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 572 matching lines @@
     const VideoOptions& options,
     WebRtcVideoEncoderFactory* external_encoder_factory,
     WebRtcVideoDecoderFactory* external_decoder_factory)
     : VideoMediaChannel(config),
       call_(call),
       unsignalled_ssrc_handler_(&default_unsignalled_ssrc_handler_),
       video_config_(config.video),
       external_encoder_factory_(external_encoder_factory),
       external_decoder_factory_(external_decoder_factory),
       default_send_options_(options),
-      last_stats_log_ms_(-1) {
+      last_stats_log_ms_(-1),
+      map_flexfec_recv_(IsFlexfecAdvertisedFieldTrialEnabled()),
+      map_flexfec_send_(IsFlexfecFieldTrialEnabled()) {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
 
   rtcp_receiver_report_ssrc_ = kDefaultRtcpReceiverReportSsrc;
   sending_ = false;
-  recv_codecs_ = MapCodecs(GetSupportedCodecs(external_encoder_factory));
+  recv_codecs_ = MapCodecs(GetSupportedCodecs(external_encoder_factory),
+                           map_flexfec_recv_);
 }
 
 WebRtcVideoChannel2::~WebRtcVideoChannel2() {
   for (auto& kv : send_streams_)
     delete kv.second;
   for (auto& kv : receive_streams_)
     delete kv.second;
 }
 
 rtc::Optional<WebRtcVideoChannel2::VideoCodecSettings>
@@ skipping 41 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 =
-      SelectSendVideoCodec(MapCodecs(params.codecs));
+      SelectSendVideoCodec(MapCodecs(params.codecs, map_flexfec_send_));
 
   if (!selected_send_codec) {
     LOG(LS_ERROR) << "No video codecs supported.";
     return false;
   }
 
   if (!send_codec_ || *selected_send_codec != *send_codec_)
     changed_params->codec = selected_send_codec;
 
   // Handle RTP header extensions.
@@ skipping 220 matching lines @@
 bool WebRtcVideoChannel2::GetChangedRecvParameters(
     const VideoRecvParameters& params,
     ChangedRecvParameters* changed_params) const {
   if (!ValidateCodecFormats(params.codecs) ||
       !ValidateRtpExtensions(params.extensions)) {
     return false;
   }
 
   // Handle receive codecs.
   const std::vector<VideoCodecSettings> mapped_codecs =
-      MapCodecs(params.codecs);
+      MapCodecs(params.codecs, map_flexfec_recv_);
   if (mapped_codecs.empty()) {
     LOG(LS_ERROR) << "SetRecvParameters called without any video codecs.";
     return false;
   }
 
   // Verify that every mapped codec is supported locally.
   const std::vector<VideoCodec> local_supported_codecs =
       GetSupportedCodecs(external_encoder_factory_);
   for (const VideoCodecSettings& mapped_codec : mapped_codecs) {
     if (!FindMatchingCodec(local_supported_codecs, mapped_codec.codec)) {
@@ skipping 149 matching lines @@
     send_ssrcs_.insert(used_ssrc);
 
   webrtc::VideoSendStream::Config config(this);
   config.suspend_below_min_bitrate = video_config_.suspend_below_min_bitrate;
   config.periodic_alr_bandwidth_probing =
       video_config_.periodic_alr_bandwidth_probing;
   WebRtcVideoSendStream* stream = new WebRtcVideoSendStream(
       call_, sp, std::move(config), default_send_options_,
       external_encoder_factory_, video_config_.enable_cpu_overuse_detection,
       bitrate_config_.max_bitrate_bps, send_codec_, send_rtp_extensions_,
-      send_params_);
+      send_params_, map_flexfec_send_);
 
   uint32_t ssrc = sp.first_ssrc();
   RTC_DCHECK(ssrc != 0);
   send_streams_[ssrc] = stream;
 
