Fix incorrect timing of PNG subtitles in second and subsequent reels.

Backported from 5728b8095b9522626d61b1c684a9492f759e2870 in v2.15.x.

4 files changed, 91 insertions, 2 deletions

diff --git a/src/lib/reel_writer.cc b/src/lib/reel_writer.cc
index 3b9e413a2..b7ccc07ce 100644
--- a/src/lib/reel_writer.cc
+++ b/src/lib/reel_writer.cc
@@ -619,8 +619,8 @@ ReelWriter::write (PlayerText subs, TextType type, optional<DCPTextTrack> track,
 			shared_ptr<dcp::Subtitle>(
 				new dcp::SubtitleImage(
 					i.image->as_png(),
-					dcp::Time(period.from.seconds(), _film->video_frame_rate()),
-					dcp::Time(period.to.seconds(), _film->video_frame_rate()),
+					dcp::Time(period.from.seconds() - _period.from.seconds(), _film->video_frame_rate()),
+					dcp::Time(period.to.seconds() - _period.from.seconds(), _film->video_frame_rate()),
 					i.rectangle.x, dcp::HALIGN_LEFT, i.rectangle.y, dcp::VALIGN_TOP,
 					dcp::Time(), dcp::Time()
 					)
diff --git a/test/data b/test/data
-Subproject e5257e5721bde4d182f8317373030a1d99fbff9
+Subproject eda45cf0736a897f944a8c38e9aed9ca98d4c3c
diff --git a/test/subtitle_reel_test.cc b/test/subtitle_reel_test.cc
new file mode 100644
index 000000000..7a722b460
--- /dev/null
+++ b/test/subtitle_reel_test.cc
@@ -0,0 +1,88 @@
+/*
+    Copyright (C) 2019 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/>.
+
+*/
+
+#include "lib/film.h"
+#include "lib/image_content.h"
+#include "lib/dcp_subtitle_content.h"
+#include "lib/video_content.h"
+#include "test.h"
+#include <dcp/dcp.h>
+#include <dcp/cpl.h>
+#include <dcp/reel.h>
+#include <dcp/interop_subtitle_asset.h>
+#include <dcp/reel_subtitle_asset.h>
+#include <boost/test/unit_test.hpp>
+
+using std::list;
+using boost::shared_ptr;
+
+/* Check that timings are done correctly for multi-reel DCPs with PNG subs */
+BOOST_AUTO_TEST_CASE (subtitle_reel_test)
+{
+	shared_ptr<Film> film = new_test_film2 ("subtitle_reel_test");
+	film->set_interop (true);
+	shared_ptr<ImageContent> red_a (new ImageContent("test/data/flat_red.png"));
+	shared_ptr<ImageContent> red_b (new ImageContent("test/data/flat_red.png"));
+	shared_ptr<DCPSubtitleContent> sub_a (new DCPSubtitleContent("test/data/png_subs/subs.xml"));
+	shared_ptr<DCPSubtitleContent> sub_b (new DCPSubtitleContent("test/data/png_subs/subs.xml"));
+
+	film->examine_and_add_content (red_a);
+	film->examine_and_add_content (red_b);
+	film->examine_and_add_content (sub_a);
+	film->examine_and_add_content (sub_b);
+
+	BOOST_REQUIRE (!wait_for_jobs());
+
+	red_a->set_position (film, dcpomatic::DCPTime());
+	red_a->video->set_length (240);
+	sub_a->set_position (film, dcpomatic::DCPTime());
+	red_b->set_position (film, dcpomatic::DCPTime::from_seconds(10));
+	red_b->video->set_length (240);
+	sub_b->set_position (film, dcpomatic::DCPTime::from_seconds(10));
+
+	film->set_reel_type (REELTYPE_BY_VIDEO_CONTENT);
+
+	film->make_dcp ();
+	BOOST_REQUIRE (!wait_for_jobs());
+
+	dcp::DCP dcp ("build/test/subtitle_reel_test/" + film->dcp_name());
+	dcp.read ();
+	BOOST_REQUIRE_EQUAL (dcp.cpls().size(), 1);
+	shared_ptr<dcp::CPL> cpl = dcp.cpls().front();
+
+	list<shared_ptr<dcp::Reel> > reels = cpl->reels ();
+	BOOST_REQUIRE_EQUAL (reels.size(), 2);
+	list<shared_ptr<dcp::Reel> >::const_iterator i = reels.begin ();
+	BOOST_REQUIRE ((*i)->main_subtitle());
+	BOOST_REQUIRE ((*i)->main_subtitle()->asset());
+	shared_ptr<dcp::InteropSubtitleAsset> A = boost::dynamic_pointer_cast<dcp::InteropSubtitleAsset>((*i)->main_subtitle()->asset());
+	BOOST_REQUIRE (A);
+	++i;
+	BOOST_REQUIRE ((*i)->main_subtitle());
+	BOOST_REQUIRE ((*i)->main_subtitle()->asset());
+	shared_ptr<dcp::InteropSubtitleAsset> B = boost::dynamic_pointer_cast<dcp::InteropSubtitleAsset>((*i)->main_subtitle()->asset());
+	BOOST_REQUIRE (B);
+
+	BOOST_REQUIRE_EQUAL (A->subtitles().size(), 1);
+	BOOST_REQUIRE_EQUAL (B->subtitles().size(), 1);
+
+	/* These times should be the same as they are should be offset from the start of the reel */
+	BOOST_CHECK (A->subtitles().front()->in() == B->subtitles().front()->in());
+}
diff --git a/test/wscript b/test/wscript
index 8059ae2d3..5e7634ea3 100644
--- a/test/wscript
+++ b/test/wscript
@@ -106,6 +106,7 @@ def build(bld):
                  ssa_subtitle_test.cc
                  stream_test.cc
                  subtitle_charset_test.cc
+                 subtitle_reel_test.cc
                  subtitle_reel_number_test.cc
                  subtitle_trim_test.cc
                  test.cc