Adding OnReceivedOverhead to AudioEncoder.

webrtc/modules/audio_coding/codecs/audio_encoder.cc

Index: webrtc/modules/audio_coding/codecs/audio_encoder.cc
diff --git a/webrtc/modules/audio_coding/codecs/audio_encoder.cc b/webrtc/modules/audio_coding/codecs/audio_encoder.cc
index 956c4e086f0dbf244cb348ad93083d19ad252411..fb147b9df8a9cb520a7ceb2fa76ca7dd3421fd9c 100644
--- a/webrtc/modules/audio_coding/codecs/audio_encoder.cc
+++ b/webrtc/modules/audio_coding/codecs/audio_encoder.cc
@@ -12,6 +12,7 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/trace_event.h"
+#include "webrtc/system_wrappers/include/field_trial.h"
 
 namespace webrtc {
 
@@ -24,6 +25,9 @@ AudioEncoder::EncodedInfo& AudioEncoder::EncodedInfo::operator=(
 AudioEncoder::EncodedInfo& AudioEncoder::EncodedInfo::operator=(EncodedInfo&&) =
     default;
 
+AudioEncoder::AudioEncoder() = default;
+AudioEncoder::~AudioEncoder() = default;
+
 int AudioEncoder::RtpTimestampRateHz() const {
   return SampleRateHz();
 }
@@ -82,11 +86,26 @@ void AudioEncoder::OnReceivedUplinkPacketLossFraction(
 }
 
 void AudioEncoder::OnReceivedTargetAudioBitrate(int target_audio_bitrate_bps) {
-  SetTargetBitrate(target_audio_bitrate_bps);
+  if (webrtc::field_trial::FindFullName("WebRTC-SendSideBwe-WithOverhead") ==
+      "Enabled") {
+    if (!overhead_bytes_per_packet_) {
+      // Ignore the target bitrate is overhead is unknown.
+      return;
+    }
+    int overhead_rate =
+        8 * 1000 * *overhead_bytes_per_packet_ / Num10MsFramesInNextPacket();

[michaelt, 2016/11/24 13:55:18]

I think this calculation is wrong by a a factor of 10 :) .
A unittest for this would be nice.

+    SetTargetBitrate(std::max(0, target_audio_bitrate_bps - overhead_rate));
+  } else {
+    SetTargetBitrate(target_audio_bitrate_bps);
+  }
 }
 
 void AudioEncoder::OnReceivedRtt(int rtt_ms) {}
 
+void AudioEncoder::OnReceivedOverhead(size_t overhead_bytes_per_packet) {
+  overhead_bytes_per_packet_ = rtc::Optional<size_t>(overhead_bytes_per_packet);
+}
+
 void AudioEncoder::SetReceiverFrameLengthRange(int min_frame_length_ms,
                                                int max_frame_length_ms) {}