   if (rtcp_receiver_report_ssrc_ == kDefaultRtcpReceiverReportSsrc) {
     rtcp_receiver_report_ssrc_ = ssrc;
     LOG(LS_INFO) << "SetLocalSsrc on all the receive streams because we added "
                     "a send stream.";
     for (auto& kv : receive_streams_)
@@ skipping 132 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 (map_flexfec_recv_ &&
+      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 277 matching lines @@
     const StreamParams& sp,
     webrtc::VideoSendStream::Config config,
     const VideoOptions& options,
     WebRtcVideoEncoderFactory* external_encoder_factory,
     bool enable_cpu_overuse_detection,
     int max_bitrate_bps,
     const rtc::Optional<VideoCodecSettings>& codec_settings,
     const rtc::Optional<std::vector<webrtc::RtpExtension>>& rtp_extensions,
     // TODO(deadbeef): Don't duplicate information between send_params,
     // rtp_extensions, options, etc.
-    const VideoSendParameters& send_params)
+    const VideoSendParameters& send_params,
+    bool map_flexfec_send)
     : worker_thread_(rtc::Thread::Current()),
       ssrcs_(sp.ssrcs),
       ssrc_groups_(sp.ssrc_groups),
       call_(call),
       enable_cpu_overuse_detection_(enable_cpu_overuse_detection),
       source_(nullptr),
       external_encoder_factory_(external_encoder_factory),
       internal_encoder_factory_(new InternalEncoderFactory()),
       stream_(nullptr),
       encoder_sink_(nullptr),
@@ skipping 11 matching lines @@
   rtp_parameters_.encodings[0].ssrc =
       rtc::Optional<uint32_t>(parameters_.config.rtp.ssrcs[0]);
 
   // RTX.
   sp.GetFidSsrcs(parameters_.config.rtp.ssrcs,
                  &parameters_.config.rtp.rtx.ssrcs);
 
   // FlexFEC SSRCs.
   // TODO(brandtr): This code needs to be generalized when we add support for
   // multistream protection.
-  if (IsFlexfecFieldTrialEnabled()) {
+  if (map_flexfec_send) {

[perkj_webrtc, 2017/05/12 12:05:05]

rename variable or keep function call. is_flexfec_field_trial_.

[brandtr, 2017/05/15 12:24:13]

Kept function call.

     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 693 matching lines @@
          flexfec_payload_type == other.flexfec_payload_type &&
          rtx_payload_type == other.rtx_payload_type;
 }
 
 bool WebRtcVideoChannel2::VideoCodecSettings::operator!=(
     const WebRtcVideoChannel2::VideoCodecSettings& other) const {
   return !(*this == other);
 }
 
 std::vector<WebRtcVideoChannel2::VideoCodecSettings>
-WebRtcVideoChannel2::MapCodecs(const std::vector<VideoCodec>& codecs) {
+WebRtcVideoChannel2::MapCodecs(const std::vector<VideoCodec>& codecs,
+                               bool map_flexfec) {

[perkj_webrtc, 2017/05/12 12:05:05]

remove and use IsFlexfecFieldTrialEnabled() in here instead.

[brandtr, 2017/05/15 12:24:13]

Done.

As was clear from our F2F discussion, however, this optimization is only helpful
for the sender side. So I moved the logic to GetChangedSendParameters instead.
This makes it easier to understand.

   RTC_DCHECK(!codecs.empty());
 
   std::vector<VideoCodecSettings> video_codecs;
   std::map<int, bool> payload_used;
   std::map<int, VideoCodec::CodecType> payload_codec_type;
   // |rtx_mapping| maps video payload type to rtx payload type.
   std::map<int, int> rtx_mapping;
 
   webrtc::UlpfecConfig ulpfec_config;
   int flexfec_payload_type = -1;
@@ skipping 71 matching lines @@
       return std::vector<VideoCodecSettings>();
     }
 
     if (it->first == ulpfec_config.red_payload_type) {
       ulpfec_config.red_rtx_payload_type = it->second;
     }
   }
 
   for (size_t i = 0; i < video_codecs.size(); ++i) {
     video_codecs[i].ulpfec = ulpfec_config;
-    video_codecs[i].flexfec_payload_type = flexfec_payload_type;
+    // Only map the FlexFEC payload type if we know that FlexFEC will actually
+    // be used. By doing that, we reduce the number of
+    // VideoReceiveStream/VideoSendStream object recreations during SDP
+    // renegotiation.
+    if (map_flexfec) {
+      video_codecs[i].flexfec_payload_type = flexfec_payload_type;
+    }
     if (rtx_mapping[video_codecs[i].codec.id] != 0 &&
         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