Make sure VP9 encoders are reconfigured on layer activation.

When disabling a spatial layer, reconfiguration of the encoder is not
necessary (bitrate will never be assigned to the inactive layer anway).
This CL however makes sure we reconfigure the encoder when a spatial
layer is activated. Some encoder implementations may encoder the wrong
number of spatial layers if the active layers have not beens set
correctly.

Bug: webrtc:14809, b/261097903
Change-Id: I8d34aaec95eb50a9717c06ea38f25088e5a96429
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290560
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Auto-Submit: Erik Språng <sprang@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38999}

video/video_stream_encoder.cc

@@ -150,14 +150,19 @@ bool RequiresEncoderReset(const VideoCodec& prev_send_codec,
   if (new_send_codec.codecType == kVideoCodecVP9) {
     size_t num_spatial_layers = new_send_codec.VP9().numberOfSpatialLayers;
     for (unsigned char i = 0; i < num_spatial_layers; ++i) {
+      if (!new_send_codec.spatialLayers[i].active) {
+        // No need to reset when layer is inactive.
+        continue;
+      }
       if (new_send_codec.spatialLayers[i].width !=
               prev_send_codec.spatialLayers[i].width ||
           new_send_codec.spatialLayers[i].height !=
               prev_send_codec.spatialLayers[i].height ||
           new_send_codec.spatialLayers[i].numberOfTemporalLayers !=
               prev_send_codec.spatialLayers[i].numberOfTemporalLayers ||
           new_send_codec.spatialLayers[i].qpMax !=
-              prev_send_codec.spatialLayers[i].qpMax) {
+              prev_send_codec.spatialLayers[i].qpMax ||
+          !prev_send_codec.spatialLayers[i].active) {
         return true;
       }
     }

video/video_stream_encoder_unittest.cc

@@ -8649,6 +8649,64 @@ TEST_F(VideoStreamEncoderTest,
   video_stream_encoder_->Stop();
 }
 
+TEST_F(VideoStreamEncoderTest, RecreatesEncoderWhenEnableVp9SpatialLayer) {
+  // Set up encoder to use VP9 SVC using two spatial layers.
+  fake_encoder_.SetTemporalLayersSupported(/*spatial_idx=*/0, true);
+  fake_encoder_.SetTemporalLayersSupported(/*spatial_idx*/ 1, true);
+  VideoEncoderConfig video_encoder_config;
+  test::FillEncoderConfiguration(VideoCodecType::kVideoCodecVP9,
+                                 /* num_streams*/ 1, &video_encoder_config);
+  video_encoder_config.max_bitrate_bps = 2 * kTargetBitrate.bps();
+  video_encoder_config.content_type =
+      VideoEncoderConfig::ContentType::kRealtimeVideo;
+  VideoCodecVP9 vp9_settings = VideoEncoder::GetDefaultVp9Settings();
+  vp9_settings.numberOfSpatialLayers = 2;
+  vp9_settings.numberOfTemporalLayers = 2;
+  vp9_settings.interLayerPred = InterLayerPredMode::kOn;
+  vp9_settings.automaticResizeOn = false;
+  video_encoder_config.encoder_specific_settings =
+      rtc::make_ref_counted<VideoEncoderConfig::Vp9EncoderSpecificSettings>(
+          vp9_settings);
+  video_encoder_config.spatial_layers = GetSvcConfig(1280, 720,
+                                                     /*fps=*/30.0,
+                                                     /*first_active_layer=*/0,
+                                                     /*num_spatial_layers=*/2,
+                                                     /*num_temporal_layers=*/3,
+                                                     /*is_screenshare=*/false);
+  ConfigureEncoder(video_encoder_config.Copy(),
+                   VideoStreamEncoder::BitrateAllocationCallbackType::
+                       kVideoLayersAllocation);
+
+  video_stream_encoder_->OnBitrateUpdatedAndWaitForManagedResources(
+      kTargetBitrate, kTargetBitrate, kTargetBitrate, 0, 0, 0);
+
+  video_source_.IncomingCapturedFrame(CreateFrame(CurrentTimeMs(), 1280, 720));
+  WaitForEncodedFrame(CurrentTimeMs());
+  EXPECT_EQ(fake_encoder_.GetNumInitializations(), 1);
+
+  // Turn off the top spatial layer. This does not require an encoder reset.
+  video_encoder_config.spatial_layers[1].active = false;
+  video_stream_encoder_->ConfigureEncoder(video_encoder_config.Copy(),
+                                          kMaxPayloadLength, nullptr);
+
+  time_controller_.AdvanceTime(TimeDelta::Millis(33));
+  video_source_.IncomingCapturedFrame(CreateFrame(CurrentTimeMs(), 1280, 720));
+  WaitForEncodedFrame(CurrentTimeMs());
+  EXPECT_EQ(fake_encoder_.GetNumInitializations(), 1);
+
+  // Turn on the top spatial layer again, this does require an encoder reset.
+  video_encoder_config.spatial_layers[1].active = true;
+  video_stream_encoder_->ConfigureEncoder(video_encoder_config.Copy(),
+                                          kMaxPayloadLength, nullptr);
+
+  time_controller_.AdvanceTime(TimeDelta::Millis(33));
+  video_source_.IncomingCapturedFrame(CreateFrame(CurrentTimeMs(), 1280, 720));
+  WaitForEncodedFrame(CurrentTimeMs());
+  EXPECT_EQ(fake_encoder_.GetNumInitializations(), 2);
+
+  video_stream_encoder_->Stop();
+}
+
 #endif  // !defined(WEBRTC_IOS)
 
 // Test parameters: (VideoCodecType codec, bool allow_i420_conversion)