+// Note: Input depths above 8 bits have not been tested, so Rec. 2020
+// support should be regarded as somewhat untested (it assumes 10-
+// or 12-bit input). We also only support “conventional non-constant
+// luminance” for Rec. 2020, where Y' is derived from R'G'B' instead of
+// RGB, since this is the same system as used in Rec. 601 and 709.
+