Reland "Only enable conference mode simulcast allocations with flag enabled"

This is a reland of 32ca95145c4636374266f5b5d4d1ac43658bc758

Fix includes not enabling the screenshare conference behavior on non
screenshare sources even if the flag is enabled.

Original change's description:
> Only enable conference mode simulcast allocations with flag enabled
>
> Non-conference mode simulcast screenshares were mistakenly using the
> conference mode semantics in the simulcast rate allocator, which broke
> spec compliant usage in some situation.
>
> This behavior should only be used when explicitly using the SDP entry
> "a=x-google-flag:conference" in both offer and answer.
>
> Bug: webrtc:11310, chromium:1093819
> Change-Id: Ibcba75c88a8405d60467546b33977a782e04e469
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/179081
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
> Commit-Queue: Florent Castelli <orphis@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31828}

Bug: webrtc:11310
Bug: chromium:1093819
Change-Id: Ic933f93a5c4bad20583354fe821f8a1170e911cd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180802
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31847}

api/video/video_bitrate_allocator.cc

@@ -49,4 +49,6 @@ VideoBitrateAllocation VideoBitrateAllocator::Allocate(
   return GetAllocation(parameters.total_bitrate.bps(), parameters.framerate);
 }
 
+void VideoBitrateAllocator::SetLegacyConferenceMode(bool enabled) {}
+
 }  // namespace webrtc

api/video/video_bitrate_allocator.h

@@ -40,6 +40,10 @@ class VideoBitrateAllocator {
 
   virtual VideoBitrateAllocation Allocate(
       VideoBitrateAllocationParameters parameters);
+
+  // Deprecated: Only used to work around issues with the legacy conference
+  // screenshare mode and shouldn't be needed by any subclasses.
+  virtual void SetLegacyConferenceMode(bool enabled);
 };
 
 class VideoBitrateAllocationObserver {

api/video_codecs/video_codec.cc

@@ -83,6 +83,7 @@ VideoCodec::VideoCodec()
       mode(VideoCodecMode::kRealtimeVideo),
       expect_encode_from_texture(false),
       timing_frame_thresholds({0, 0}),
+      legacy_conference_mode(false),
       codec_specific_() {}
 
 VideoCodecVP8* VideoCodec::VP8() {

api/video_codecs/video_codec.h

@@ -146,6 +146,9 @@ class RTC_EXPORT VideoCodec {
     uint16_t outlier_ratio_percent;
   } timing_frame_thresholds;
 
+  // Legacy Google conference mode flag for simulcast screenshare
+  bool legacy_conference_mode;
+
   bool operator==(const VideoCodec& other) const = delete;
   bool operator!=(const VideoCodec& other) const = delete;
 

api/video_codecs/video_encoder_config.cc

@@ -55,7 +55,8 @@ VideoEncoderConfig::VideoEncoderConfig()
       min_transmit_bitrate_bps(0),
       max_bitrate_bps(0),
       bitrate_priority(1.0),
-      number_of_streams(0) {}
+      number_of_streams(0),
+      legacy_conference_mode(false) {}
 
 VideoEncoderConfig::VideoEncoderConfig(VideoEncoderConfig&&) = default;
 

api/video_codecs/video_encoder_config.h

@@ -176,6 +176,9 @@ class VideoEncoderConfig {
   // Max number of encoded VideoStreams to produce.
   size_t number_of_streams;
 
+  // Legacy Google conference mode flag for simulcast screenshare
+  bool legacy_conference_mode;
+
  private:
   // Access to the copy constructor is private to force use of the Copy()
   // method for those exceptional cases where we do use it.

media/engine/simulcast_encoder_adapter.cc

@@ -619,6 +619,10 @@ void SimulcastEncoderAdapter::PopulateStreamCodec(
   // TODO(ronghuawu): what to do with targetBitrate.
 
   stream_codec->startBitrate = start_bitrate_kbps;
+
+  // Legacy screenshare mode is only enabled for the first simulcast layer
+  stream_codec->legacy_conference_mode =
+      inst.legacy_conference_mode && stream_index == 0;
 }
 
 bool SimulcastEncoderAdapter::Initialized() const {

media/engine/webrtc_video_engine.cc

@@ -2399,6 +2399,8 @@ WebRtcVideoChannel::WebRtcVideoSendStream::CreateVideoEncoderConfig(
     }
   }
 
