Add histogram stats for average QP per frame for VP9 (for sent video streams):

webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc

 /*
  *  Copyright (c) 2014 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 676 matching lines @@
 
   CodecSpecificInfo codec_specific;
   PopulateCodecSpecific(&codec_specific, *pkt, input_image_->timestamp());
 
   if (encoded_image_._length > 0) {
     TRACE_COUNTER1("webrtc", "EncodedFrameSize", encoded_image_._length);
     encoded_image_._timeStamp = input_image_->timestamp();
     encoded_image_.capture_time_ms_ = input_image_->render_time_ms();
     encoded_image_._encodedHeight = raw_->d_h;
     encoded_image_._encodedWidth = raw_->d_w;
+    int qp = -1;
+    vpx_codec_control(encoder_, VP8E_GET_LAST_QUANTIZER, &qp);

[mflodman, 2016/04/11 07:00:23]

I assume VP8 is the correct parameter here, but just checking.

[åsapersson, 2016/04/11 07:28:15]

Think so, it says that it is supported for VP9.

+    encoded_image_.qp_ = qp;
     encoded_complete_callback_->Encoded(encoded_image_, &codec_specific,
                                         &frag_info);
   }
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 vpx_svc_ref_frame_config VP9EncoderImpl::GenerateRefsAndFlags(
     const SuperFrameRefSettings& settings) {
   static const vpx_enc_frame_flags_t kAllFlags =
       VP8_EFLAG_NO_REF_ARF | VP8_EFLAG_NO_REF_GF | VP8_EFLAG_NO_REF_LAST |
@@ skipping 272 matching lines @@
   frame_buffer_pool_.ClearPool();
   inited_ = false;
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
 const char* VP9DecoderImpl::ImplementationName() const {
   return "libvpx";
 }
 
 }  // namespace webrtc