Use BT2100 OOTF for HLG...
...which it turns out we already do, except we apply a tone-map for
HDR10 after scaling the luminance. Don't apply the HDR10 tone-map, and
instead linearly normalize to max display luminance.
Furthermore, adjust the gamma used in the default HLG OOTF in
libshaders to take into account current display luminance according to
the BT2100 spec, which says that the OOTF gamma should be adjusted if
the effective luminance differs from 1000 nits
Bug: 208933319
Test: librenderengine_test
Test: libtonemap_test
Test: HLG and PQ test videos on youtube
Change-Id: I622096ad387420ce4769f6f080b8756cd57baa7d
diff --git a/libs/tonemap/tonemap.cpp b/libs/tonemap/tonemap.cpp
index c2372fe..bc0a884 100644
--- a/libs/tonemap/tonemap.cpp
+++ b/libs/tonemap/tonemap.cpp
@@ -407,7 +407,6 @@
)");
switch (sourceDataspaceInt & kTransferMask) {
case kTransferST2084:
- case kTransferHLG:
switch (destinationDataspaceInt & kTransferMask) {
case kTransferST2084:
program.append(R"(
@@ -428,39 +427,22 @@
break;
default:
- switch (sourceDataspaceInt & kTransferMask) {
- case kTransferST2084:
- program.append(R"(
- float libtonemap_OETFTone(float channel) {
- channel = channel / 10000.0;
- float m1 = (2610.0 / 4096.0) / 4.0;
- float m2 = (2523.0 / 4096.0) * 128.0;
- float c1 = (3424.0 / 4096.0);
- float c2 = (2413.0 / 4096.0) * 32.0;
- float c3 = (2392.0 / 4096.0) * 32.0;
-
- float tmp = pow(channel, float(m1));
- tmp = (c1 + c2 * tmp) / (1.0 + c3 * tmp);
- return pow(tmp, float(m2));
- }
- )");
- break;
- case kTransferHLG:
- program.append(R"(
- float libtonemap_OETFTone(float channel) {
- channel = channel / 1000.0;
- const float a = 0.17883277;
- const float b = 0.28466892;
- const float c = 0.55991073;
- return channel <= 1.0 / 12.0 ? sqrt(3.0 * channel) :
- a * log(12.0 * channel - b) + c;
- }
- )");
- break;
- }
// Here we're mapping from HDR to SDR content, so interpolate using a
// Hermitian polynomial onto the smaller luminance range.
program.append(R"(
+ float libtonemap_OETFTone(float channel) {
+ channel = channel / 10000.0;
+ float m1 = (2610.0 / 4096.0) / 4.0;
+ float m2 = (2523.0 / 4096.0) * 128.0;
+ float c1 = (3424.0 / 4096.0);
+ float c2 = (2413.0 / 4096.0) * 32.0;
+ float c3 = (2392.0 / 4096.0) * 32.0;
+
+ float tmp = pow(channel, float(m1));
+ tmp = (c1 + c2 * tmp) / (1.0 + c3 * tmp);
+ return pow(tmp, float(m2));
+ }
+
float libtonemap_ToneMapTargetNits(float maxRGB) {
float maxInLumi = in_libtonemap_inputMaxLuminance;
float maxOutLumi = in_libtonemap_displayMaxLuminance;
@@ -508,6 +490,30 @@
break;
}
break;
+ case kTransferHLG:
+ switch (destinationDataspaceInt & kTransferMask) {
+ // HLG -> HDR does not tone-map at all
+ case kTransferST2084:
+ case kTransferHLG:
+ program.append(R"(
+ float libtonemap_ToneMapTargetNits(float maxRGB) {
+ return maxRGB;
+ }
+ )");
+ break;
+ default:
+ // libshaders follows BT2100 OOTF, but with a nominal peak display luminance
+ // of 1000 nits. Renormalize to max display luminance if we're tone-mapping
+ // down to SDR, as libshaders normalizes all SDR output from [0,
+ // maxDisplayLumins] -> [0, 1]
+ program.append(R"(
+ float libtonemap_ToneMapTargetNits(float maxRGB) {
+ return maxRGB * in_libtonemap_displayMaxLuminance / 1000.0;
+ }
+ )");
+ break;
+ }
+ break;
default:
// Inverse tone-mapping and SDR-SDR mapping is not supported.
program.append(R"(
@@ -558,7 +564,6 @@
double targetNits = 0.0;
switch (sourceDataspaceInt & kTransferMask) {
case kTransferST2084:
- case kTransferHLG:
switch (destinationDataspaceInt & kTransferMask) {
case kTransferST2084:
targetNits = maxRGB;
@@ -587,19 +592,9 @@
double x2 = x1 + (x3 - x1) * 4.0 / 17.0;
double y2 = maxOutLumi * 0.9;
- double greyNorm1 = 0.0;
- double greyNorm2 = 0.0;
- double greyNorm3 = 0.0;
-
- if ((sourceDataspaceInt & kTransferMask) == kTransferST2084) {
- greyNorm1 = OETF_ST2084(x1);
- greyNorm2 = OETF_ST2084(x2);
- greyNorm3 = OETF_ST2084(x3);
- } else if ((sourceDataspaceInt & kTransferMask) == kTransferHLG) {
- greyNorm1 = OETF_HLG(x1);
- greyNorm2 = OETF_HLG(x2);
- greyNorm3 = OETF_HLG(x3);
- }
+ const double greyNorm1 = OETF_ST2084(x1);
+ const double greyNorm2 = OETF_ST2084(x2);
+ const double greyNorm3 = OETF_ST2084(x3);
double slope2 = (y2 - y1) / (greyNorm2 - greyNorm1);
double slope3 = (y3 - y2) / (greyNorm3 - greyNorm2);
@@ -613,12 +608,7 @@
break;
}
- double greyNits = 0.0;
- if ((sourceDataspaceInt & kTransferMask) == kTransferST2084) {
- greyNits = OETF_ST2084(targetNits);
- } else if ((sourceDataspaceInt & kTransferMask) == kTransferHLG) {
- greyNits = OETF_HLG(targetNits);
- }
+ const double greyNits = OETF_ST2084(targetNits);
if (greyNits <= greyNorm2) {
targetNits = (greyNits - greyNorm2) * slope2 + y2;
@@ -630,15 +620,20 @@
break;
}
break;
- default:
+ case kTransferHLG:
switch (destinationDataspaceInt & kTransferMask) {
case kTransferST2084:
case kTransferHLG:
- default:
targetNits = maxRGB;
break;
+ default:
+ targetNits = maxRGB * metadata.displayMaxLuminance / 1000.0;
+ break;
}
break;
+ default:
+ targetNits = maxRGB;
+ break;
}
return targetNits / maxRGB;