Add a 2-frame `delay' on content arriving at the player to give

subtitle content the chance to catch up.  Fixes problems observed
when overlaying a DCP subtitle onto an existing DCP and then seeking
into the first subtitle.  After the seek the decoder positions were:

DCP: 0.
subtitle: first subtitle time.

This causes the DCP decoder to be pass()ed first and so the subtitle
for the video frame has not arrived yet.

I hope this does not cause unpredicted side effects...

1 files changed, 43 insertions, 0 deletions

diff --git a/src/lib/delay.h b/src/lib/delay.h
new file mode 100644
index 000000000..fa08b0558
--- /dev/null
+++ b/src/lib/delay.h
@@ -0,0 +1,43 @@
+/*
+    Copyright (C) 2018 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#ifndef DCPOMATIC_DELAY_H
+#define DCPOMATIC_DELAY_H
+
+#include "types.h"
+#include "video_adjuster.h"
+#include "content_video.h"
+#include <boost/signals2.hpp>
+
+class Piece;
+
+/** A class which `delays' received video by 2 frames; i.e. when it receives
+ *  a video frame it emits the last-but-one it received.
+ */
+class Delay : public VideoAdjuster
+{
+public:
+	void video (boost::weak_ptr<Piece>, ContentVideo video);
+
+private:
+	boost::optional<ContentVideo> _last;
+};
+
+#endif