Add framerate to VideoSinkWants and ability to signal on overuse

webrtc/media/base/videosourceinterface.h

 /*
  *  Copyright (c) 2016 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 16 matching lines @@
   bool black_frames = false;
 
   // Tells the source the maximum number of pixels the sink wants.
   rtc::Optional<int> max_pixel_count;
   // Tells the source the desired number of pixels the sinks wants. This will
   // typically be used when stepping the resolution up again when conditions
   // have improved after an earlier downgrade. The source should select the
   // closest resolution to this pixel count, but if max_pixel_count is set, it
   // still sets the absolute upper bound.
   rtc::Optional<int> target_pixel_count;
+  // Tells the source the maximum framerate the sink wants.
+  rtc::Optional<int> max_framerate_fps_;

[nisse-webrtc, 2017/03/08 08:08:54]

Consider changing it to non-optional with default value,

  int max_framerate_fps_ = std::numeric_limits<int>::max();

Could do the same to max_pixel_count, of course.

That would simplify the logic in several places.

[kthelgason, 2017/03/08 08:15:59]

I endorse this comment!

[sprang_webrtc, 2017/03/09 13:19:34]

It might simplify it in some places, like videobroadcaster.
It will make it uglier in others, where we'll have to change
  if (!foo.max_framerate_fps_)
to
  if (foo_max_framerate_fps_ == std::numeric_limits<int>::max())

I suggest we save this for an impending overhaul of the entire struct.

 };
 
 template <typename VideoFrameT>
 class VideoSourceInterface {
  public:
   virtual void AddOrUpdateSink(VideoSinkInterface<VideoFrameT>* sink,
                                const VideoSinkWants& wants) = 0;
   // RemoveSink must guarantee that at the time the method returns,
   // there is no current and no future calls to VideoSinkInterface::OnFrame.
   virtual void RemoveSink(VideoSinkInterface<VideoFrameT>* sink) = 0;
 
  protected:
   virtual ~VideoSourceInterface() {}
 };
 
 }  // namespace rtc
 #endif  // WEBRTC_MEDIA_BASE_VIDEOSOURCEINTERFACE_H_