Add experimental simulcast screen content mode

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 283 matching lines @@
         max_qp_(max_qp),
         max_framerate_(max_framerate),
         is_screencast_(is_screencast),
         conference_mode_(conference_mode) {}
 
  private:
   std::vector<webrtc::VideoStream> CreateEncoderStreams(
       int width,
       int height,
       const webrtc::VideoEncoderConfig& encoder_config) override {
-    RTC_DCHECK(encoder_config.number_of_streams > 1 ? !is_screencast_ : true);
-    if (encoder_config.number_of_streams > 1) {
+    if (is_screencast_ &&
+        (!conference_mode_ || !cricket::UseSimulcastScreenshare())) {
+      RTC_DCHECK_EQ(1, encoder_config.number_of_streams);
+    }
+    if (encoder_config.number_of_streams > 1 ||
+        (CodecNamesEq(codec_name_, kVp8CodecName) && is_screencast_ &&
+         conference_mode_)) {
       return GetSimulcastConfig(encoder_config.number_of_streams, width, height,
                                 encoder_config.max_bitrate_bps, max_qp_,
-                                max_framerate_);
+                                max_framerate_, is_screencast_);
     }
 
     // For unset max bitrates set default bitrate for non-simulcast.
     int max_bitrate_bps =
         (encoder_config.max_bitrate_bps > 0)
             ? encoder_config.max_bitrate_bps
             : GetMaxDefaultVideoBitrateKbps(width, height) * 1000;
 
     webrtc::VideoStream stream;
     stream.width = width;
     stream.height = height;
     stream.max_framerate = max_framerate_;
     stream.min_bitrate_bps = kMinVideoBitrateKbps * 1000;
     stream.target_bitrate_bps = stream.max_bitrate_bps = max_bitrate_bps;
     stream.max_qp = max_qp_;
 
-    // Conference mode screencast uses 2 temporal layers split at 100kbit.
-    if (conference_mode_ && is_screencast_) {
-      ScreenshareLayerConfig config = ScreenshareLayerConfig::GetDefault();
-      // For screenshare in conference mode, tl0 and tl1 bitrates are
-      // piggybacked
-      // on the VideoCodec struct as target and max bitrates, respectively.
-      // See eg. webrtc::VP8EncoderImpl::SetRates().
-      stream.target_bitrate_bps = config.tl0_bitrate_kbps * 1000;
-      stream.max_bitrate_bps = config.tl1_bitrate_kbps * 1000;
-      stream.temporal_layer_thresholds_bps.clear();
-      stream.temporal_layer_thresholds_bps.push_back(config.tl0_bitrate_kbps *
-                                                     1000);
-    }
-
     if (CodecNamesEq(codec_name_, kVp9CodecName) && !is_screencast_) {
       stream.temporal_layer_thresholds_bps.resize(
           GetDefaultVp9TemporalLayers() - 1);
     }
 
     std::vector<webrtc::VideoStream> streams;
     streams.push_back(stream);
     return streams;
   }
 
@@ skipping 1195 matching lines @@
     // TODO(deadbeef): Don't duplicate information between send_params,
     // rtp_extensions, options, etc.
     const VideoSendParameters& send_params)
     : 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),
       parameters_(std::move(config), options, max_bitrate_bps, codec_settings),
       rtp_parameters_(CreateRtpParametersWithOneEncoding()),
       allocated_encoder_(nullptr, cricket::VideoCodec(), false),
       sending_(false) {
   parameters_.config.rtp.max_packet_size = kVideoMtu;
   parameters_.conference_mode = send_params.conference_mode;
 
   sp.GetPrimarySsrcs(&parameters_.config.rtp.ssrcs);
@@ skipping 107 matching lines @@
   // Try creating external encoder.
   if (external_encoder_factory_ != nullptr &&
       FindMatchingCodec(external_encoder_factory_->supported_codecs(), codec)) {
     webrtc::VideoEncoder* encoder =
         external_encoder_factory_->CreateVideoEncoder(codec);
     if (encoder != nullptr)
       return AllocatedEncoder(encoder, codec, true /* is_external */);
   }
 
   // Try creating internal encoder.
-  InternalEncoderFactory internal_encoder_factory;
-  if (FindMatchingCodec(internal_encoder_factory.supported_codecs(), codec)) {
-    return AllocatedEncoder(internal_encoder_factory.CreateVideoEncoder(codec),
-                            codec, false /* is_external */);
+  if (FindMatchingCodec(internal_encoder_factory_->supported_codecs(), codec)) {
+    if (parameters_.encoder_config.content_type ==
+            webrtc::VideoEncoderConfig::ContentType::kScreen &&
+        parameters_.conference_mode && UseSimulcastScreenshare()) {
+      // TODO(sprang): Remove this adapter once libvpx supports simulcast with
+      // same-resolution substreams.
+      WebRtcSimulcastEncoderFactory adapter_factory(
+          internal_encoder_factory_.get());
+      return AllocatedEncoder(adapter_factory.CreateVideoEncoder(codec), codec,
+                              false /* is_external */);
+    }
+    return AllocatedEncoder(
+        internal_encoder_factory_->CreateVideoEncoder(codec), codec,
+        false /* is_external */);
   }
 
   // This shouldn't happen, we should not be trying to create something we don't
   // support.
   RTC_NOTREACHED();
   return AllocatedEncoder(NULL, cricket::VideoCodec(), false);
 }
 
 void WebRtcVideoChannel2::WebRtcVideoSendStream::DestroyVideoEncoder(
     AllocatedEncoder* encoder) {
@@ skipping 156 matching lines @@
     encoder_config.content_type =
         webrtc::VideoEncoderConfig::ContentType::kScreen;
   } else {
     encoder_config.min_transmit_bitrate_bps = 0;
     encoder_config.content_type =
         webrtc::VideoEncoderConfig::ContentType::kRealtimeVideo;
   }
 
   // By default, the stream count for the codec configuration should match the
   // number of negotiated ssrcs. But if the codec is blacklisted for simulcast
-  // or a screencast, only configure a single stream.
+  // or a screencast (and not in simulcast screenshare experiment), only
+  // configure a single stream.
   encoder_config.number_of_streams = parameters_.config.rtp.ssrcs.size();
-  if (IsCodecBlacklistedForSimulcast(codec.name) || is_screencast) {
+  if (IsCodecBlacklistedForSimulcast(codec.name) ||
+      (is_screencast && !UseSimulcastScreenshare())) {
     encoder_config.number_of_streams = 1;
   }
 
   int stream_max_bitrate =
       MinPositive(rtp_parameters_.encodings[0].max_bitrate_bps,
                   parameters_.max_bitrate_bps);
 
   int codec_max_bitrate_kbps;
   if (codec.GetParam(kCodecParamMaxBitrate, &codec_max_bitrate_kbps)) {
     stream_max_bitrate = codec_max_bitrate_kbps * 1000;
@@ skipping 636 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