Get VideoCapturer stats via VideoTrackSourceInterface in StatsCollector,

webrtc/api/mediastreaminterface.h

 /*
  *  Copyright 2012 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 69 matching lines @@
                                   public NotifierInterface {
  public:
   enum TrackState {
     kLive,
     kEnded,
   };
 
   static const char kAudioKind[];
   static const char kVideoKind[];
 
+  // The kind() method must return kAudioKind only if the object is a
+  // subclass of AudioTrackInterface, and kVideoKind only if the
+  // object is a subclass of VideoTrackInterface. It is typically used
+  // to protect a static_cast<> to the corresponding subclass.
   virtual std::string kind() const = 0;
   virtual std::string id() const = 0;
   virtual bool enabled() const = 0;
   virtual TrackState state() const = 0;
   virtual bool set_enabled(bool enable) = 0;
 
  protected:
   virtual ~MediaStreamTrackInterface() {}
 };
 
 // VideoTrackSourceInterface is a reference counted source used for VideoTracks.
 // The same source can be used in multiple VideoTracks.
 class VideoTrackSourceInterface
     : public MediaSourceInterface,
       public rtc::VideoSourceInterface<cricket::VideoFrame> {
  public:
+  struct Stats {
+    // Original frame size, before video adaptation.
+    int input_width;
+    int input_height;
+  };
   // Get access to the source implementation of cricket::VideoCapturer.
   // This can be used for receiving frames and state notifications.
   // But it should not be used for starting or stopping capturing.
   // TODO(perkj): We are currently trying to replace all internal use of
   // cricket::VideoCapturer with rtc::VideoSourceInterface. Once that
   // refactoring is done,
   // remove this method.
   virtual cricket::VideoCapturer* GetVideoCapturer() = 0;
 
   virtual void Stop() = 0;
   virtual void Restart() = 0;
 
   // Indicates that parameters suitable for screencasts should be automatically
   // applied to RtpSenders.
   // TODO(perkj): Remove these once all known applications have moved to
   // explicitly setting suitable parameters for screencasts and dont' need this
   // implicit behavior.
   virtual bool is_screencast() const = 0;
 
   // Indicates that the encoder should denoise the video before encoding it.
   // TODO(perkj): Remove this once denoising is done by the source, and not by
   // the encoder.
   virtual bool needs_denoising() const = 0;
 
+  virtual bool GetStats(Stats* stats) = 0;

[pbos-webrtc, 2016/03/31 11:50:46]

I assume this is intended to fail if we haven't gotten a first frame? Can you
document when GetStats would be expected to fail?

Otherwise: Can this be void instead?

[perkj_webrtc, 2016/03/31 11:57:30]

prefer void.

[nisse-webrtc, 2016/03/31 12:07:27]

What should a VideoTrackSource (used for remote sources) do then?

[nisse-webrtc, 2016/03/31 12:07:27]

It's intended to fail if the source doesn't have any stats. In particular, a
remote source will always return false.

[perkj_webrtc, 2016/03/31 12:13:31]

I see. Ok - please then document when this returns true/false.

+
  protected:
   virtual ~VideoTrackSourceInterface() {}
 };
 
 class VideoTrackInterface
     : public MediaStreamTrackInterface,
       public rtc::VideoSourceInterface<cricket::VideoFrame> {
  public:
   // Register a video sink for this track.
   void AddOrUpdateSink(rtc::VideoSinkInterface<cricket::VideoFrame>* sink,
@@ skipping 123 matching lines @@
   virtual bool RemoveTrack(AudioTrackInterface* track) = 0;
   virtual bool RemoveTrack(VideoTrackInterface* track) = 0;
 
  protected:
   virtual ~MediaStreamInterface() {}
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_MEDIASTREAMINTERFACE_H_