Reland "When VP9 SVC is used, use SvcConfig to set max bitrate for the stream."

This is a reland of commit 3afb8e24311dc1297150d4011894b6cb00841735

Patchset 1 is the original CL. Patchset 2 contains a fix:
Depending on call site, the number of spatial layers for VP9 might be
signalled in three different ways. One of them was afaict only used in
out perf tests, and resulted in the max bitrate being incorrectly
capped.
The fix now checks that field too.

Original change's description:
> When VP9 SVC is used, use SvcConfig to set max bitrate for the stream.
>
> Currently, a default max bitrate is determined within WebRtcVideoEngine,
> which maxes out at 2.5Mbps - and that limits the max bitrate deteremined
> by SvcConfig for resolutions above 720p.
>
> This does not affect simulcast, as WebRtcVideoEngine already knows to
> trust the rate allocation in simulcast.cc instead.
>
> Bug: webrtc:14017
> Change-Id: I0c310a6fd496e9e5a10eae45838900068aa1ae2d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267160
> Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#37370}

Bug: webrtc:14017, webrtc:14234
Change-Id: Idcaf4321a20c917e4049522c577336ddcfc7ffbb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267860
Auto-Submit: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37446}

media/BUILD.gn

@@ -305,6 +305,7 @@ rtc_library("rtc_audio_video") {
     "../modules/video_coding",
     "../modules/video_coding:video_codec_interface",
     "../modules/video_coding:video_coding_utility",
+    "../modules/video_coding:webrtc_vp9_helpers",
     "../modules/video_coding/svc:scalability_mode_util",
     "../rtc_base",
     "../rtc_base:audio_format_to_string",

media/engine/webrtc_video_engine.cc

@@ -32,6 +32,7 @@
 #include "media/engine/webrtc_media_engine.h"
 #include "media/engine/webrtc_voice_engine.h"
 #include "modules/rtp_rtcp/source/rtp_util.h"
+#include "modules/video_coding/codecs/vp9/svc_config.h"
 #include "modules/video_coding/svc/scalability_mode_util.h"
 #include "rtc_base/copy_on_write_buffer.h"
 #include "rtc_base/experiments/field_trial_parser.h"
@@ -3638,6 +3639,44 @@ EncoderStreamFactory::CreateDefaultVideoStreams(
         kMinLayerSize);
   }
 
+  if (absl::EqualsIgnoreCase(codec_name_, kVp9CodecName)) {
+    RTC_DCHECK(encoder_config.encoder_specific_settings);
+    // Use VP9 SVC layering from codec settings which might be initialized
+    // though field trial in ConfigureVideoEncoderSettings.
+    webrtc::VideoCodecVP9 vp9_settings;
+    encoder_config.encoder_specific_settings->FillVideoCodecVp9(&vp9_settings);
+    layer.num_temporal_layers = vp9_settings.numberOfTemporalLayers;
+
+    // Number of spatial layers is signalled differently from different call
+    // sites (sigh), pick the max as we are interested in the upper bound.
+    int num_spatial_layers =
+        std::max({encoder_config.simulcast_layers.size(),
+                  encoder_config.spatial_layers.size(),
+                  size_t{vp9_settings.numberOfSpatialLayers}});
+
+    if (width * height > 0 &&
+        (layer.num_temporal_layers > 1u || num_spatial_layers > 1)) {
+      // In SVC mode, the VP9 max bitrate is determined by SvcConfig, instead of
+      // GetMaxDefaultVideoBitrateKbps().
+      std::vector<webrtc::SpatialLayer> svc_layers =
+          webrtc::GetSvcConfig(width, height, max_framerate,
+                               /*first_active_layer=*/0, num_spatial_layers,
+                               *layer.num_temporal_layers, is_screenshare_);
+      int sum_max_bitrates_kbps = 0;
+      for (const webrtc::SpatialLayer& spatial_layer : svc_layers) {
+        sum_max_bitrates_kbps += spatial_layer.maxBitrate;
+      }
+      RTC_DCHECK_GE(sum_max_bitrates_kbps, 0);
+      if (encoder_config.max_bitrate_bps <= 0) {
+        max_bitrate_bps = sum_max_bitrates_kbps * 1000;
+      } else {
+        max_bitrate_bps =
+            std::min(max_bitrate_bps, sum_max_bitrates_kbps * 1000);
+      }
+      max_bitrate_bps = std::max(min_bitrate_bps, max_bitrate_bps);
+    }
+  }
+
   // In the case that the application sets a max bitrate that's lower than the
   // min bitrate, we adjust it down (see bugs.webrtc.org/9141).
   layer.min_bitrate_bps = std::min(min_bitrate_bps, max_bitrate_bps);
@@ -3651,15 +3690,6 @@ EncoderStreamFactory::CreateDefaultVideoStreams(
   layer.max_qp = max_qp_;
   layer.bitrate_priority = encoder_config.bitrate_priority;
 
