To mitigate some problems of
pixel color mapping used in SLHDR type of HDR
video decoding, we teach a
high dynamic range video encoding circuit (300) configured to
encode a
high dynamic range image (IM HDR) having a first
maximum pixel luminance (PB CI) with a second image (Im LWRDR) having a lower
dynamic range and a corresponding lower second
maximum pixel luminance (PB C2), the second image being functionally encoded as a luminance mapping function (400) for a decoder to apply to pixel luminances (Y PQ) of the
high dynamic range image to obtain corresponding pixel luminances (PO) of the second image, the
encoder comprising a data formatter (304) configured to output the high
dynamic range image and
metadata (MET) encoding the luminance mapping function (400) to a video communication medium (399), the functional encoding of the second image being further based on a color
lookup table (CL(Y PQ)) encoding a multiplier constant (B) for all possible values of pixel luminances of the high
dynamic range image, and the formatter being configured to output this color
lookup table in the
metadata, characterized in that the
high dynamic range video encoding circuit comprises a
gain determination circuit (302) configured to determine luminance
gain values (G PQ) quantifying a ratio of output image luminances equal to a luminance position of a correct normalized luminance position divided by output luminances of luminances of pixels of the high dynamic range image, wherein the
high dynamic range video encoding circuit comprises a color
lookup table determination circuit (303) configured to determine the color lookup table (CL(Y PQ)) based on values of the luminance
gain values for various luminances of pixels present in the high dynamic range image. Similarly, we teach how to embody the same principles in a SLHDR type of
video decoder.