Support 10- and 12-bit Y'CbCr output.

[movit] / ycbcr.cpp

diff --git a/ycbcr.cpp b/ycbcr.cpp
index 50059125dc4a3c866dff4ef08e82916d94ff7a43..eaa2ee8c3bb277903bef8ab7a8a33f6c137aecf1 100644 (file)
--- a/ycbcr.cpp
+++ b/ycbcr.cpp
@@ -89,25 +89,26 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
                assert(false);
        }
 
+       const int num_levels = ycbcr_format.num_levels;
        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.