-  if (absl::EqualsIgnoreCase(codec_name_, kVp9CodecName)) {
-    RTC_DCHECK(encoder_config.encoder_specific_settings);
-    // Use VP9 SVC layering from codec settings which might be initialized
-    // though field trial in ConfigureVideoEncoderSettings.
-    webrtc::VideoCodecVP9 vp9_settings;
-    encoder_config.encoder_specific_settings->FillVideoCodecVp9(&vp9_settings);
-    layer.num_temporal_layers = vp9_settings.numberOfTemporalLayers;
-  }
-
   if (IsTemporalLayersSupported(codec_name_)) {
     // Use configured number of temporal layers if set.
     if (encoder_config.simulcast_layers[0].num_temporal_layers) {

media/engine/webrtc_video_engine_unittest.cc

@@ -70,9 +70,11 @@
 using ::testing::_;
 using ::testing::Contains;
 using ::testing::Each;
+using ::testing::ElementsAre;
 using ::testing::ElementsAreArray;
 using ::testing::Eq;
 using ::testing::Field;
+using ::testing::Gt;
 using ::testing::IsEmpty;
 using ::testing::Pair;
 using ::testing::Return;
@@ -3732,6 +3734,52 @@ TEST_F(Vp9SettingsTest, AllEncodingParametersCopied) {
   EXPECT_TRUE(encoder_config.simulcast_layers[2].active);
 }
 
+TEST_F(Vp9SettingsTest, MaxBitrateDeterminedBySvcResolutions) {
+  cricket::VideoSendParameters parameters;
+  parameters.codecs.push_back(GetEngineCodec("VP9"));
+  ASSERT_TRUE(channel_->SetSendParameters(parameters));
+
+  std::vector<uint32_t> ssrcs = MAKE_VECTOR(kSsrcs3);
+
+  FakeVideoSendStream* stream =
+      AddSendStream(CreateSimStreamParams("cname", ssrcs));
+
+  webrtc::VideoSendStream::Config config = stream->GetConfig().Copy();
+
+  webrtc::test::FrameForwarder frame_forwarder;
+  EXPECT_TRUE(channel_->SetVideoSend(ssrcs[0], nullptr, &frame_forwarder));
+  channel_->SetSend(true);
+
+  // Send frame at 1080p@30fps.
+  frame_forwarder.IncomingCapturedFrame(frame_source_.GetFrame(
+      1920, 1080, webrtc::VideoRotation::kVideoRotation_0,
+      /*duration_us=*/33000));
+
+  webrtc::VideoCodecVP9 vp9_settings;
+  ASSERT_TRUE(stream->GetVp9Settings(&vp9_settings)) << "No VP9 config set.";
+
+  const size_t kNumSpatialLayers = ssrcs.size();
+  const size_t kNumTemporalLayers = 3;
+  EXPECT_EQ(vp9_settings.numberOfSpatialLayers, kNumSpatialLayers);
+  EXPECT_EQ(vp9_settings.numberOfTemporalLayers, kNumTemporalLayers);
+
+  EXPECT_TRUE(channel_->SetVideoSend(ssrcs[0], nullptr, nullptr));
+
+  // VideoStream max bitrate should be more than legacy 2.5Mbps default stream
+  // cap.
+  EXPECT_THAT(
+      stream->GetVideoStreams(),
+      ElementsAre(Field(&webrtc::VideoStream::max_bitrate_bps, Gt(2500000))));
+
+  // Update send parameters to 2Mbps, this should cap the max bitrate of the
+  // stream.
+  parameters.max_bandwidth_bps = 2000000;
+  channel_->SetSendParameters(parameters);
+  EXPECT_THAT(
+      stream->GetVideoStreams(),
+      ElementsAre(Field(&webrtc::VideoStream::max_bitrate_bps, Eq(2000000))));
+}
+
 class Vp9SettingsTestWithFieldTrial
     : public Vp9SettingsTest,
       public ::testing::WithParamInterface<