Patent EP-3764346-A1 (EP)
Inventor: NIJLAND RUTGER
IPC: G09G5/10
Filed: 2019-07-09
Abstract: To enable a better and more adjustable manner of HDR video display adaptation performed by an encoder, an image pixel luminance adaptation apparatus (500), comprises: 
- a connection (501) to a comprised or connectable video decoder (207), which video decoder is arranged to receive an encoded high dynamic range image (Im_COD), which is encoded according to a first maximum codeable luminance (PB_H), and which video decoder is arranged to receive metadata specifying at least one luma mapping function (F_ct; FL_50t1_1), which at least one luma mapping function specifies the offsets of luminances of a secondary image corresponding to the encoded high dynamic range image compared to the luminances of the same pixel positions as encoded in the encoded high dynamic range image, which secondary image has a second maximum codeable luminance (PB_S) which preferably is at least 4x smaller or larger than the first maximum codeable luminance (PB_H), and the video decoder being arranged to output a decoded high dynamic range image (Im_RHDR) and the luma mapping function; 
- a display adaptation unit (401) arranged to receive a value of a display maximum luminance (PB_D) that a particular display can display as brightest pixel color, and an input luma mapping function, and the display adaptation unit being arranged to apply an algorithm which calculates at least one display adapted luma mapping function based on the input luma mapping function and the maximum luminance (PD_D), wherein this at least one display adapted luma mapping function corresponds in shape to the input luma mapping function but lies closer to a 45 degree increasing diagonal of a graph of the input luma mapping function in perceptually uniformized axes, depending on the difference between the value of the display maximum luminance (PB_D) and the first maximum codeable luminance (PB_H) relative to the difference between the second maximum codeable luminance (PB_S) and the first maximum codeable luminance (PB_H); 
characterized in that the image pixel luminance adaptation apparatus comprises an alternative luma mapping function determination unit (502) arranged to determine an alternative luma mapping function (ALT_FL_50t1_1) and 
wherein the display adaptation unit (401) comprises a combination unit (503) which is arranged to combine the at least one luma mapping function (F_ct; FL_50t1_1) and the alternative luma mapping function (ALT_FL_50t1_1) into a combined luma mapping function (CMB_FL_50t1_1), and wherein the display adaptation unit is arranged to apply its algorithm on as input luma mapping function the combined luma mapping function; 
- the image pixel luminance adaptation apparatus comprising a luma mapping unit (510) arranged to receive pixel lumas of the decoded high dynamic range image (Im_RHDR) and to apply to those pixel lumas the combined luma mapping function to obtain output lumas of an output image (Im_DA); 
- the image pixel luminance adaptation apparatus comprising an output image or video communication cable or wireless channel, to which a display can be connected, and an output signal formatter (230) arranged to send the output image (Im_DA).