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using "correct" colourimetry

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minjaesong
2025-09-15 10:14:44 +09:00
parent 34cf5cb591
commit ded609e65e
2 changed files with 17 additions and 7 deletions
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18
video_encoder/encoder_tev.c
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@@ -352,18 +352,28 @@ static inline double HLG_inverse_OETF(double V) {
}
// ---------------------- Matrices (doubles) ----------------------
// linear RGB -> LMS (technically we should convert sRGB to Rec.2100, but if encoder and decoder agrees on the same colourimetry, this utilises more bits
static const double M_RGB_TO_LMS[3][3] = {
// linear RGB -> XYZ -> Rec.2100 -> LMS
/*static const double M_RGB_TO_LMS[3][3] = {
{1688.0/4096.0,2146.0/4096.0, 262.0/4096.0},
{ 683.0/4096.0,2951.0/4096.0, 462.0/4096.0},
{ 99.0/4096.0, 309.0/4096.0,3688.0/4096.0}
};*/
static const double M_RGB_TO_LMS[3][3] = {
{0.2958564579364564, 0.6230869483219083, 0.08106989398623762},
{0.15627390752659093, 0.727308963512872, 0.11639736914944238},
{0.035141262332177715, 0.15657109121101628, 0.8080956851990795}
};
// Inverse: LMS -> linear sRGB (inverse of above)
static const double M_LMS_TO_RGB[3][3] = {
/*static const double M_LMS_TO_RGB[3][3] = {
{3.436606694333079, -2.5064521186562705, 0.06984542432319149},
{-0.7913295555989289, 1.983600451792291, -0.192270896193362},
{-0.025949899690592665, -0.09891371471172647, 1.1248636144023192}
};*/
static const double M_LMS_TO_RGB[3][3] = {
{6.1723815689243215, -5.319534979827695, 0.14699442094633924},
{-1.3243428148026244, 2.560286104841917, -0.2359203727576164},
{-0.011819739235953752, -0.26473549971186555, 1.2767952602537955}
};
// ICtCp matrix (L' M' S' -> I Ct Cp). Values are the BT.2100 integer-derived /4096 constants.
@@ -2785,7 +2795,7 @@ int main(int argc, char *argv[]) {
if (enc->ictcp_mode) {
// ICtCp: Ct and Cp have different characteristics than YCoCg Co/Cg
// Cp channel now uses specialized quantization table, so moderate quality is fine
int base_chroma_quality = (enc->qualityCo + enc->qualityCg) >> 1;
int base_chroma_quality = enc->qualityCo;
enc->qualityCo = base_chroma_quality; // Ct channel: keep original Co quantization
enc->qualityCg = base_chroma_quality; // Cp channel: same quality since Q_Cp_8 handles detail preservation
}