+  encoder_config.legacy_conference_mode = parameters_.conference_mode;
+
   int max_qp = kDefaultQpMax;
   codec.GetParam(kCodecParamMaxQuantization, &max_qp);
   encoder_config.video_stream_factory =
@@ -3394,7 +3396,7 @@ std::vector<webrtc::VideoStream> EncoderStreamFactory::CreateEncoderStreams(
       ((absl::EqualsIgnoreCase(codec_name_, kVp8CodecName) ||
         absl::EqualsIgnoreCase(codec_name_, kH264CodecName)) &&
        is_screenshare_ && conference_mode_)) {
-    return CreateSimulcastOrConfereceModeScreenshareStreams(
+    return CreateSimulcastOrConferenceModeScreenshareStreams(
         width, height, encoder_config, experimental_min_bitrate);
   }
 
@@ -3483,7 +3485,7 @@ EncoderStreamFactory::CreateDefaultVideoStreams(
 }
 
 std::vector<webrtc::VideoStream>
-EncoderStreamFactory::CreateSimulcastOrConfereceModeScreenshareStreams(
+EncoderStreamFactory::CreateSimulcastOrConferenceModeScreenshareStreams(
     int width,
     int height,
     const webrtc::VideoEncoderConfig& encoder_config,

media/engine/webrtc_video_engine.h

@@ -661,7 +661,7 @@ class EncoderStreamFactory
       const absl::optional<webrtc::DataRate>& experimental_min_bitrate) const;
 
   std::vector<webrtc::VideoStream>
-  CreateSimulcastOrConfereceModeScreenshareStreams(
+  CreateSimulcastOrConferenceModeScreenshareStreams(
       int width,
       int height,
       const webrtc::VideoEncoderConfig& encoder_config,

modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc

@@ -879,7 +879,7 @@ size_t LibvpxVp8Encoder::SteadyStateSize(int sid, int tid) {
   const int encoder_id = encoders_.size() - 1 - sid;
   size_t bitrate_bps;
   float fps;
-  if (SimulcastUtility::IsConferenceModeScreenshare(codec_) ||
+  if ((SimulcastUtility::IsConferenceModeScreenshare(codec_) && sid == 0) ||
       vpx_configs_[encoder_id].ts_number_layers <= 1) {
     // In conference screenshare there's no defined per temporal layer bitrate
     // and framerate.

modules/video_coding/codecs/vp8/test/vp8_impl_unittest.cc

@@ -523,6 +523,7 @@ TEST_F(TestVp8Impl, KeepsTimestampOnReencode) {
   codec_settings_.maxBitrate = 1000;
   codec_settings_.mode = VideoCodecMode::kScreensharing;
   codec_settings_.VP8()->numberOfTemporalLayers = 2;
+  codec_settings_.legacy_conference_mode = true;
 
   EXPECT_CALL(*vpx, img_wrap(_, _, _, _, _, _))
       .WillOnce(Invoke([](vpx_image_t* img, vpx_img_fmt_t fmt, unsigned int d_w,
@@ -653,6 +654,7 @@ TEST_F(TestVp8Impl, GetEncoderInfoFpsAllocationScreenshareLayers) {
   codec_settings_.simulcastStream[0].maxBitrate =
       kLegacyScreenshareTl1BitrateKbps;
   codec_settings_.simulcastStream[0].numberOfTemporalLayers = 2;
+  codec_settings_.legacy_conference_mode = true;
   EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
             encoder_->InitEncode(&codec_settings_, kSettings));
 

modules/video_coding/utility/simulcast_rate_allocator.cc

@@ -61,7 +61,8 @@ float SimulcastRateAllocator::GetTemporalRateAllocation(
 SimulcastRateAllocator::SimulcastRateAllocator(const VideoCodec& codec)
     : codec_(codec),
       stable_rate_settings_(StableTargetRateExperiment::ParseFromFieldTrials()),
-      rate_control_settings_(RateControlSettings::ParseFromFieldTrials()) {}
+      rate_control_settings_(RateControlSettings::ParseFromFieldTrials()),
+      legacy_conference_mode_(false) {}
 
 SimulcastRateAllocator::~SimulcastRateAllocator() = default;
 
