Add histogram stats for AV sync stream offset:

webrtc/video/video_receive_stream.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 362 matching lines @@
 
   // Post processing is not supported if the frame is backed by a texture.
   if (video_frame->native_handle() == NULL) {
     if (config_.pre_render_callback)
       config_.pre_render_callback->FrameCallback(video_frame);
   }
 }
 
 int VideoReceiveStream::RenderFrame(const uint32_t /*stream_id*/,
                                     const VideoFrame& video_frame) {
+  int64_t sync_offset_ms;
+  if (vie_sync_.GetStreamSyncOffsetInMs(video_frame, &sync_offset_ms))
+    stats_proxy_.OnSyncOffsetUpdated(sync_offset_ms);

[stefan-webrtc, 2016/03/09 15:59:30]

Nice, thanks!

I wonder if we instead should expose the current playout time in NTP in
GetStats()? In that case it would be possible for the user to compute the sync
offset to any stream, instead of us choosing what (audio) stream to compare with
here. What do you think? I think that is probably a later improvement either
way, since that would require that we implement that stat for audio too...

[åsapersson, 2016/03/10 09:08:35]

Sounds good. Maybe as a later improvement?

[stefan-webrtc, 2016/03/10 14:25:09]

Yes

+
   // TODO(pbos): Wire up config_.render->IsTextureSupported() and convert if not
   // supported. Or provide methods for converting a texture frame in
   // VideoFrame.
 
   if (config_.renderer != nullptr)
     config_.renderer->RenderFrame(
         video_frame,
         video_frame.render_time_ms() - clock_->TimeInMilliseconds());
 
   stats_proxy_.OnRenderedFrame(video_frame);
@@ skipping 26 matching lines @@
   return true;
 }
 
 void VideoReceiveStream::Decode() {
   static const int kMaxDecodeWaitTimeMs = 50;
   vcm_->Decode(kMaxDecodeWaitTimeMs);
 }
 
 }  // namespace internal
 }  // namespace webrtc