Improve rejection of "crazy" frame rates (#2238).

Firstly, look for other video streams even if one is not suitable.
Secondly, ignore very low frame rates as well as very high ones.

2 files changed, 16 insertions, 5 deletions

diff --git a/src/lib/ffmpeg.cc b/src/lib/ffmpeg.cc
index a54b4fc01..6c8509b6c 100644
--- a/src/lib/ffmpeg.cc
+++ b/src/lib/ffmpeg.cc
@@ -149,6 +149,11 @@ FFmpeg::setup_general ()
 	for (uint32_t i = 0; i < _format_context->nb_streams; ++i) {
 		auto s = _format_context->streams[i];
 		if (s->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && avcodec_find_decoder(s->codecpar->codec_id)) {
+			auto const frame_rate = av_q2d(s->avg_frame_rate);
+			if (frame_rate < 1 || frame_rate > 1000) {
+				/* Ignore video streams with crazy frame rates.  These are usually things like album art on MP3s. */
+				continue;
+			}
 			if (s->avg_frame_rate.num > 0 && s->avg_frame_rate.den > 0) {
 				/* This is definitely our video stream */
 				_video_stream = i;
@@ -166,11 +171,6 @@ FFmpeg::setup_general ()
 		_video_stream = video_stream_undefined_frame_rate.get();
 	}
 
-	/* Ignore video streams with crazy frame rates.  These are usually things like album art on MP3s. */
-	if (_video_stream && av_q2d(av_guess_frame_rate(_format_context, _format_context->streams[_video_stream.get()], 0)) > 1000) {
-		_video_stream = optional<int>();
-	}
-
 	/* Hack: if the AVStreams have duplicate IDs, replace them with our
 	   own.  We use the IDs so that we can cope with VOBs, in which streams
 	   move about in index but remain with the same ID in different
diff --git a/test/ffmpeg_examiner_test.cc b/test/ffmpeg_examiner_test.cc
index 2c244f541..9dfb0f3dc 100644
--- a/test/ffmpeg_examiner_test.cc
+++ b/test/ffmpeg_examiner_test.cc
@@ -83,3 +83,14 @@ BOOST_AUTO_TEST_CASE (ffmpeg_examiner_mkv_test)
 	auto content = make_shared<FFmpegContent>(TestPaths::private_data() / "sample.mkv");
 	auto examiner = make_shared<FFmpegExaminer>(content);
 }
+
+
+/** Check that the video stream is correctly picked from a difficult file (#2238) */
+BOOST_AUTO_TEST_CASE (ffmpeg_examiner_video_stream_selection_test)
+{
+	auto content = make_shared<FFmpegContent>(TestPaths::private_data() / "isy.mp4");
+	auto examiner = make_shared<FFmpegExaminer>(content);
+
+	BOOST_REQUIRE (examiner->video_frame_rate());
+	BOOST_CHECK_EQUAL (examiner->video_frame_rate().get(), 25);
+}