From 1ad51fe73c2e05e66e92c8168dc4314f3be46757 Mon Sep 17 00:00:00 2001
From: Qiu Jianlin <jianlin.qiu@intel.com>
Date: Sat, 8 Feb 2025 10:12:04 +0800
Subject: [PATCH] Use similar bitrate allocations as VP9 for H.265 simulcast
 streams.
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Now that there is not requirement of base-heavy for H.265 simulcast, it
should follow VP9 on simulcast bitrate allocations per stream.

Bug: chromium:392060821
Change-Id: I245def7f27022a943a31e96a51552db7505b7546
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/376620
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43865}
---
 video/config/simulcast.cc          |  2 +-
 video/config/simulcast_unittest.cc | 45 ++++++++++++++++++++++++++++++
 video/video_stream_encoder.cc      |  3 ++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/video/config/simulcast.cc b/video/config/simulcast.cc
index 4391d973f6..0893b4ca90 100644
--- a/video/config/simulcast.cc
+++ b/video/config/simulcast.cc
@@ -320,7 +320,7 @@ std::vector<webrtc::VideoStream> GetNormalSimulcastLayers(
           // Base heavy allocation increases TL0 bitrate from 40% to 60%.
           rate_factor = 0.4 / 0.6;
         }
-      } else {
+      } else if (num_temporal_layers > 3) {
         rate_factor =
             webrtc::SimulcastRateAllocator::GetTemporalRateAllocation(
                 3, 0, /*base_heavy_tl3_rate_alloc=*/false) /
diff --git a/video/config/simulcast_unittest.cc b/video/config/simulcast_unittest.cc
index f538cd7de7..cc9386c7a7 100644
--- a/video/config/simulcast_unittest.cc
+++ b/video/config/simulcast_unittest.cc
@@ -22,6 +22,7 @@ using ::testing::SizeIs;
 
 constexpr bool kScreenshare = true;
 constexpr int kDefaultTemporalLayers = 3;  // Value from simulcast.cc.
+constexpr int kDefaultH265TemporalLayers = 1;  // Value from simulcast.cc.
 
 // Values from kSimulcastConfigs in simulcast.cc.
 const std::vector<VideoStream> GetSimulcastBitrates720p() {
@@ -38,6 +39,21 @@ const std::vector<VideoStream> GetSimulcastBitrates720p() {
   return streams;
 }
 
+// Values from kSimulcastFormatsH265 in simulcast.cc
+const std::vector<VideoStream> GetH265SimulcastBitrates720p() {
+  std::vector<VideoStream> streams(3);
+  streams[0].min_bitrate_bps = 30'000;
+  streams[0].target_bitrate_bps = 142'000;
+  streams[0].max_bitrate_bps = 142'000;
+  streams[1].min_bitrate_bps = 193'000;
+  streams[1].target_bitrate_bps = 420'000;
+  streams[1].max_bitrate_bps = 420'000;
+  streams[2].min_bitrate_bps = 481'000;
+  streams[2].target_bitrate_bps = 1'524'000;
+  streams[2].max_bitrate_bps = 1'524'000;
+  return streams;
+}
+
 // Creates a vector of resolutions scaled down with 1/2 factor ordered from low
 // to high.
 std::vector<Resolution> CreateResolutions(int max_width,
@@ -121,6 +137,35 @@ TEST(SimulcastTest, GetConfig) {
   }
 }
 
+TEST(SimulcastTest, GetConfigH265) {
+  const ExplicitKeyValueConfig trials("");
+  const std::vector<VideoStream> kExpected = GetH265SimulcastBitrates720p();
+
+  const size_t kMaxLayers = 3;
+  std::vector<VideoStream> streams = cricket::GetSimulcastConfig(
+      CreateResolutions(1280, 720, kMaxLayers), !kScreenshare, true, trials,
+      webrtc::kVideoCodecH265);
+
+  ASSERT_THAT(streams, SizeIs(kMaxLayers));
+  EXPECT_EQ(320u, streams[0].width);
+  EXPECT_EQ(180u, streams[0].height);
+  EXPECT_EQ(640u, streams[1].width);
+  EXPECT_EQ(360u, streams[1].height);
+  EXPECT_EQ(1280u, streams[2].width);
+  EXPECT_EQ(720u, streams[2].height);
+
+  for (size_t i = 0; i < streams.size(); ++i) {
+    EXPECT_EQ(size_t{kDefaultH265TemporalLayers},
+              streams[i].num_temporal_layers);
+    EXPECT_EQ(cricket::kDefaultVideoMaxFramerate, streams[i].max_framerate);
+    EXPECT_EQ(-1, streams[i].max_qp);
+    EXPECT_EQ(kExpected[i].min_bitrate_bps, streams[i].min_bitrate_bps);
+    EXPECT_EQ(kExpected[i].target_bitrate_bps, streams[i].target_bitrate_bps);
+    EXPECT_EQ(kExpected[i].max_bitrate_bps, streams[i].max_bitrate_bps);
+    EXPECT_TRUE(streams[i].active);
+  }
+}
+
 TEST(SimulcastTest, GetConfigWithBaseHeavyVP8TL3RateAllocation) {
   ExplicitKeyValueConfig trials(
       "WebRTC-UseBaseHeavyVP8TL3RateAllocation/Enabled/");
diff --git a/video/video_stream_encoder.cc b/video/video_stream_encoder.cc
index a7e24400fb..5f5c3a9e43 100644
--- a/video/video_stream_encoder.cc
+++ b/video/video_stream_encoder.cc
@@ -92,6 +92,9 @@ int GetNumSpatialLayers(const VideoCodec& codec) {
   } else if (codec.codecType == kVideoCodecAV1 &&
              codec.GetScalabilityMode().has_value()) {
     return ScalabilityModeToNumSpatialLayers(*(codec.GetScalabilityMode()));
+  } else if (codec.codecType == kVideoCodecH265) {
+    // No spatial scalability support for H.265.
+    return 1;
   } else {
     return 0;
   }