Special case when packet->pos==-1

Sometimes video containers report audio packet timestamps as -1,
which was triggering the packet drop code from background track seeking.

Bug: 902634
Change-Id: I2b74fde01f9f2e06aeaf5fa4c2a3a1a4af8ead5d
Reviewed-on: https://chromium-review.googlesource.com/c/1352579
Commit-Queue: Ted Meyer <tmathmeyer@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611923}

media/filters/ffmpeg_demuxer.cc

@@ -382,13 +382,19 @@ void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
   // video frame dropping is handled by the renderer when correcting for a/v
   // sync.
   if (is_audio && !fixup_chained_ogg_ && last_packet_pos_ != AV_NOPTS_VALUE) {
+    // Some containers have unknown position...
+    if (packet->pos == -1)
+      packet->pos = last_packet_pos_;
+
     if (packet->pos < last_packet_pos_) {
-      DVLOG(3) << "Dropped packet with out of order position";
+      DVLOG(3) << "Dropped packet with out of order position (" << packet->pos
+               << " < " << last_packet_pos_ << ")";
       return;
     }
     if (packet->pos == last_packet_pos_ && packet_dts <= last_packet_dts_) {
       DCHECK_NE(last_packet_dts_, AV_NOPTS_VALUE);
-      DVLOG(3) << "Dropped packet with out of order display timestamp";
+      DVLOG(3) << "Dropped packet with out of order display timestamp ("
+               << packet_dts << " < " << last_packet_dts_ << ")";
       return;
     }
   }
@@ -405,7 +411,7 @@ void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
     if (packet->flags & AV_PKT_FLAG_KEY)
       waiting_for_keyframe_ = false;
     else {
-      DVLOG(3) << "Dropped non-keyframe pts=" << packet->pts;
+      DLOG(WARNING) << "Dropped non-keyframe pts=" << packet->pts;
       return;
     }
   }

media/filters/ffmpeg_demuxer_unittest.cc

@@ -748,7 +748,7 @@ TEST_F(FFmpegDemuxerTest, Read_AudioNegativeStartTimeAndOggDiscard_Sync) {
     event.RunAndWaitForStatus(PIPELINE_OK);
   }
 }
-#endif
+#endif  // !defined(OS_ANDROID)
 
 // Similar to the test above, but using an opus clip with a large amount of
 // pre-skip, which ffmpeg encodes as negative timestamps.
@@ -797,6 +797,30 @@ TEST_F(FFmpegDemuxerTest, Read_AudioNegativeStartTimeAndOpusDiscard_Sync) {
 }
 
 #if BUILDFLAG(USE_PROPRIETARY_CODECS)
+
+#if defined(OS_CHROMEOS)
+TEST_F(FFmpegDemuxerTest, TestAudioNegativeTimestamps) {
+  // Note: This test will _crash_ the browser if negative timestamp
+  // values are skipped, since this file is heavily truncated to avoid
+  // copyright issue. If the negative timestamp packets are dropped, the
+  // demuxer will continue to read off the end of the stream.
+  CreateDemuxer("negative-audio-timestamps.avi");
+  InitializeDemuxer();
+
+  DemuxerStream* audio = GetStream(DemuxerStream::AUDIO);
+  audio->Read(NewReadCB(FROM_HERE, 104, 0, true));
+  base::RunLoop().Run();
+  audio->Read(NewReadCB(FROM_HERE, 104, 25873, true));
+  base::RunLoop().Run();
+  audio->Read(NewReadCB(FROM_HERE, 104, 51746, true));
+  base::RunLoop().Run();
+  audio->Read(NewReadCB(FROM_HERE, 104, 77619, true));
+  base::RunLoop().Run();
+  audio->Read(NewReadCB(FROM_HERE, 104, 103492, true));
+  base::RunLoop().Run();
+}
+#endif  // defined(OS_CHROMEOS)
+
 // Similar to the test above, but using an opus clip plus h264 b-frames to
 // ensure we don't apply chained ogg workarounds to other content.
 TEST_F(FFmpegDemuxerTest,
@@ -847,7 +871,7 @@ TEST_F(FFmpegDemuxerTest,
     event.RunAndWaitForStatus(PIPELINE_OK);
   }
 }
-#endif
+#endif  // BUILDFLAG(USE_PROPRIETARY_CODECS)
 
 // Similar to the test above, but using sfx-opus.ogg, which has a much smaller
 // amount of discard padding and no |start_time| set on the AVStream.

media/test/data/README.md

@@ -46,6 +46,9 @@ bear-vp8-webvtt.webm as a 'subt' handler type.
 Just the first initialization segment of bear-1280x720_av_frag.mp4, modified to
 have the mvhd version 0 32-bit duration field set to all 1's.
 
+#### media/test/data/negative-audio-timestamps.avi
+A truncated audio/video file with audio packet timestamps of -1. We need to ensure that these packets arent dropped.
+
 ### FLAC
 
 #### bear-flac.mp4