Set AVDISCARD_ALL flag for disabled streams in FFmpegDemuxer

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 d0a7d1a2565d94d598310d1952984f73171272b7..3cfb72f70ebb62a5bdaf6e92df6dbf162d1939f7 100644
--- a/media/filters/ffmpeg_demuxer_unittest.cc
+++ b/media/filters/ffmpeg_demuxer_unittest.cc
@@ -83,11 +83,14 @@ class FFmpegDemuxerTest : public testing::Test {
  protected:
   FFmpegDemuxerTest() {}
 
-  virtual ~FFmpegDemuxerTest() {
+  virtual ~FFmpegDemuxerTest() { Shutdown(); }
+
+  void Shutdown() {
     if (demuxer_)
       demuxer_->Stop();
     demuxer_.reset();
     base::RunLoop().RunUntilIdle();
+    data_source_.reset();
   }
 
   void CreateDemuxer(const std::string& name) {
@@ -267,6 +270,12 @@ class FFmpegDemuxerTest : public testing::Test {
     EXPECT_TRUE(got_eos_buffer);
   }
 
+  void Seek(base::TimeDelta seek_target) {
+    WaitableMessageLoopEvent event;
+    demuxer_->Seek(seek_target, event.GetPipelineStatusCB());
+    event.RunAndWaitForStatus(PIPELINE_OK);
+  }
+
  private:
   void CreateDataSource(const std::string& name) {
     CHECK(!data_source_);
@@ -800,6 +809,71 @@ TEST_F(FFmpegDemuxerTest, Read_AudioNegativeStartTimeAndOpusSfxDiscard_Sync) {
   }
 }
 
+TEST_F(FFmpegDemuxerTest, Read_DiscardDisabledVideoStream) {
+  // Verify that disabling the video stream properly marks it as AVDISCARD_ALL
+  // in FFmpegDemuxer. The AVDISCARD_ALL flag allows FFmpeg to ignore key frame
+  // requirements for the disabled stream and thus allows to select the seek
+  // position closer to the |seek_target|, resulting in less data being read
+  // from the data source.
+  // The input file bear-vp8-webvtt.webm has key video frames at 1.602s and at
+  // 2.002s. If we want to seek to 2.0s position while the video stream is
+  // enabled, then FFmpeg is forced to start reading from 1.602s, which is the
+  // earliest position guaranteed to give us key frames for all enabled streams.
+  // But when the video stream is disabled, FFmpeg can start reading from 1.987s
+  // which is earliest audio key frame before the 2.0s |seek_target|.
+  const base::TimeDelta seek_target = base::TimeDelta::FromMilliseconds(2000);
+
+  CreateDemuxer("bear-vp8-webvtt.webm");
+  InitializeDemuxer();
+  Seek(seek_target);
+  GetStream(DemuxerStream::AUDIO)
+      ->Read(NewReadCB(FROM_HERE, 163, 1612000, true));
+  base::RunLoop().Run();
+  auto bytes_read_with_video_enabled = data_source_->bytes_read_for_testing();
+
+  static_cast<FFmpegDemuxerStream*>(GetStream(DemuxerStream::VIDEO))
+      ->set_enabled(false, base::TimeDelta());
+  data_source_->reset_bytes_read_for_testing();
+  Seek(seek_target);
+  GetStream(DemuxerStream::AUDIO)
+      ->Read(NewReadCB(FROM_HERE, 156, 1987000, true));
+  base::RunLoop().Run();
+  auto bytes_read_with_video_disabled = data_source_->bytes_read_for_testing();
+  EXPECT_LT(bytes_read_with_video_disabled, bytes_read_with_video_enabled);
+}
+
+TEST_F(FFmpegDemuxerTest, Read_DiscardDisabledTextStream) {
+  // This test case reads the same video frame twice, first with the text track
+  // enabled, then with the text track disabled. When the text track is
+  // disabled, FFmpegDemuxer sets the AVDISCARD_ALL flag on the corresponding
+  // stream, which allows FFmpeg to choose the initial reading position closer
+  // to the requested video frame (i.e. closer to seek_target), since it doesn't
+  // need to consider key frames for the text stream. This results in less data
+  // being read compared to the case with enabled text track.
+  const base::TimeDelta seek_target = base::TimeDelta::FromMilliseconds(805);
+
+  CreateDemuxer("bear-vp8-webvtt.webm");
+  EXPECT_CALL(host_, AddTextStream(_, _));
+  InitializeDemuxerWithText();
+  Seek(seek_target);
+  GetStream(DemuxerStream::VIDEO)
+      ->Read(NewReadCB(FROM_HERE, 5425, 801000, true));
+  base::RunLoop().Run();
+  auto bytes_read_with_text_enabled = data_source_->bytes_read_for_testing();
+
+  Shutdown();
+
+  CreateDemuxer("bear-vp8-webvtt.webm");
+  InitializeDemuxer();
+  Seek(seek_target);
+  GetStream(DemuxerStream::VIDEO)
+      ->Read(NewReadCB(FROM_HERE, 5425, 801000, true));
+  base::RunLoop().Run();
+  auto bytes_read_with_text_disabled = data_source_->bytes_read_for_testing();
+
+  EXPECT_LT(bytes_read_with_text_disabled, bytes_read_with_text_enabled);
+}
+
 TEST_F(FFmpegDemuxerTest, Read_EndOfStream) {
   // Verify that end of stream buffers are created.
   CreateDemuxer("bear-320x240.webm");