From 9bbd4d34e99de30bdf9fd5b5b2fba0b4e616597b Mon Sep 17 00:00:00 2001
From: Philipp Hancke <phancke@meta.com>
Date: Thu, 6 Feb 2025 14:42:59 -0800
Subject: [PATCH] Pick H265 payload type from lower dynamic PT range
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as the "upper range" is already filled and new codecs should prefer the
lower dynamic PT range.

drive-by: restore audio/red behavior too even though in practice it has
not changed.

BUG=chromium:391903235

Change-Id: Iefc78253bf0fe88567f9032059ead3c2557e36a1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/376520
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@meta.com>
Cr-Commit-Position: refs/heads/main@{#43866}
---
 call/payload_type_picker.cc          |  5 +++--
 call/payload_type_picker_unittest.cc | 21 ++++++++++++++++++---
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/call/payload_type_picker.cc b/call/payload_type_picker.cc
index c7983ce172..5c80f5808b 100644
--- a/call/payload_type_picker.cc
+++ b/call/payload_type_picker.cc
@@ -54,10 +54,11 @@ struct MapTableEntry {
 bool CodecPrefersLowerRange(const cricket::Codec& codec) {
   // All audio codecs prefer upper range.
   if (codec.type == cricket::Codec::Type::kAudio) {
-    return false;
+    return absl::EqualsIgnoreCase(codec.name, cricket::kRedCodecName);
   }
   if (absl::EqualsIgnoreCase(codec.name, cricket::kFlexfecCodecName) ||
-      absl::EqualsIgnoreCase(codec.name, cricket::kAv1CodecName)) {
+      absl::EqualsIgnoreCase(codec.name, cricket::kAv1CodecName) ||
+      absl::EqualsIgnoreCase(codec.name, cricket::kH265CodecName)) {
     return true;
   } else if (absl::EqualsIgnoreCase(codec.name, cricket::kH264CodecName)) {
     std::string profile_level_id;
diff --git a/call/payload_type_picker_unittest.cc b/call/payload_type_picker_unittest.cc
index 5a3e39bb5b..a1f89e4e7f 100644
--- a/call/payload_type_picker_unittest.cc
+++ b/call/payload_type_picker_unittest.cc
@@ -21,6 +21,7 @@ namespace webrtc {
 
 using testing::Eq;
 using testing::Ge;
+using testing::Le;
 using testing::Lt;
 using testing::Ne;
 
@@ -189,6 +190,14 @@ TEST(PayloadTypePicker, AudioGetsHigherRange) {
   EXPECT_THAT(result, Ge(96));
 }
 
+TEST(PayloadTypePicker, AudioRedGetsLowerRange) {
+  PayloadTypePicker picker;
+  cricket::Codec an_audio_codec =
+      cricket::CreateAudioCodec(-1, "red", 48000, 2);
+  auto result = picker.SuggestMapping(an_audio_codec, nullptr).value();
+  EXPECT_THAT(result, Le(63));
+}
+
 TEST(PayloadTypePicker, VideoGetsTreatedSpecially) {
   PayloadTypePicker picker;
   cricket::Codec h264_constrained = cricket::CreateVideoCodec(SdpVideoFormat(
@@ -203,17 +212,23 @@ TEST(PayloadTypePicker, VideoGetsTreatedSpecially) {
       {cricket::kVp9CodecName, {{cricket::kVP9ProfileId, "2"}}}));
   cricket::Codec vp9_profile_3 = cricket::CreateVideoCodec(SdpVideoFormat(
       {cricket::kVp9CodecName, {{cricket::kVP9ProfileId, "3"}}}));
+  cricket::Codec h265 = cricket::CreateVideoCodec(SdpVideoFormat(
+      cricket::kH265CodecName, {{cricket::kH265FmtpProfileId, "1"},
+                                {cricket::kH265FmtpTierFlag, "0"},
+                                {cricket::kH265FmtpLevelId, "93"},
+                                {cricket::kH265FmtpTxMode, "SRST"}}));
   // Valid for high range only.
   EXPECT_THAT(picker.SuggestMapping(h264_constrained, nullptr).value(), Ge(96));
   EXPECT_THAT(picker.SuggestMapping(vp9_profile_2, nullptr).value(), Ge(96));
   // Valid for lower range.
-  EXPECT_THAT(picker.SuggestMapping(h264_yuv444, nullptr).value(), Lt(63));
-  EXPECT_THAT(picker.SuggestMapping(vp9_profile_3, nullptr).value(), Lt(63));
+  EXPECT_THAT(picker.SuggestMapping(h264_yuv444, nullptr).value(), Le(63));
+  EXPECT_THAT(picker.SuggestMapping(vp9_profile_3, nullptr).value(), Le(63));
+  EXPECT_THAT(picker.SuggestMapping(h265, nullptr).value(), Le(63));
 
   // RTX with a primary codec in the lower range is valid for lower range.
   cricket::Codec lower_range_rtx =
       cricket::CreateVideoRtxCodec(cricket::Codec::kIdNotSet, 63);
-  EXPECT_THAT(picker.SuggestMapping(lower_range_rtx, nullptr).value(), Lt(63));
+  EXPECT_THAT(picker.SuggestMapping(lower_range_rtx, nullptr).value(), Le(63));
 }
 
 TEST(PayloadTypePicker, ChoosingH264Profiles) {