FFmpegDemuxer should fall back to disabled streams for seeking

media/filters/ffmpeg_demuxer_unittest.cc

Index: media/filters/ffmpeg_demuxer_unittest.cc
diff --git a/media/filters/ffmpeg_demuxer_unittest.cc b/media/filters/ffmpeg_demuxer_unittest.cc
index 4225530af56ace84f41d510283508a68498d263f..f1e4a26ac51bee8da879463387dd92933c450e60 100644
--- a/media/filters/ffmpeg_demuxer_unittest.cc
+++ b/media/filters/ffmpeg_demuxer_unittest.cc
@@ -532,15 +532,22 @@ TEST_F(FFmpegDemuxerTest, Seeking_PreferredStreamSelection) {
   // prefer the video stream for seeking.
   EXPECT_EQ(video, preferred_seeking_stream(video_start_time));
 
-  // A disabled stream should not be preferred for seeking.
+  // A disabled stream should be preferred only when there's no other viable
+  // option among enabled streams.
   audio->set_enabled(false, base::TimeDelta());
-  EXPECT_EQ(video, preferred_seeking_stream(base::TimeDelta()));
-  EXPECT_EQ(video, preferred_seeking_stream(audio_start_time));
   EXPECT_EQ(video, preferred_seeking_stream(video_start_time));
+  // Audio stream is preferred, even though it is disabled, since video stream
+  // start time is higher than the seek target == audio_start_time in this case.
+  EXPECT_EQ(audio, preferred_seeking_stream(audio_start_time));
 
   audio->set_enabled(true, base::TimeDelta());
   video->set_enabled(false, base::TimeDelta());
-  EXPECT_EQ(audio, preferred_seeking_stream(base::TimeDelta()));
+  EXPECT_EQ(audio, preferred_seeking_stream(audio_start_time));
+  EXPECT_EQ(audio, preferred_seeking_stream(video_start_time));
+
+  // When both audio and video streams are disabled and there's no enabled
+  // streams, then audio is preferred since it has lower start time.
+  audio->set_enabled(false, base::TimeDelta());
   EXPECT_EQ(audio, preferred_seeking_stream(audio_start_time));
   EXPECT_EQ(audio, preferred_seeking_stream(video_start_time));
 }
@@ -1471,4 +1478,38 @@ TEST_F(FFmpegDemuxerTest, Read_Flac) {
   EXPECT_EQ(kSampleFormatS32, audio_config.sample_format());
 }
 
+// Verify that FFmpeg demuxer falls back to choosing disabled streams for
+// seeking if there's no suitable enabled stream found.
+TEST_F(FFmpegDemuxerTest, Seek_FallbackToDisabledVideoStream) {
+  // Input has only video stream, no audio.
+  CreateDemuxer("bear-320x240-video-only.webm");
+  InitializeDemuxer();
+  EXPECT_EQ(nullptr, demuxer_->GetStream(DemuxerStream::AUDIO));
+  DemuxerStream* vstream = demuxer_->GetStream(DemuxerStream::VIDEO);
+  EXPECT_NE(nullptr, vstream);
+  EXPECT_EQ(vstream, preferred_seeking_stream(base::TimeDelta()));
+
+  // Now pretend that video stream got disabled, e.g. due to current tab going
+  // into background.
+  vstream->set_enabled(false, base::TimeDelta());
+  // Since there's no other enabled streams, the preferred seeking stream should
+  // still be the video stream.
+  EXPECT_EQ(vstream, preferred_seeking_stream(base::TimeDelta()));
+}
+
+TEST_F(FFmpegDemuxerTest, Seek_FallbackToDisabledAudioStream) {
+  CreateDemuxer("bear-320x240-audio-only.webm");
+  InitializeDemuxer();
+  DemuxerStream* astream = demuxer_->GetStream(DemuxerStream::AUDIO);
+  EXPECT_NE(nullptr, astream);
+  EXPECT_EQ(nullptr, demuxer_->GetStream(DemuxerStream::VIDEO));
+  EXPECT_EQ(astream, preferred_seeking_stream(base::TimeDelta()));
+
+  // Now pretend that audio stream got disabled.
+  astream->set_enabled(false, base::TimeDelta());
+  // Since there's no other enabled streams, the preferred seeking stream should
+  // still be the audio stream.
+  EXPECT_EQ(astream, preferred_seeking_stream(base::TimeDelta()));
+}
+
 }  // namespace media