Add overhead to audio bwe min, max.

webrtc/media/engine/webrtcvoiceengine.cc

 /*
  *  Copyright (c) 2004 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 1402 matching lines @@
     RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
     if (stream_) {
       call_->DestroyAudioSendStream(stream_);
       stream_ = nullptr;
     }
     RTC_DCHECK(!stream_);
     if (webrtc::field_trial::FindFullName("WebRTC-Audio-SendSideBwe") ==
         "Enabled") {
       // TODO(mflodman): Keep testing this and set proper values.
       // Note: This is an early experiment currently only supported by Opus.
-      config_.min_bitrate_bps = kOpusMinBitrateBps;
-      config_.max_bitrate_bps = kOpusBitrateFbBps;
+      if (webrtc::field_trial::FindFullName(
+              "WebRTC-SendSideBwe-WithOverhead") == "Enabled") {
+        // TODO(michaelt): We should let the audio encoder decide which max/min
+        // bitrate he would prefer.

[minyue-webrtc, 2017/01/10 22:16:19]

he -> it

+
+        // OverheadPerPacket(58) = Ipv4(20B) + UDP(8B) + SRTP(10B) + RTP(12)
+        //     + RTP_ext(8);
+        // kMaxOverheadBps = OverheadPerPacket * 8 * 1000ms / frame_length(20ms)

[the sun, 2017/01/09 15:03:55]

nit: make the order
min
max
throughout the block.

[michaelt, 2017/01/09 15:56:57]

Done.

+        // kMinOverheadBps = OverheadPerPacket * 8 * 1000ms / frame_length(60ms)
+        constexpr int kMaxOverheadBps = 23200;
+        constexpr int kMinOverheadBps = 7733;
+        config_.min_bitrate_bps = kOpusMinBitrateBps + kMinOverheadBps;
+        config_.max_bitrate_bps = kOpusBitrateFbBps + kMaxOverheadBps;
+      } else {
+        config_.min_bitrate_bps = kOpusMinBitrateBps;
+        config_.max_bitrate_bps = kOpusBitrateFbBps;
+      }
     }
     stream_ = call_->CreateAudioSendStream(config_);
     RTC_CHECK(stream_);
     UpdateSendState();
   }
 
   rtc::ThreadChecker worker_thread_checker_;
   rtc::RaceChecker audio_capture_race_checker_;
   webrtc::AudioTransport* const voe_audio_transport_ = nullptr;
   webrtc::Call* call_ = nullptr;
@@ skipping 1203 matching lines @@
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   const auto it = send_streams_.find(ssrc);
   if (it != send_streams_.end()) {
     return it->second->channel();
   }
   return -1;
 }
 }  // namespace cricket
 
 #endif  // HAVE_WEBRTC_VOICE