Report timing frames info in GetStats.

webrtc/video/receive_statistics_proxy.cc

Index: webrtc/video/receive_statistics_proxy.cc
diff --git a/webrtc/video/receive_statistics_proxy.cc b/webrtc/video/receive_statistics_proxy.cc
index 61b2ad13987aae3afb41f7aed304480b07e9b81f..b28210de1c35f7c19373aeea61f535811c229c1b 100644
--- a/webrtc/video/receive_statistics_proxy.cc
+++ b/webrtc/video/receive_statistics_proxy.cc
@@ -80,7 +80,8 @@ ReceiveStatisticsProxy::ReceiveStatisticsProxy(
       freq_offset_counter_(clock, nullptr, kFreqOffsetProcessIntervalMs),
       first_report_block_time_ms_(-1),
       avg_rtt_ms_(0),
-      last_content_type_(VideoContentType::UNSPECIFIED) {
+      last_content_type_(VideoContentType::UNSPECIFIED),
+      timing_frame_info_() {
   stats_.ssrc = config_.rtp.remote_ssrc;
   // TODO(brandtr): Replace |rtx_stats_| with a single instance of
   // StreamDataCounters.
@@ -371,6 +372,11 @@ VideoReceiveStream::Stats ReceiveStatisticsProxy::GetStats() const {
   stats_.decode_frame_rate = decode_fps_estimator_.Rate(now_ms).value_or(0);
   stats_.total_bitrate_bps =
       static_cast<int>(total_byte_tracker_.ComputeRate() * 8);
+  stats_.timing_frame_info = timing_frame_info_;
+  // Reset reported value to default, because default value will be always
+  // overwritten in |OnTimingFrameInfoUpdated|, thus allowing to store new
+  // value instead of reported one.
+  timing_frame_info_ = TimingFrameInfo();
   return stats_;
 }
 
@@ -432,6 +438,17 @@ void ReceiveStatisticsProxy::OnFrameBufferTimingsUpdated(
                        "ssrc", stats_.ssrc);
 }
 
+void ReceiveStatisticsProxy::OnTimingFrameInfoUpdated(
+    const TimingFrameInfo& info) {
+  rtc::CritScope lock(&crit_);
+  // Only the frame which was processed the longest since the last
+  // GetStats() call is reported. Therefore, only single 'longest' frame is
+  // stored.

[hbos, 2017/06/27 14:08:31]

Could we get the latest instead of the longest? Or something which does not rely
on "previous call to GetStats"?

[ilnik, 2017/06/27 15:23:56]

Can be simply latest, but this way we may loose important bit of information.
Outliers are more interesting for analysis. For each call we can report only a
single frame information. So we choose most interesting among all frames since
last call instead of latest.

[Taylor Brandstetter, 2017/06/28 07:27:46]

If I understand correctly, the whole motivation here is to find the outliers,
since they're the frames that end up increasing latency or causing frame drops.
And for those outliers, find out what parts of the pipeline are the bottlenecks
so they can be improved. With that in mind, this makes sense. It's more of a
debugging tool than a typical "stat", which justifies it not adhering to normal
GetStats conventions. If this interpretation is correct, it would be helpful if
the CL description and/or comments made this more clear, in case someone
encounters this code later without context.

[ilnik, 2017/06/29 08:39:56]

Done.

+  if (info.IsLongerThan(timing_frame_info_)) {
+    timing_frame_info_ = info;
+  }
+}
+
 void ReceiveStatisticsProxy::RtcpPacketTypesCounterUpdated(
     uint32_t ssrc,
     const RtcpPacketTypeCounter& packet_counter) {