Reduce VideoSendStream recreations due to FlexFEC.

webrtc/media/engine/webrtcvideoengine2.cc

 /*
  *  Copyright (c) 2014 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 25 matching lines @@
 #include "webrtc/media/engine/webrtcvideoencoderfactory.h"
 #include "webrtc/media/engine/webrtcvoiceengine.h"
 #include "webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter.h"
 #include "webrtc/system_wrappers/include/field_trial.h"
 
 using DegradationPreference = webrtc::VideoSendStream::DegradationPreference;
 
 namespace cricket {
 namespace {
 // If this field trial is enabled, we will enable sending FlexFEC and disable
-// sending ULPFEC whenever the former has been negotiated.
-// FlexFEC can only be negotiated when the "flexfec-03" SDP codec is enabled,
-// which is done by enabling the "WebRTC-FlexFEC-03-Advertised" field trial; see
-// internalencoderfactory.cc.
+// sending ULPFEC whenever the former has been negotiated in the SDPs.
 bool IsFlexfecFieldTrialEnabled() {
   return webrtc::field_trial::IsEnabled("WebRTC-FlexFEC-03");
 }
 
+// If this field trial is enabled, the "flexfec-03" codec may have been
+// advertised as being supported in the local SDP. That means that we must be
+// ready to receive FlexFEC packets. See internalencoderfactory.cc.
+bool IsFlexfecAdvertisedFieldTrialEnabled() {
+  return webrtc::field_trial::IsEnabled("WebRTC-FlexFEC-03-Advertised");
+}
+
 // If this field trial is enabled, we will report VideoContentType RTP extension
 // in capabilities (thus, it will end up in the default SDP and extension will
 // be sent for all key-frames).
 bool IsVideoContentTypeExtensionFieldTrialEnabled() {
   return webrtc::field_trial::IsEnabled("WebRTC-VideoContentTypeExtension");
 }
 
 // Wrap cricket::WebRtcVideoEncoderFactory as a webrtc::VideoEncoderFactory.
 class EncoderFactoryAdapter : public webrtc::VideoEncoderFactory {
  public:
@@ skipping 634 matching lines @@
 
 bool WebRtcVideoChannel2::GetChangedSendParameters(
     const VideoSendParameters& params,
     ChangedSendParameters* changed_params) const {
   if (!ValidateCodecFormats(params.codecs) ||
       !ValidateRtpExtensions(params.extensions)) {
     return false;
   }
 
   // Select one of the remote codecs that will be used as send codec.
-  const rtc::Optional<VideoCodecSettings> selected_send_codec =
+  rtc::Optional<VideoCodecSettings> selected_send_codec =
       SelectSendVideoCodec(MapCodecs(params.codecs));
 
   if (!selected_send_codec) {
     LOG(LS_ERROR) << "No video codecs supported.";
     return false;
   }
 
+  // Never enable sending FlexFEC, unless we are in the experiment.
+  if (!IsFlexfecFieldTrialEnabled()) {
+    if (selected_send_codec->flexfec_payload_type != -1) {
+      LOG(LS_INFO) << "Remote supports flexfec-03, but we will not send since "
+                   << "WebRTC-FlexFEC-03 field trial is not enabled.";
+    }
+    selected_send_codec->flexfec_payload_type = -1;
+  }
+
   if (!send_codec_ || *selected_send_codec != *send_codec_)
     changed_params->codec = selected_send_codec;
 
   // Handle RTP header extensions.
   std::vector<webrtc::RtpExtension> filtered_extensions = FilterRtpExtensions(
       params.extensions, webrtc::RtpExtension::IsSupportedForVideo, true);
   if (!send_rtp_extensions_ || (*send_rtp_extensions_ != filtered_extensions)) {
     changed_params->rtp_header_extensions =
         rtc::Optional<std::vector<webrtc::RtpExtension>>(filtered_extensions);
   }
@@ skipping 537 matching lines @@
 
   config->rtp.remb = send_codec_ ? HasRemb(send_codec_->codec) : false;
   config->rtp.transport_cc =
       send_codec_ ? HasTransportCc(send_codec_->codec) : false;
 
   sp.GetFidSsrc(ssrc, &config->rtp.rtx_ssrc);
 
   config->rtp.extensions = recv_rtp_extensions_;
 
