Reland of Add experimental simulcast screen content mode

webrtc/modules/video_coding/video_codec_initializer.cc

 /*
  *  Copyright (c) 2016 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 20 matching lines @@
     std::unique_ptr<VideoBitrateAllocator>* bitrate_allocator) {
   *codec =
       VideoEncoderConfigToVideoCodec(config, streams, settings.payload_name,
                                      settings.payload_type, nack_enabled);
 
   std::unique_ptr<TemporalLayersFactory> tl_factory;
   switch (codec->codecType) {
     case kVideoCodecVP8: {
       if (!codec->VP8()->tl_factory) {
         if (codec->mode == kScreensharing &&
-            codec->numberOfSimulcastStreams == 1 &&
-            codec->VP8()->numberOfTemporalLayers == 2) {
+            (codec->numberOfSimulcastStreams > 1 ||
+             (codec->numberOfSimulcastStreams == 1 &&
+              codec->VP8()->numberOfTemporalLayers == 2))) {
           // Conference mode temporal layering for screen content.
           tl_factory.reset(new ScreenshareTemporalLayersFactory());
         } else {
           // Standard video temporal layers.
           tl_factory.reset(new TemporalLayersFactory());
         }
         codec->VP8()->tl_factory = tl_factory.get();
       }
       break;
     }
@@ skipping 42 matching lines @@
   memset(&video_codec, 0, sizeof(video_codec));
   video_codec.codecType = PayloadNameToCodecType(payload_name)
                               .value_or(VideoCodecType::kVideoCodecGeneric);
 
   switch (config.content_type) {
     case VideoEncoderConfig::ContentType::kRealtimeVideo:
       video_codec.mode = kRealtimeVideo;
       break;
     case VideoEncoderConfig::ContentType::kScreen:
       video_codec.mode = kScreensharing;
-      if (streams.size() == 1 &&
+      if (streams.size() >= 1 &&
           streams[0].temporal_layer_thresholds_bps.size() == 1) {
         video_codec.targetBitrate =
             streams[0].temporal_layer_thresholds_bps[0] / 1000;
       }
       break;
   }
 
   if (config.encoder_specific_settings)
     config.encoder_specific_settings->FillEncoderSpecificSettings(&video_codec);
 
@@ skipping 57 matching lines @@
     RTC_DCHECK_LE(video_codec.VP9()->numberOfSpatialLayers,
                   kMaxSimulcastStreams);
     for (size_t i = 0; i < config.spatial_layers.size(); ++i)
       video_codec.spatialLayers[i] = config.spatial_layers[i];
   }
   for (size_t i = 0; i < streams.size(); ++i) {
     SimulcastStream* sim_stream = &video_codec.simulcastStream[i];
     RTC_DCHECK_GT(streams[i].width, 0);
     RTC_DCHECK_GT(streams[i].height, 0);
     RTC_DCHECK_GT(streams[i].max_framerate, 0);
-    // Different framerates not supported per stream at the moment.
-    RTC_DCHECK_EQ(streams[i].max_framerate, streams[0].max_framerate);
+    // Different framerates not supported per stream at the moment, unless it's
+    // screenshare where there is an exception and a simulcast encoder adapter,
+    // which supports different framerates, is used instead.
+    if (config.content_type != VideoEncoderConfig::ContentType::kScreen) {
+      RTC_DCHECK_EQ(streams[i].max_framerate, streams[0].max_framerate);
+    }
     RTC_DCHECK_GE(streams[i].min_bitrate_bps, 0);
     RTC_DCHECK_GE(streams[i].target_bitrate_bps, streams[i].min_bitrate_bps);
     RTC_DCHECK_GE(streams[i].max_bitrate_bps, streams[i].target_bitrate_bps);
     RTC_DCHECK_GE(streams[i].max_qp, 0);
 
     sim_stream->width = static_cast<uint16_t>(streams[i].width);
     sim_stream->height = static_cast<uint16_t>(streams[i].height);
     sim_stream->minBitrate = streams[i].min_bitrate_bps / 1000;
     sim_stream->targetBitrate = streams[i].target_bitrate_bps / 1000;
     sim_stream->maxBitrate = streams[i].max_bitrate_bps / 1000;
@@ skipping 21 matching lines @@
   }
   if (video_codec.maxBitrate < kEncoderMinBitrateKbps)
     video_codec.maxBitrate = kEncoderMinBitrateKbps;
 
   RTC_DCHECK_GT(streams[0].max_framerate, 0);
   video_codec.maxFramerate = streams[0].max_framerate;
   return video_codec;
 }
 
 }  // namespace webrtc