,9 @@ Writer::write (PlayerSubtitles subs, DCPTimePeriod period)
 		return;
 	}
 
-	if (_subtitle_reel->period().to <= period.from) {
+	while (_subtitle_reel->period().to <= period.from) {
 		++_subtitle_reel;
+		DCPOMATIC_ASSERT (_subtitle_reel != _reels.end());
 	}
 
 	_subtitle_reel->write (subs);