Cleanup WebRTC-Vp9ExternalRefCtrl field trial

This field trial was enabled by default for a long while.

Bug: webrtc:42234783
Change-Id: If050f88a3649c43d895110f4f68160f020f854e2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/376421
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43885}

experiments/field_trials.py

@@ -886,9 +886,6 @@ POLICY_EXEMPT_FIELD_TRIALS: FrozenSet[FieldTrial] = frozenset([
     FieldTrial('WebRTC-VideoRateControl',
                42220259,
                INDEFINITE),
-    FieldTrial('WebRTC-Vp9ExternalRefCtrl',
-               42234783,
-               date(2024, 4, 1)),
     FieldTrial('WebRTC-Vp9InterLayerPred',
                NO_BUG,  # chromium:949536
                INDEFINITE),
@@ -902,7 +899,7 @@ POLICY_EXEMPT_FIELD_TRIALS: FrozenSet[FieldTrial] = frozenset([
 ])  # yapf: disable
 
 POLICY_EXEMPT_FIELD_TRIALS_DIGEST: str = \
-    '32ec47da125c13ceb01a908627c7c10aada3d4dd'
+    '936929707bc1d3db75b6702394ca3b69ef328410'
 
 REGISTERED_FIELD_TRIALS: FrozenSet[FieldTrial] = ACTIVE_FIELD_TRIALS.union(
     POLICY_EXEMPT_FIELD_TRIALS)

modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc

@@ -274,7 +274,6 @@ LibvpxVp9Encoder::LibvpxVp9Encoder(const Environment& env,
           "WebRTC-Vp9IssueKeyFrameOnLayerDeactivation")),
       is_svc_(false),
       inter_layer_pred_(InterLayerPredMode::kOn),
-      external_ref_control_(false),  // Set in InitEncode because of tests.
       trusted_rate_controller_(RateControlSettings(env.field_trials())
                                    .LibvpxVp9TrustedRateController()),
       first_frame_in_picture_(true),
@@ -285,8 +284,6 @@ LibvpxVp9Encoder::LibvpxVp9Encoder(const Environment& env,
       is_flexible_mode_(false),
       variable_framerate_controller_(variable_framerate_screenshare::kMinFps),
       quality_scaler_experiment_(ParseQualityScalerConfig(env.field_trials())),
-      external_ref_ctrl_(
-          !env.field_trials().IsDisabled("WebRTC-Vp9ExternalRefCtrl")),
       performance_flags_(ParsePerformanceFlagsFromTrials(env.field_trials())),
       num_steady_state_frames_(0),
       config_changed_(true),
@@ -687,13 +684,6 @@ int LibvpxVp9Encoder::InitEncode(const VideoCodec* inst,
     return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
   }
 
-  // External reference control is required for different frame rate on spatial
-  // layers because libvpx generates rtp incompatible references in this case.
-  external_ref_control_ = external_ref_ctrl_ ||
-                          (num_spatial_layers_ > 1 &&
-                           codec_.mode == VideoCodecMode::kScreensharing) ||
-                          inter_layer_pred_ == InterLayerPredMode::kOn;
-
   if (num_temporal_layers_ == 1) {
     gof_.SetGofInfoVP9(kTemporalStructureMode1);
     config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_NOLAYERING;
@@ -726,14 +716,12 @@ int LibvpxVp9Encoder::InitEncode(const VideoCodec* inst,
     return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
   }
 
-  if (external_ref_control_) {
+  config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_BYPASS;
-    config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_BYPASS;
+  if (num_temporal_layers_ > 1 && num_spatial_layers_ > 1 &&
-    if (num_temporal_layers_ > 1 && num_spatial_layers_ > 1 &&
+      codec_.mode == VideoCodecMode::kScreensharing) {
-        codec_.mode == VideoCodecMode::kScreensharing) {
+    // External reference control for several temporal layers with different
-      // External reference control for several temporal layers with different
+    // frame rates on spatial layers is not implemented yet.
-      // frame rates on spatial layers is not implemented yet.
+    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
-      return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
-    }
   }
   ref_buf_ = {};
 
