Updated structures and functions for setting the max bitrate limit to take rtc::Optional<int>

webrtc/api/mediacontroller.cc

 /*
  *  Copyright 2015 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 45 matching lines @@
   }
   const cricket::MediaConfig& config() const override { return media_config_; }
 
  private:
   void Construct_w(cricket::MediaEngineInterface* media_engine) {
     RTC_DCHECK(worker_thread_->IsCurrent());
     RTC_DCHECK(media_engine);
     call_config_.audio_state = media_engine->GetAudioState();
     call_config_.bitrate_config.min_bitrate_bps = kMinBandwidthBps;
     call_config_.bitrate_config.start_bitrate_bps = kStartBandwidthBps;
-    call_config_.bitrate_config.max_bitrate_bps = kMaxBandwidthBps;
+    call_config_.bitrate_config.max_bitrate_bps =
+        rtc::Optional<int>(kMaxBandwidthBps);
   }

[pthatcher1, 2016/03/17 21:51:28]

Can this be unset?

If not, why have it be optional?

[skvlad, 2016/03/18 00:49:17]

This value will become unset if a video stream is added with no bitrate limit.
I'm not that familiar with the codebase, but the behavior seems to be like this:
1. The Call gets created, and the maximum bitrate limit for the BWE is set at 2
Mbps.
2. When a video stream gets created, the max bitrate from codec parameters - if
any - overrides this limit. If it is not set - which is probably the common case
- this will clear the max bitrate in the call.
3. If there is a b= parameter in the remote description, it will override the
bitrate limit from the codec.

This probably also means that for audio-only calls with no limit in SDP the
bandwidth will remain capped at 2 Mbps.

So in summary - it can and most likely will be unset after the call starts.

   void Close_w() {
     RTC_DCHECK(worker_thread_->IsCurrent());
     call_.reset();
   }
 
   rtc::Thread* const worker_thread_;
   const cricket::MediaConfig media_config_;
   cricket::ChannelManager* const channel_manager_;
   webrtc::Call::Config call_config_;
   rtc::scoped_ptr<webrtc::Call> call_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(MediaController);
 };
 }  // namespace {
 
 namespace webrtc {
 
 MediaControllerInterface* MediaControllerInterface::Create(
     const cricket::MediaConfig& config,
     rtc::Thread* worker_thread,
     cricket::ChannelManager* channel_manager) {
   return new MediaController(config, worker_thread, channel_manager);
 }
 }  // namespace webrtc