Add experiment to disable ulpfec.

webrtc/video/video_send_stream.cc

 /*
  *  Copyright (c) 2013 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.
  */
 #include "webrtc/video/video_send_stream.h"
@@ skipping 969 matching lines @@
   const bool nack_enabled = config_->rtp.nack.rtp_history_ms > 0;
   int red_payload_type = config_->rtp.ulpfec.red_payload_type;
   int ulpfec_payload_type = config_->rtp.ulpfec.ulpfec_payload_type;
 
   // Shorthands.
   auto IsRedEnabled = [&]() { return red_payload_type >= 0; };
   auto DisableRed = [&]() { red_payload_type = -1; };
   auto IsUlpfecEnabled = [&]() { return ulpfec_payload_type >= 0; };
   auto DisableUlpfec = [&]() { ulpfec_payload_type = -1; };
 
+  if (webrtc::field_trial::IsEnabled("WebRTC-DisableUlpFecExperiment")) {
+    LOG(LS_INFO) << "Experiment to disable FlexFEC is enabled.";

[brandtr, 2017/08/23 14:10:44]

FlexFEC -> Ulpfec.

For clarity, mention that we only disable _sending_ Ulpfec. We will still
negotiate it, so we might still receive it.

[stefan-webrtc, 2017/08/23 14:27:08]

Done.

+    DisableUlpfec();
+  }
+
   // If enabled, FlexFEC takes priority over RED+ULPFEC.
   if (flexfec_enabled) {
     // We can safely disable RED here, because if the remote supports FlexFEC,
     // we know that it has a receiver without the RED/RTX workaround.
     // See http://crbug.com/webrtc/6650 for more information.
     if (IsRedEnabled()) {
       LOG(LS_INFO) << "Both FlexFEC and RED are configured. Disabling RED.";
       DisableRed();
     }
     if (IsUlpfecEnabled()) {
@@ skipping 38 matching lines @@
       DisableUlpfec();
     }
   }
 
   for (RtpRtcp* rtp_rtcp : rtp_rtcp_modules_) {
     // Set NACK.
     rtp_rtcp->SetStorePacketsStatus(
         true,
         kMinSendSidePacketHistorySize);
     // Set RED/ULPFEC information.
     for (RtpRtcp* rtp_rtcp : rtp_rtcp_modules_) {

[brandtr, 2017/08/23 14:10:44]

Not your change, but would you mind removing this unnecessary double loop? :)

[stefan-webrtc, 2017/08/23 14:27:08]

Yes!

       rtp_rtcp->SetUlpfecConfig(red_payload_type, ulpfec_payload_type);
     }
   }
 
   // Currently, both ULPFEC and FlexFEC use the same FEC rate calculation logic,
   // so enable that logic if either of those FEC schemes are enabled.
   protection_bitrate_calculator_.SetProtectionMethod(
       flexfec_enabled || IsUlpfecEnabled(), nack_enabled);
 }
 
@@ skipping 191 matching lines @@
       std::min(config_->rtp.max_packet_size,
                kPathMTU - transport_overhead_bytes_per_packet_);
 
   for (RtpRtcp* rtp_rtcp : rtp_rtcp_modules_) {
     rtp_rtcp->SetMaxRtpPacketSize(rtp_packet_size);
   }
 }
 
 }  // namespace internal
 }  // namespace webrtc