From 216cce5f49fb33a26aba6ddfbad24697d91973dc Mon Sep 17 00:00:00 2001
From: Johannes Kron <kron@webrtc.org>
Date: Wed, 26 Jun 2024 19:22:19 +0200
Subject: [PATCH] Add minimum_qp to VideoEncoder::EncoderInfo
MIME-Version: 1.0
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The minimum QP field will be used to signal what the QP value will be
once the encoder reach its target video quality. This will be used
in the generalized QP convergence detection.

Bug: chromium:328598314
Change-Id: I82299cd921e3c091e651218d1e3f337875176567
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/355701
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Markus Handell <handellm@google.com>
Cr-Commit-Position: refs/heads/main@{#42559}
---
 api/video_codecs/video_encoder.h                      | 5 +++++
 modules/video_coding/codecs/av1/libaom_av1_encoder.cc | 4 ++++
 modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc | 5 +++++
 modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc | 4 ++++
 4 files changed, 18 insertions(+)

diff --git a/api/video_codecs/video_encoder.h b/api/video_codecs/video_encoder.h
index 49ea6e1c0e..1fcde28fdc 100644
--- a/api/video_codecs/video_encoder.h
+++ b/api/video_codecs/video_encoder.h
@@ -259,6 +259,11 @@ class RTC_EXPORT VideoEncoder {
     // Indicates whether or not QP value encoder writes into frame/slice/tile
     // header can be interpreted as average frame/slice/tile QP.
     absl::optional<bool> is_qp_trusted;
+
+    // The minimum QP that the encoder is expected to use with the current
+    // configuration. This may be used to determine if the encoder has reached
+    // its target video quality for static screenshare content.
+    absl::optional<int> minimum_qp;
   };
 
   struct RTC_EXPORT RateControlParameters {
diff --git a/modules/video_coding/codecs/av1/libaom_av1_encoder.cc b/modules/video_coding/codecs/av1/libaom_av1_encoder.cc
index a42c08e520..93eeddd8b2 100644
--- a/modules/video_coding/codecs/av1/libaom_av1_encoder.cc
+++ b/modules/video_coding/codecs/av1/libaom_av1_encoder.cc
@@ -59,6 +59,8 @@ namespace {
 
 // Encoder configuration parameters
 constexpr int kQpMin = 10;
+constexpr int kAv1ScreenshareMinimumQindex =
+    40;  // Min qindex corresponding to kQpMin.
 constexpr int kUsageProfile = AOM_USAGE_REALTIME;
 constexpr int kMinQindex = 145;  // Min qindex threshold for QP scaling.
 constexpr int kMaxQindex = 205;  // Max qindex threshold for QP scaling.
@@ -866,6 +868,8 @@ VideoEncoder::EncoderInfo LibaomAv1Encoder::GetEncoderInfo() const {
     info.resolution_bitrate_limits =
         encoder_info_override_.resolution_bitrate_limits();
   }
+
+  info.minimum_qp = kAv1ScreenshareMinimumQindex;
   return info;
 }
 
diff --git a/modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc b/modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc
index 6dcdbfd2c8..3d2d4821b2 100644
--- a/modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc
+++ b/modules/video_coding/codecs/vp8/libvpx_vp8_encoder.cc
@@ -68,6 +68,7 @@ constexpr char kVp8ForcePartitionResilience[] =
 // bitstream range of [0, 127] and not the user-level range of [0,63].
 constexpr int kLowVp8QpThreshold = 29;
 constexpr int kHighVp8QpThreshold = 95;
+constexpr int kVp8ScreenshareMinimumQp = 15;
 
 constexpr int kTokenPartitions = VP8_ONE_TOKENPARTITION;
 constexpr uint32_t kVp832ByteAlign = 32u;
@@ -1348,6 +1349,10 @@ VideoEncoder::EncoderInfo LibvpxVp8Encoder::GetEncoderInfo() const {
         }
       }
     }
+
+    if (codec_.mode == VideoCodecMode::kScreensharing) {
+      info.minimum_qp = kVp8ScreenshareMinimumQp;
+    }
   }
 
   return info;
diff --git a/modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc b/modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc
index cef37a9300..b9a9ffe9a9 100644
--- a/modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc
+++ b/modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc
@@ -1825,6 +1825,10 @@ VideoEncoder::EncoderInfo LibvpxVp9Encoder::GetEncoderInfo() const {
       info.preferred_pixel_formats = {VideoFrameBuffer::Type::kI420,
                                       VideoFrameBuffer::Type::kNV12};
     }
+
+    if (codec_.mode == VideoCodecMode::kScreensharing) {
+      info.minimum_qp = variable_framerate_screenshare::kMinQP;
+    }
   }
   if (!encoder_info_override_.resolution_bitrate_limits().empty()) {
     info.resolution_bitrate_limits =