@@ -228,12 +229,7 @@ void SimulcastRateAllocator::DistributeAllocationToTemporalLayers(
     uint32_t max_bitrate_kbps;
     // Legacy temporal-layered only screenshare, or simulcast screenshare
     // with legacy mode for simulcast stream 0.
-    const bool conference_screenshare_mode =
-        codec_.mode == VideoCodecMode::kScreensharing &&
-        ((num_spatial_streams == 1 && num_temporal_streams == 2) ||  // Legacy.
-         (num_spatial_streams > 1 && simulcast_id == 0 &&
-          num_temporal_streams == 2));  // Simulcast.
-    if (conference_screenshare_mode) {
+    if (legacy_conference_mode_ && simulcast_id == 0) {
       // TODO(holmer): This is a "temporary" hack for screensharing, where we
       // interpret the startBitrate as the encoder target bitrate. This is
       // to allow for a different max bitrate, so if the codec can't meet
@@ -253,7 +249,7 @@ void SimulcastRateAllocator::DistributeAllocationToTemporalLayers(
     if (num_temporal_streams == 1) {
       tl_allocation.push_back(target_bitrate_kbps);
     } else {
-      if (conference_screenshare_mode) {
+      if (legacy_conference_mode_ && simulcast_id == 0) {
         tl_allocation = ScreenshareTemporalLayerAllocation(
             target_bitrate_kbps, max_bitrate_kbps, simulcast_id);
       } else {
@@ -338,4 +334,8 @@ int SimulcastRateAllocator::NumTemporalStreams(size_t simulcast_id) const {
           : codec_.simulcastStream[simulcast_id].numberOfTemporalLayers);
 }
 
+void SimulcastRateAllocator::SetLegacyConferenceMode(bool enabled) {
+  legacy_conference_mode_ = enabled;
+}
+
 }  // namespace webrtc

modules/video_coding/utility/simulcast_rate_allocator.h

@@ -38,6 +38,8 @@ class SimulcastRateAllocator : public VideoBitrateAllocator {
                                          int temporal_id,
                                          bool base_heavy_tl3_alloc);
 
+  void SetLegacyConferenceMode(bool mode) override;
+
  private:
   void DistributeAllocationToSimulcastLayers(
       DataRate total_bitrate,
@@ -58,6 +60,7 @@ class SimulcastRateAllocator : public VideoBitrateAllocator {
   const StableTargetRateExperiment stable_rate_settings_;
   const RateControlSettings rate_control_settings_;
   std::vector<bool> stream_enabled_;
+  bool legacy_conference_mode_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(SimulcastRateAllocator);
 };

modules/video_coding/utility/simulcast_rate_allocator_unittest.cc

@@ -88,8 +88,9 @@ class SimulcastRateAllocatorTest : public ::testing::TestWithParam<bool> {
     EXPECT_EQ(sum, actual.get_sum_bps());
   }
 
-  void CreateAllocator() {
+  void CreateAllocator(bool legacy_conference_mode = false) {
     allocator_.reset(new SimulcastRateAllocator(codec_));
+    allocator_->SetLegacyConferenceMode(legacy_conference_mode);
   }
 
   void SetupCodec3SL3TL(const std::vector<bool>& active_streams) {
@@ -669,9 +670,9 @@ INSTANTIATE_TEST_SUITE_P(ScreenshareTest,
                          ScreenshareRateAllocationTest,
                          ::testing::Bool());
 
-TEST_P(ScreenshareRateAllocationTest, BitrateBelowTl0) {
+TEST_P(ScreenshareRateAllocationTest, ConferenceBitrateBelowTl0) {
   SetupConferenceScreenshare(GetParam());
-  CreateAllocator();
+  CreateAllocator(true);
 
   VideoBitrateAllocation allocation =
       allocator_->Allocate(VideoBitrateAllocationParameters(
@@ -684,9 +685,9 @@ TEST_P(ScreenshareRateAllocationTest, BitrateBelowTl0) {
   EXPECT_EQ(allocation.is_bw_limited(), GetParam());
 }
 
-TEST_P(ScreenshareRateAllocationTest, BitrateAboveTl0) {
+TEST_P(ScreenshareRateAllocationTest, ConferenceBitrateAboveTl0) {
   SetupConferenceScreenshare(GetParam());
-  CreateAllocator();
+  CreateAllocator(true);
 
   uint32_t target_bitrate_kbps =
       (kLegacyScreenshareTargetBitrateKbps + kLegacyScreenshareMaxBitrateKbps) /
@@ -704,10 +705,10 @@ TEST_P(ScreenshareRateAllocationTest, BitrateAboveTl0) {
   EXPECT_EQ(allocation.is_bw_limited(), GetParam());
 }
 
-TEST_F(ScreenshareRateAllocationTest, BitrateAboveTl1) {
+TEST_F(ScreenshareRateAllocationTest, ConferenceBitrateAboveTl1) {
   // This test is only for the non-simulcast case.
   SetupConferenceScreenshare(false);
-  CreateAllocator();
+  CreateAllocator(true);
 
