Add QP sum stats for received streams.

webrtc/video/receive_statistics_proxy.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 377 matching lines @@
   } else {
     auto it = rtx_stats_.find(ssrc);
     if (it != rtx_stats_.end()) {
       it->second = counters;
     } else {
       RTC_NOTREACHED() << "Unexpected stream ssrc: " << ssrc;
     }
   }
 }
 
-void ReceiveStatisticsProxy::OnDecodedFrame() {
+void ReceiveStatisticsProxy::OnDecodedFrame(int qp) {
   uint64_t now = clock_->TimeInMilliseconds();
 
   rtc::CritScope lock(&crit_);
   ++stats_.frames_decoded;
+  if (qp != -1) {

[sprang_webrtc, 2017/01/25 15:25:41]

Maybe we should dcheck on the off chance qp < -1 ?
Is 0 a valid value btw?

[sakal, 2017/01/25 15:34:45]

Sure, I can add that once we decide whether to use a integer or rtc::Optional. 0
is a valid value for all codecs.

[sakal, 2017/01/26 09:33:31]

Done.

+    if (!stats_.qp_sum) {
+      RTC_DCHECK_EQ(stats_.frames_decoded, 1);
+      stats_.qp_sum = rtc::Optional<uint64_t>(0);
+    }
+    *stats_.qp_sum += qp;
+  } else {
+    RTC_DCHECK(!stats_.qp_sum);

[sprang_webrtc, 2017/01/25 15:25:41]

Any chance we could hit this if we change codec on the fly, such as falling back
from hw to sw encoder or vice versa?

[sakal, 2017/01/25 15:34:45]

Yes, I think that is possible if one supports providing QP but another doesn't.
This is of course non-ideal. Maybe in these cases we should just remove qp_sum
stat? Any comments on this?

[sprang_webrtc, 2017/01/25 15:59:14]

Yeah, logging a warning and resetting the stats sounds like the right thing to
do then.

[sakal, 2017/01/26 09:33:31]

Done.

+  }
   decode_fps_estimator_.Update(1, now);
   stats_.decode_frame_rate = decode_fps_estimator_.Rate(now).value_or(0);
 }
 
 void ReceiveStatisticsProxy::OnRenderedFrame(const VideoFrame& frame) {
   int width = frame.width();
   int height = frame.height();
   RTC_DCHECK_GT(width, 0);
   RTC_DCHECK_GT(height, 0);
   uint64_t now = clock_->TimeInMilliseconds();
@@ skipping 70 matching lines @@
     return -1;
   return static_cast<int>(sum / num_samples);
 }
 
 void ReceiveStatisticsProxy::SampleCounter::Reset() {
   num_samples = 0;
   sum = 0;
 }
 
 }  // namespace webrtc