   // TODO(brandtr): Generalize when we add support for multistream protection.
-  if (sp.GetFecFrSsrc(ssrc, &flexfec_config->remote_ssrc)) {
+  if (IsFlexfecAdvertisedFieldTrialEnabled() &&
+      sp.GetFecFrSsrc(ssrc, &flexfec_config->remote_ssrc)) {
     flexfec_config->protected_media_ssrcs = {ssrc};
     flexfec_config->local_ssrc = config->rtp.local_ssrc;
     flexfec_config->rtcp_mode = config->rtp.rtcp_mode;
     // TODO(brandtr): We should be spec-compliant and set |transport_cc| here
     // based on the rtcp-fb for the FlexFEC codec, not the media codec.
     flexfec_config->transport_cc = config->rtp.transport_cc;
     flexfec_config->rtp_header_extensions = config->rtp.extensions;
   }
 }
 
@@ skipping 315 matching lines @@
 
   // FlexFEC SSRCs.
   // TODO(brandtr): This code needs to be generalized when we add support for
   // multistream protection.
   if (IsFlexfecFieldTrialEnabled()) {
     uint32_t flexfec_ssrc;
     bool flexfec_enabled = false;
     for (uint32_t primary_ssrc : parameters_.config.rtp.ssrcs) {
       if (sp.GetFecFrSsrc(primary_ssrc, &flexfec_ssrc)) {
         if (flexfec_enabled) {
-          LOG(LS_INFO) << "Multiple FlexFEC streams proposed by remote, but "
+          LOG(LS_INFO) << "Multiple FlexFEC streams in local SDP, but "
                           "our implementation only supports a single FlexFEC "
                           "stream. Will not enable FlexFEC for proposed "
                           "stream with SSRC: "
                        << flexfec_ssrc << ".";
           continue;
         }
 
         flexfec_enabled = true;
         parameters_.config.rtp.flexfec.ssrc = flexfec_ssrc;
         parameters_.config.rtp.flexfec.protected_media_ssrcs = {primary_ssrc};
@@ skipping 154 matching lines @@
   if (new_encoder.external) {
     webrtc::VideoCodecType type =
         webrtc::PayloadNameToCodecType(codec_settings.codec.name)
             .value_or(webrtc::kVideoCodecUnknown);
     parameters_.config.encoder_settings.internal_source =
         external_encoder_factory_->EncoderTypeHasInternalSource(type);
   } else {
     parameters_.config.encoder_settings.internal_source = false;
   }
   parameters_.config.rtp.ulpfec = codec_settings.ulpfec;
-  if (IsFlexfecFieldTrialEnabled()) {
-    parameters_.config.rtp.flexfec.payload_type =
-        codec_settings.flexfec_payload_type;
-  }
+  parameters_.config.rtp.flexfec.payload_type =
+      codec_settings.flexfec_payload_type;
 
   // Set RTX payload type if RTX is enabled.
   if (!parameters_.config.rtp.rtx.ssrcs.empty()) {
     if (codec_settings.rtx_payload_type == -1) {
       LOG(LS_WARNING) << "RTX SSRCs configured but there's no configured RTX "
                          "payload type. Ignoring.";
       parameters_.config.rtp.rtx.ssrcs.clear();
     } else {
       parameters_.config.rtp.rtx.payload_type = codec_settings.rtx_payload_type;
     }
@@ skipping 797 matching lines @@
         rtx_mapping[video_codecs[i].codec.id] !=
             ulpfec_config.red_payload_type) {
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket