Try AVSEEK_FLAG_ANY if _BACKWARD fails.

We usually want to do _BACKWARD as this should seek to the keyframe
before the seek position.  On some files this fails, and then it
seems that _ANY is a good next thing to try.

3 files changed, 33 insertions, 7 deletions

diff --git a/run/tests b/run/tests
index b5f45d5e7..8f6b2d3e2 100755
--- a/run/tests
+++ b/run/tests
@@ -3,7 +3,7 @@
 # e.g. --run_tests=foo
 set -e
 
-PRIVATE_GIT="81e32cb5962320333839b7020d14d9f291b8ff2d"
+PRIVATE_GIT="e92043f43b024812f2b5f8c8faed159a15a87aaf"
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 source $DIR/environment
diff --git a/src/lib/ffmpeg_decoder.cc b/src/lib/ffmpeg_decoder.cc
index ebbc242e3..c70733c4c 100644
--- a/src/lib/ffmpeg_decoder.cc
+++ b/src/lib/ffmpeg_decoder.cc
@@ -431,12 +431,19 @@ FFmpegDecoder::seek (ContentTime time, bool accurate)
 	if (u < ContentTime ()) {
 		u = ContentTime ();
 	}
-	av_seek_frame (
-		_format_context,
-		stream.get(),
-		u.seconds() / av_q2d (_format_context->streams[stream.get()]->time_base),
-		AVSEEK_FLAG_BACKWARD
-		);
+
+	auto seek = [&](int flag) {
+		return av_seek_frame(
+			_format_context,
+			stream.get(),
+			u.seconds() / av_q2d (_format_context->streams[stream.get()]->time_base),
+			flag
+			);
+	};
+
+	if (seek(AVSEEK_FLAG_BACKWARD) < 0) {
+		DCPOMATIC_ASSERT(seek(AVSEEK_FLAG_ANY) >= 0);
+	};
 
 	/* Force re-creation of filter graphs to reset them, to make sure
 	   they don't have any pre-seek frames.
diff --git a/test/ffmpeg_decoder_seek_test.cc b/test/ffmpeg_decoder_seek_test.cc
index 43967e458..ee0da99da 100644
--- a/test/ffmpeg_decoder_seek_test.cc
+++ b/test/ffmpeg_decoder_seek_test.cc
@@ -133,3 +133,22 @@ BOOST_AUTO_TEST_CASE(ffmpeg_decoder_seek_test)
 		}
 	    );
 }
+
+
+BOOST_AUTO_TEST_CASE(seek_when_backward_fails)
+{
+	auto content = make_shared<FFmpegContent>(TestPaths::private_data() / "strange_keyframes.mp4");
+	auto film = new_test_film("seek_when_backward_fails", { content });
+	auto decoder = make_shared<FFmpegDecoder>(film, content, false);
+	decoder->video->Data.connect(bind(&store, _1));
+
+	/* Due to a bug this seek would fail silently, giving us different frame each time */
+	for (auto i = 0; i < 3; ++i) {
+		decoder->seek(dcpomatic::ContentTime(), true);
+		stored = {};
+		while (!decoder->pass() && !stored) {}
+		BOOST_REQUIRE(static_cast<bool>(stored));
+		BOOST_CHECK(stored->time == dcpomatic::ContentTime());
+	}
+}
+