   VideoBitrateAllocation allocation =
       allocator_->Allocate(VideoBitrateAllocationParameters(

modules/video_coding/utility/simulcast_utility.cc

@@ -84,16 +84,8 @@ bool SimulcastUtility::ValidSimulcastParameters(const VideoCodec& codec,
 }
 
 bool SimulcastUtility::IsConferenceModeScreenshare(const VideoCodec& codec) {
-  if (codec.mode != VideoCodecMode::kScreensharing ||
-      NumberOfTemporalLayers(codec, 0) != 2) {
-    return false;
-  }
-
-  // Fixed default bitrates for legacy screenshare layers mode.
-  return (codec.numberOfSimulcastStreams == 0 && codec.maxBitrate == 1000) ||
-         (codec.numberOfSimulcastStreams >= 1 &&
-          codec.simulcastStream[0].maxBitrate == 1000 &&
-          codec.simulcastStream[0].targetBitrate == 200);
+  return codec.mode == VideoCodecMode::kScreensharing &&
+         codec.legacy_conference_mode;
 }
 
 int SimulcastUtility::NumberOfTemporalLayers(const VideoCodec& codec,

modules/video_coding/video_codec_initializer.cc

@@ -68,6 +68,10 @@ VideoCodec VideoCodecInitializer::VideoEncoderConfigToVideoCodec(
       break;
   }
 
+  video_codec.legacy_conference_mode =
+      config.content_type == VideoEncoderConfig::ContentType::kScreen &&
+      config.legacy_conference_mode;
+
   // TODO(nisse): The plType field should be deleted. Luckily, our
   // callers don't need it.
   video_codec.plType = 0;

modules/video_coding/video_codec_initializer_unittest.cc

@@ -42,7 +42,8 @@ static const uint32_t kDefaultTargetBitrateBps = 2000000;
 static const uint32_t kDefaultMaxBitrateBps = 2000000;
 static const uint32_t kDefaultMinTransmitBitrateBps = 400000;
 static const int kDefaultMaxQp = 48;
-static const uint32_t kScreenshareTl0BitrateBps = 200000;
+static const uint32_t kScreenshareTl0BitrateBps = 120000;
+static const uint32_t kScreenshareConferenceTl0BitrateBps = 200000;
 static const uint32_t kScreenshareCodecTargetBitrateBps = 200000;
 static const uint32_t kScreenshareDefaultFramerate = 5;
 // Bitrates for the temporal layers of the higher screenshare simulcast stream.
@@ -126,7 +127,7 @@ class VideoCodecInitializerTest : public ::testing::Test {
   VideoStream DefaultScreenshareStream() {
     VideoStream stream = DefaultStream();
     stream.min_bitrate_bps = 30000;
-    stream.target_bitrate_bps = kScreenshareTl0BitrateBps;
+    stream.target_bitrate_bps = kScreenshareCodecTargetBitrateBps;
     stream.max_bitrate_bps = 1000000;
     stream.max_framerate = kScreenshareDefaultFramerate;
     stream.num_temporal_layers = 2;
@@ -174,6 +175,23 @@ TEST_F(VideoCodecInitializerTest, SingleStreamVp8ScreenshareInactive) {
   EXPECT_EQ(0U, bitrate_allocation.get_sum_bps());
 }
 
+TEST_F(VideoCodecInitializerTest, TemporalLayeredVp8ScreenshareConference) {
+  SetUpFor(VideoCodecType::kVideoCodecVP8, 1, 2, true);
+  streams_.push_back(DefaultScreenshareStream());
+  EXPECT_TRUE(InitializeCodec());
+  bitrate_allocator_->SetLegacyConferenceMode(true);
+
+  EXPECT_EQ(1u, codec_out_.numberOfSimulcastStreams);
+  EXPECT_EQ(2u, codec_out_.VP8()->numberOfTemporalLayers);
+  VideoBitrateAllocation bitrate_allocation =
+      bitrate_allocator_->Allocate(VideoBitrateAllocationParameters(
+          kScreenshareCodecTargetBitrateBps, kScreenshareDefaultFramerate));
+  EXPECT_EQ(kScreenshareCodecTargetBitrateBps,
+            bitrate_allocation.get_sum_bps());
+  EXPECT_EQ(kScreenshareConferenceTl0BitrateBps,
+            bitrate_allocation.GetBitrate(0, 0));
+}
+
 TEST_F(VideoCodecInitializerTest, TemporalLayeredVp8Screenshare) {
   SetUpFor(VideoCodecType::kVideoCodecVP8, 1, 2, true);
   streams_.push_back(DefaultScreenshareStream());

video/video_stream_encoder.cc

@@ -780,6 +780,8 @@ void VideoStreamEncoder::ReconfigureEncoder() {
 
   rate_allocator_ =
       settings_.bitrate_allocator_factory->CreateVideoBitrateAllocator(codec);
+  rate_allocator_->SetLegacyConferenceMode(
+      encoder_config_.legacy_conference_mode);
 
   // Reset (release existing encoder) if one exists and anything except
   // start bitrate or max framerate has changed.