@@ -1207,7 +1195,7 @@ int LibvpxVp9Encoder::Encode(const VideoFrame& input_image,
     vpx_svc_ref_frame_config_t ref_config = Vp9References(layer_frames_);
     libvpx_->codec_control(encoder_, VP9E_SET_SVC_REF_FRAME_CONFIG,
                            &ref_config);
-  } else if (external_ref_control_) {
+  } else {
     vpx_svc_ref_frame_config_t ref_config =
         SetReferences(force_key_frame_, layer_id.spatial_layer_id);
 

modules/video_coding/codecs/vp9/libvpx_vp9_encoder.h

@@ -158,7 +158,6 @@ class LibvpxVp9Encoder : public VideoEncoder {
   bool layer_deactivation_requires_key_frame_;
   bool is_svc_;
   InterLayerPredMode inter_layer_pred_;
-  bool external_ref_control_;
   const bool trusted_rate_controller_;
   vpx_svc_frame_drop_t svc_drop_frame_;
   bool first_frame_in_picture_;
@@ -197,7 +196,6 @@ class LibvpxVp9Encoder : public VideoEncoder {
   } quality_scaler_experiment_;
   static QualityScalerExperiment ParseQualityScalerConfig(
       const FieldTrialsView& trials);
-  const bool external_ref_ctrl_;
 
   // Flags that can affect speed vs quality tradeoff, and are configureable per
   // resolution ranges.

modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc

@@ -735,8 +735,6 @@ TEST(Vp9ImplTest, SpatialUpswitchNotAtGOFBoundary) {
 TEST_F(TestVp9Impl, DisableEnableBaseLayerTriggersKeyFrame) {
   // Configure encoder to produce N spatial layers. Encode frames for all
   // layers. Then disable all but the last layer. Then reenable all back again.
-  test::ScopedFieldTrials override_field_trials(
-      "WebRTC-Vp9ExternalRefCtrl/Enabled/");
   const size_t num_spatial_layers = 3;
   const size_t num_temporal_layers = 3;
   // Must not be multiple of temporal period to exercise all code paths.
@@ -1954,18 +1952,14 @@ TEST_F(TestVp9Impl, EncoderInfoFpsAllocationFlexibleMode) {
 }
 
 class Vp9ImplWithLayeringTest
-    : public ::testing::TestWithParam<std::tuple<int, int, bool>> {
+    : public ::testing::TestWithParam<std::tuple<int, int>> {
  protected:
   Vp9ImplWithLayeringTest()
       : num_spatial_layers_(std::get<0>(GetParam())),
-        num_temporal_layers_(std::get<1>(GetParam())),
+        num_temporal_layers_(std::get<1>(GetParam())) {}
-        override_field_trials_(std::get<2>(GetParam())
-                                   ? "WebRTC-Vp9ExternalRefCtrl/Enabled/"
-                                   : "") {}
 
   const uint8_t num_spatial_layers_;
   const uint8_t num_temporal_layers_;
-  const test::ScopedFieldTrials override_field_trials_;
 };
 
 TEST_P(Vp9ImplWithLayeringTest, FlexibleMode) {
@@ -2032,8 +2026,7 @@ TEST_P(Vp9ImplWithLayeringTest, FlexibleMode) {
 INSTANTIATE_TEST_SUITE_P(All,
                          Vp9ImplWithLayeringTest,
                          ::testing::Combine(::testing::Values(1, 2, 3),
-                                            ::testing::Values(1, 2, 3),
+                                            ::testing::Values(1, 2, 3)));
-                                            ::testing::Bool()));
 
 class TestVp9ImplFrameDropping : public TestVp9Impl {
  protected:

test/fuzzers/vp9_encoder_references_fuzzer.cc

@@ -192,7 +192,6 @@ class FieldTrials : public FieldTrialsView {
   ~FieldTrials() override = default;
   std::string Lookup(absl::string_view key) const override {
     static constexpr absl::string_view kBinaryFieldTrials[] = {
-        "WebRTC-Vp9ExternalRefCtrl",
         "WebRTC-Vp9IssueKeyFrameOnLayerDeactivation",
     };
     for (size_t i = 0; i < ABSL_ARRAYSIZE(kBinaryFieldTrials); ++i) {

video/full_stack_tests.cc

@@ -1008,8 +1008,7 @@ TEST(FullStackTest, Vp9ksvc_3sl_Low) {
 
 TEST(FullStackTest, Vp9ksvc_3sl_Low_Bw_Limited) {
   webrtc::test::ScopedFieldTrials override_trials(
-      AppendFieldTrials("WebRTC-Vp9IssueKeyFrameOnLayerDeactivation/Enabled/"
+      AppendFieldTrials("WebRTC-Vp9IssueKeyFrameOnLayerDeactivation/Enabled/"));
-                        "WebRTC-Vp9ExternalRefCtrl/Enabled/"));
   auto fixture = CreateVideoQualityTestFixture();
   ParamsWithLogging simulcast;
   simulcast.config->link_capacity = DataRate::KilobitsPerSec(500);