X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=ycbcr.cpp;h=59b7eed4eff496d31a653b0814ece809a148b3f4;hp=50059125dc4a3c866dff4ef08e82916d94ff7a43;hb=c6a0f381cca8ec937ef046e0ef0d62156fb1d7be;hpb=f71dd67f6a2abca2bb95eb3e0902f9fdcf8e8ed9

diff --git a/ycbcr.cpp b/ycbcr.cpp
index 5005912..59b7eed 100644
--- a/ycbcr.cpp
+++ b/ycbcr.cpp
@@ -59,7 +59,7 @@ float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned res
 // Given <ycbcr_format>, compute the values needed to turn Y'CbCr into R'G'B';
 // first subtract the returned offset, then left-multiply the returned matrix
 // (the scaling is already folded into it).
-void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycbcr_to_rgb)
+void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycbcr_to_rgb, GLenum type, double *scale_factor)
 {
 	double coeff[3], scale[3];
 
@@ -89,25 +89,30 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
 		assert(false);
 	}
 
+	int num_levels = ycbcr_format.num_levels;
+	if (num_levels == 0) {
+		// For the benefit of clients using old APIs, but still zeroing out the structure.
+		num_levels = 256;
+	}
 	if (ycbcr_format.full_range) {
-		// TODO: Use num_levels.
-		offset[0] = 0.0 / 255.0;
-		offset[1] = 128.0 / 255.0;
-		offset[2] = 128.0 / 255.0;
+		offset[0] = 0.0 / (num_levels - 1);
+		offset[1] = double(num_levels / 2) / (num_levels - 1);  // E.g. 128/255.
+		offset[2] = double(num_levels / 2) / (num_levels - 1);
 
 		scale[0] = 1.0;
 		scale[1] = 1.0;
 		scale[2] = 1.0;
 	} else {
-		// Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
-		// TODO: Use num_levels.
-		offset[0] = 16.0 / 255.0;
-		offset[1] = 128.0 / 255.0;
-		offset[2] = 128.0 / 255.0;
-
-		scale[0] = 255.0 / 219.0;
-		scale[1] = 255.0 / 224.0;
-		scale[2] = 255.0 / 224.0;
+		// Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 5.
+		// Rec. 2020 contains the most generic formulas, which we use here.
+		const double s = num_levels / 256.0;  // 2^(n-8) in Rec. 2020 parlance.
+		offset[0] = (s * 16.0) / (num_levels - 1);
+		offset[1] = (s * 128.0) / (num_levels - 1);
+		offset[2] = (s * 128.0) / (num_levels - 1);
+
+		scale[0] = double(num_levels - 1) / (s * 219.0);
+		scale[1] = double(num_levels - 1) / (s * 224.0);
+		scale[2] = double(num_levels - 1) / (s * 224.0);
 	}
 
 	// Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
@@ -131,6 +136,24 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
 
 	// Fold in the scaling.
 	*ycbcr_to_rgb *= Map<const Vector3d>(scale).asDiagonal();
+
+	if (type == GL_UNSIGNED_SHORT) {
+		// For 10-bit or 12-bit packed into 16-bit, we need to scale the values
+		// so that the max value goes from 1023 (or 4095) to 65535. We do this
+		// by folding the scaling into the conversion matrix, so it comes essentially
+		// for free. However, the offset is before the scaling (and thus assumes
+		// correctly scaled values), so we need to adjust that the other way.
+		double scale = 65535.0 / (ycbcr_format.num_levels - 1);
+		offset[0] /= scale;
+		offset[1] /= scale;
+		offset[2] /= scale;
+		*ycbcr_to_rgb *= scale;
+		if (scale_factor != nullptr) {
+			*scale_factor = scale;
+		}
+	} else if (scale_factor != nullptr) {
+		*scale_factor = 1.0;
+	}
 }
 
 }  // namespace movit