X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=ycbcr.cpp;h=dc223e7441c845cf7c1449e439862c5732efc71f;hp=f0124eaab178048a2ae3a00c758355fa275668a2;hb=5f81c29e307735bbadb3c0cb06500af627b2e57a;hpb=ba60914d4e5eda7b28af700bf43e9699b7aa720d

diff --git a/ycbcr.cpp b/ycbcr.cpp
index f0124ea..dc223e7 100644
--- a/ycbcr.cpp
+++ b/ycbcr.cpp
@@ -1,3 +1,6 @@
+// Note: This file does not have its own unit test; it is tested mainly
+// through YCbCrInput's unit tests.
+
 #include <Eigen/Core>
 #include <Eigen/LU>
 
@@ -45,7 +48,12 @@ namespace movit {
 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
 {
 	float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
-	return (0.5 - local_chroma_pos) / resolution;
+	if (fabs(local_chroma_pos - 0.5) < 1e-10) {
+		// x + (-0) can be optimized away freely, as opposed to x + 0.
+		return -0.0;
+	} else {
+		return (0.5 - local_chroma_pos) / resolution;
+	}
 }
 
 // Given <ycbcr_format>, compute the values needed to turn Y'CbCr into R'G'B';
@@ -82,6 +90,7 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
 	}
 
 	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;
@@ -91,6 +100,7 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
 		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;