commit 8face53ab54e08cb5fb155f3a531818404be9295
author Alec Mouri <alecmouri@google.com> Sat Nov 09 22:15:32 2024 +0000
committer Alec Mouri <alecmouri@google.com> Mon Nov 18 17:50:13 2024 +0000
tree 4bee39249265ec55d229fffe2c475c312e319bee
parent 4fabc0119c8f18e3997c00543831141e6647ba1c

Limit HLG to 4.926x SDR

HLG is universally too bright on basically every single platform that
supports HDR. Fix this for Android.

Bug: 362510107
Flag: com.android.graphics.surfaceflinger.flags.begone_bright_hlg
Test: HLG playback
Change-Id: I5d464c016be62b11f6a3cc1ab228e14d198afb15

services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp

diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index f6d9a1a..bb01946 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -26,6 +26,7 @@
 #include <ui/FloatRect.h>
 #include <ui/HdrRenderTypeUtils.h>
 #include <cstdint>
+#include <limits>
 #include "system/graphics-base-v1.0.h"
 
 #include <com_android_graphics_libgui_flags.h>
@@ -398,11 +399,22 @@
     // For hdr content, treat the white point as the display brightness - HDR content should not be
     // boosted or dimmed.
     // If the layer explicitly requests to disable dimming, then don't dim either.
-    if (hdrRenderType == HdrRenderType::GENERIC_HDR ||
-        getOutput().getState().displayBrightnessNits == getOutput().getState().sdrWhitePointNits ||
-        getOutput().getState().displayBrightnessNits == 0.f || !layerFEState->dimmingEnabled) {
+    if (getOutput().getState().displayBrightnessNits == getOutput().getState().sdrWhitePointNits ||
+        getOutput().getState().displayBrightnessNits <= 0.f || !layerFEState->dimmingEnabled) {
         state.dimmingRatio = 1.f;
         state.whitePointNits = getOutput().getState().displayBrightnessNits;
+    } else if (hdrRenderType == HdrRenderType::GENERIC_HDR) {
+        float deviceHeadroom = getOutput().getState().displayBrightnessNits /
+                getOutput().getState().sdrWhitePointNits;
+        float idealizedMaxHeadroom = deviceHeadroom;
+
+        if (FlagManager::getInstance().begone_bright_hlg()) {
+            idealizedMaxHeadroom =
+                    std::min(idealizedMaxHeadroom, getIdealizedMaxHeadroom(state.dataspace));
+        }
+
+        state.dimmingRatio = std::min(idealizedMaxHeadroom / deviceHeadroom, 1.0f);
+        state.whitePointNits = getOutput().getState().displayBrightnessNits * state.dimmingRatio;
     } else {
         float layerBrightnessNits = getOutput().getState().sdrWhitePointNits;
         // RANGE_EXTENDED can "self-promote" to HDR, but is still rendered for a particular