X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=ycbcr.h;h=207be4e98a81963aae12a86f18ff9aa8e5a9000a;hp=4eb9e73185794fc0118ec2590e4303892dfa8595;hb=a2e7b432626b8a2c54cb1ff9d09203f50227fc07;hpb=80fc4a6e806e5638ae050c3020962137ca5fd76b

diff --git a/ycbcr.h b/ycbcr.h
index 4eb9e73..207be4e 100644
--- a/ycbcr.h
+++ b/ycbcr.h
@@ -21,7 +21,7 @@
 // framebuffer, ie., the range [0.0,1.0] maps to [0,255] for 8-bit
 // and to [0,1023] (or [0_d,255.75_d] in BT.601 parlance) for 10-bit.
 //
-// BT.701 (page 5) seems to agree with BT.601; it specifies range 16–235 for
+// BT.709 (page 5) seems to agree with BT.601; it specifies range 16–235 for
 // 8-bit luma, and 64–940 for 10-bit luma. This would indicate, for a GPU,
 // that that for 8-bit mode, the range would be 16/255 to 235/255
 // (0.06275 to 0.92157), while for 10-bit, it should be 64/1023 to 940/1023
@@ -29,12 +29,17 @@
 // range, 10-bit goes out of range (white gets to 942), while if you select
 // 10-bit range, 8-bit gets only to 234, making true white impossible.
 //
-// We currently support the 8-bit ranges only, since all of our Y'CbCr
-// handling effects happen to support only 8-bit at the moment. We will need
-// to fix this eventually, though, with an added field to YCbCrFormat.
+// Thus, you will need to specify the actual precision of the Y'CbCr source
+// (or destination); the num_levels field is the right place. Most people
+// will want to simply set this to 256, as 8-bit Y'CbCr is the most common,
+// but the right value will naturally depend on your input.
+//
+// We could use unsigned formats (e.g. GL_R8UI), which in a sense would
+// solve all of this, but then we'd lose filtering.
 
 #include "image_format.h"
 
+#include <epoxy/gl.h>
 #include <Eigen/Core>
 
 namespace movit {
@@ -48,8 +53,8 @@ struct YCbCrFormat {
 	// JPEG uses the Rec. 601 luma coefficients, but full range.
 	bool full_range;
 
-	// Currently unused, but should be set to 256 for future expansion,
-	// indicating 8-bit interpretation (see file-level comment).
+	// Set to 2^n for n-bit Y'CbCr (e.g. 256 for 8-bit Y'CbCr).
+	// See file-level comment.
 	int num_levels;
 
 	// Sampling factors for chroma components. For no subsampling (4:4:4),
@@ -71,7 +76,13 @@ 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, Eigen::Matrix3d *ycbcr_to_rgb);
+//
+// <type> is the data type you're rendering from; normally, it would should match
+// <ycbcr_format.num_levels>, but for the special case of 10- and 12-bit Y'CbCr,
+// we support storing it in 16-bit formats, which incurs extra scaling factors.
+// You can get that scaling factor in <scale> if you want.
+void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float *offset, Eigen::Matrix3d *ycbcr_to_rgb,
+                          GLenum type = GL_UNSIGNED_BYTE, double *scale_factor = nullptr);
 
 }  // namespace movit