Allow SurfaceFlinger to treat 170M as sRGB.
Introduce a debug sysprop, defaulted to false, to allow for rewriting
the transfer function to sRGB when set to true.
This is due to several considerations:
1. SurfaceFlinger has not color managed SMPTE 170M properly ever since
color management was introduced in Android O, and was only fixed in
Android 13. This means that some camera -> encoding -> storage ->
playback flows may be incorrectly calibrated on some devices since
SMPTE 170M was reinterpreted as sRGB for a long time.
2. BT. 1886 recommends a reference EOTF of gamma 2.4 with tuneable
parameters to approximate a CRT on a non-CRT display. Because the
framework doesn't support BT. 1886 and it's too late to add support,
casting as sRGB is probably okay for now and matches old behavior.
3. Typical Rec. 709 content is graded assuming a dim surround, but phone
displays are used in a wide range of viewing environments, which
means that viewing Rec. 709 content in a bright environment may
appear to have lower contrast. Decoding as sRGB will push the dark
codes into lower luminance levels, which will improve contrast in
those scenarios. Note that it's better to adjust contrast based on
the ambient viewing environment, but again it's too late for Android
13 to improve the color pipeline in the GPU.
Bug: 229442032
Test: Photos playback after recording a video
Change-Id: I64fc8f2ea77f8e595333de36fb9da2979d8316ca
diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index 3289d55..61c53df 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -322,6 +322,17 @@
? outputState.targetDataspace
: layerFEState->dataspace;
+ // Override the dataspace transfer from 170M to sRGB if the device configuration requests this.
+ // We do this here instead of in buffer info so that dumpsys can still report layers that are
+ // using the 170M transfer. Also we only do this if the colorspace is not agnostic for the
+ // layer, in case the color profile uses a 170M transfer function.
+ if (outputState.treat170mAsSrgb && !layerFEState->isColorspaceAgnostic &&
+ (state.dataspace & HAL_DATASPACE_TRANSFER_MASK) == HAL_DATASPACE_TRANSFER_SMPTE_170M) {
+ state.dataspace = static_cast<ui::Dataspace>(
+ (state.dataspace & HAL_DATASPACE_STANDARD_MASK) |
+ (state.dataspace & HAL_DATASPACE_RANGE_MASK) | HAL_DATASPACE_TRANSFER_SRGB);
+ }
+
// 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.