Merge to M86: Make VP9 correctly accept middle-layer singlecast

Unfortunate typo and week tests made it so if only a middle spatial layer
is active, vp9 encoder would be configured to send two top layers.

This is a cherry-pick of:
https://webrtc.googlesource.com/src/+/a945cdadffa50028f96449823ce6f900cd6e8b95
Original reviewed on: https://webrtc-review.googlesource.com/c/src/+/185043


Bug: webrtc:11319, chromium:1131839
Change-Id: Ia850099d8023d9ec63e27d536a546cf529bf31a4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/185184
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/branch-heads/4240@{#10}
Cr-Branched-From: 93a9d19-refs/heads/master@{#31969}

Author: Ilya Nikolaevskiy

modules/video_coding/video_codec_initializer.cc

@@ -210,7 +210,7 @@ VideoCodec VideoCodecInitializer::VideoEncoderConfigToVideoCodec(
 
         for (size_t spatial_idx = first_active_layer;
              spatial_idx < config.simulcast_layers.size() &&
-             spatial_idx < spatial_layers.size();
+             spatial_idx < spatial_layers.size() + first_active_layer;
              ++spatial_idx) {
           spatial_layers[spatial_idx - first_active_layer].active =
               config.simulcast_layers[spatial_idx].active;

modules/video_coding/video_codec_initializer_unittest.cc

@@ -364,24 +364,66 @@ TEST_F(VideoCodecInitializerTest, Vp9DeactivateLayers) {
   config_.simulcast_layers[1].active = true;
   config_.simulcast_layers[2].active = true;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_TRUE(codec_out_.spatialLayers[1].active);
   EXPECT_TRUE(codec_out_.spatialLayers[2].active);
 
   // Deactivate top layer.
+  config_.simulcast_layers[0].active = true;
+  config_.simulcast_layers[1].active = true;
   config_.simulcast_layers[2].active = false;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_TRUE(codec_out_.spatialLayers[1].active);
   EXPECT_FALSE(codec_out_.spatialLayers[2].active);
 
   // Deactivate middle layer.
-  config_.simulcast_layers[2].active = true;
+  config_.simulcast_layers[0].active = true;
   config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = true;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_FALSE(codec_out_.spatialLayers[1].active);
   EXPECT_TRUE(codec_out_.spatialLayers[2].active);
+
+  // Deactivate first layer.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = true;
+  config_.simulcast_layers[2].active = true;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 2);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_TRUE(codec_out_.spatialLayers[1].active);
+
+  // HD singlecast.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = true;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 1);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+
+  // VGA singlecast.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = true;
+  config_.simulcast_layers[2].active = false;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 2);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[1].active);
+
+  // QVGA singlecast.
+  config_.simulcast_layers[0].active = true;
+  config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = false;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[1].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[2].active);
 }
 
 }  // namespace webrtc