Split subtitles at reel boundaries (#1918).

3 files changed, 49 insertions, 6 deletions

diff --git a/src/lib/reel_writer.cc b/src/lib/reel_writer.cc
index ad52a1ca1..184707373 100644
--- a/src/lib/reel_writer.cc
+++ b/src/lib/reel_writer.cc
@@ -868,11 +868,12 @@ ReelWriter::write (PlayerText subs, TextType type, optional<DCPTextTrack> track,
 		DCPOMATIC_ASSERT (false);
 	}
 
-	auto const vfr = film()->video_frame_rate();
+	/* timecode rate for subtitles we emit; we might as well stick to ms accuracy here, I think */
+	auto const tcr = 1000;
 
 	for (auto i: subs.string) {
-		i.set_in  (dcp::Time(period.from.seconds() - _period.from.seconds(), vfr));
-		i.set_out (dcp::Time(period.to.seconds() - _period.from.seconds(), vfr));
+		i.set_in  (dcp::Time(period.from.seconds() - _period.from.seconds(), tcr));
+		i.set_out (dcp::Time(period.to.seconds() - _period.from.seconds(), tcr));
 		asset->add (make_shared<dcp::SubtitleString>(i));
 	}
 
@@ -880,8 +881,8 @@ ReelWriter::write (PlayerText subs, TextType type, optional<DCPTextTrack> track,
 		asset->add (
 			make_shared<dcp::SubtitleImage>(
 				i.image->as_png(),
-				dcp::Time(period.from.seconds() - _period.from.seconds(), vfr),
-				dcp::Time(period.to.seconds() - _period.from.seconds(), vfr),
+				dcp::Time(period.from.seconds() - _period.from.seconds(), tcr),
+				dcp::Time(period.to.seconds() - _period.from.seconds(), tcr),
 				i.rectangle.x, dcp::HAlign::LEFT, i.rectangle.y, dcp::VAlign::TOP,
 				dcp::Time(), dcp::Time()
 				)
diff --git a/src/lib/writer.cc b/src/lib/writer.cc
index ad588f0a6..4386b8e26 100644
--- a/src/lib/writer.cc
+++ b/src/lib/writer.cc
@@ -545,6 +545,7 @@ Writer::finish (boost::filesystem::path output_dcp)
 	LOG_GENERAL_NC ("Finishing ReelWriters");
 
 	for (auto& i: _reels) {
+		write_hanging_text (i);
 		i.finish (output_dcp);
 	}
 
@@ -798,6 +799,23 @@ Writer::write (PlayerText text, TextType type, optional<DCPTextTrack> track, DCP
 	while ((*reel)->period().to <= period.from) {
 		++(*reel);
 		DCPOMATIC_ASSERT (*reel != _reels.end());
+		write_hanging_text (**reel);
+	}
+
+	if (period.to > (*reel)->period().to) {
+		/* This text goes off the end of the reel.  Store parts of it that should go into
+		 * other reels.
+		 */
+		for (auto i = std::next(*reel); i != _reels.end(); ++i) {
+			auto overlap = i->period().overlap(period);
+			if (overlap) {
+				_hanging_texts.push_back (HangingText{text, type, track, *overlap});
+			}
+		}
+		/* Back off from the reel boundary by a couple of frames to avoid tripping checks
+		 * for subtitles being too close together.
+		 */
+		period.to = (*reel)->period().to - DCPTime::from_frames(2, film()->video_frame_rate());
 	}
 
 	(*reel)->write (text, type, track, period);
@@ -907,3 +925,17 @@ Writer::calculate_referenced_digests (boost::function<void (float)> set_progress
 	}
 }
 
+
+void
+Writer::write_hanging_text (ReelWriter& reel)
+{
+	vector<HangingText> new_hanging_texts;
+	for (auto i: _hanging_texts) {
+		if (i.period.from == reel.period().from) {
+			reel.write (i.text, i.type, i.track, i.period);
+		} else {
+			new_hanging_texts.push_back (i);
+		}
+	}
+	_hanging_texts = new_hanging_texts;
+}
diff --git a/src/lib/writer.h b/src/lib/writer.h
index 14d4b7faa..aab7d5fc7 100644
--- a/src/lib/writer.h
+++ b/src/lib/writer.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2020 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2021 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -129,6 +129,7 @@ private:
 	void set_digest_progress (Job* job, float progress);
 	void write_cover_sheet (boost::filesystem::path output_dcp);
 	void calculate_referenced_digests (boost::function<void (float)> set_progress);
+	void write_hanging_text (ReelWriter& reel);
 
 	std::weak_ptr<Job> _job;
 	std::vector<ReelWriter> _reels;
@@ -204,4 +205,13 @@ private:
 	bool _have_subtitles = false;
 	/** all closed caption tracks that we have on any reel */
 	std::set<DCPTextTrack> _have_closed_captions;
+
+	struct HangingText {
+		PlayerText text;
+		TextType type;
+		boost::optional<DCPTextTrack> track;
+		dcpomatic::DCPTimePeriod period;
+	};
+
+	std::vector<HangingText> _hanging_texts;
 };