In a method to improve backwards compatibility when decoding high-dynamic range images coded in a wide color gamut (WCG) space which may not be compatible with legacy color spaces, hue and/or saturation values of images in an image database are computed for both a legacy color space (say, YCbCr-gamma) and a preferred WCG color space (say, IPT-PQ). Based on a cost function, a reshaped color space is computed so that the distance between the hue values in the legacy color space and rotated hue values in the preferred color space is minimized HDR images are coded in the reshaped color space. Legacy devices can still decode standard dynamic range images assuming they are coded in the legacy color space, while updated devices can use color reshaping information to decode HDR images in the preferred color space at full dynamic range.

In a method to improve backwards compatibility when decoding high-dynamic range images coded in a wide color gamut (WCG) space which may not be compatible with legacy color spaces, hue and/or saturation values of images in an image database are computed for both a legacy color space (say, YCbCr-gamma) and a preferred WCG color space (say, IPT-PQ). Based on a cost function, a reshaped color space is computed so that the distance between the hue values in the legacy color space and rotated hue values in the preferred color space is minimized HDR images are coded in the reshaped color space. Legacy devices can still decode standard dynamic range images assuming they are coded in the legacy color space, while updated devices can use color reshaping information to decode HDR images in the preferred color space at full dynamic range.

Apparatus and methods for encoding and decoding video data having improved quantization parameter prediction are presented and can include using a combination of quantization parameter prediction values obtained from respective ones of a plurality of quantization parameter prediction methods to encode or decode the video data.

Apparatus and methods for encoding and decoding video data having improved quantization parameter prediction are presented and can include using a combination of quantization parameter prediction values obtained from respective ones of a plurality of quantization parameter prediction methods to encode or decode the video data.

An example device for processing video data includes memory configured to store the video data and one or more processors coupled to the memory. The one or more processors are configured to adjust a chroma dynamic range adjustment (DRA) scale value based on a luma DRA scale value and determine a chroma quantization parameter (QP) based on the luma adjusted chroma DRA scale value, wherein the chroma QP comprises an integer component and a fractional component. The one or more processors are configured to determine an integer chroma QP offset based on the integer component and determine a fractional chroma QP offset based on the fractional component. The one or more processors are configured to determine a DRA chroma scale adjustment value based on the integer chroma QP offset and the fractional chroma QP offset and process the video data based on the DRA chroma scale adjustment value.

A method of video processing includes determining, for a conversion of a block of a video picture in a video and a bitstream representation of the video, gradients of a subset of samples in a region for a classification operation in a filtering process. The region has a dimension of M×N and the block has a dimension of K×L, M, N, K, L being positive integers. The block is located within the region. The method also includes performing the conversion based on the determining.

A method of video processing includes determining, for a conversion of a block of a video picture in a video and a bitstream representation of the video, gradients of a subset of samples in a region for a classification operation in a filtering process. The region has a dimension of M×N and the block has a dimension of K×L, M, N, K, L being positive integers. The block is located within the region. The method also includes performing the conversion based on the determining.

A method for generating at least one encoding rule to encode an image captured by an optical sensor. The method includes at least one step of reading in the image captured by the optical sensor, and a step of generating a frequency distribution of an occurrence of light-signal values at different pixels in the image. The method further includes a step of assigning code words to light-signal values, using the frequency distribution, in order to generate the at least one encoding rule for encoding the image captured by the optical sensor.

A decoding system decodes a video stream, which is encoded video information. The decoding system includes a decoder that acquires the video steam and generates decoded video information, and a maximum luminance information acquirer that acquires, in a case where a dynamic range of luminance of the video stream is a second dynamic range that is wider than a first dynamic range, maximum luminance information indicating the maximum luminance of the video stream from the video stream. The decoding system also includes an outputter that outputs the decoded video information and the maximum luminance information. Where the dynamic range of luminance of the video stream is expressed by the maximum luminance of all pictures in the video stream as the maximum luminance information, the outputter outputs the decoded video information, along with the maximum luminance information indicating the maximum luminance of all pictures in the video stream.

To enable better color and in particular color saturation control for HDR image handling systems which need to do luminance dynamic range conversion, e.g. from a SDR image to an image optimized for rendering on a display of higher display peak brightness and dynamic range, the inventors invented an apparatus (400) for processing a color saturation (C′bL, C′rL) of an input color (Y′L, C′bL, C′rL) of an input image (Im_RLDR) to yield an output color (Y′M, Cb′M, Cr′M) of an output image (Im3000nit) corresponding to the input image, which output image is a re-grading of the input image characterized by the fact that its pixel colors have a different normalized luminance position (Y2) compared to the normalized luminance positions of the input colors (Y1), the normalized luminances being defined as the luminance of a pixel divided by the respective maximal codeable luminance of the image's luminance representation, whereby the ratio of the maximum codeable luminance of the input image and the maximum codeable luminance of the output image is at least 4 or larger, or ¼.sup.th or smaller, the apparatus comprising: a receiver (206) arranged to receive a luminance mapping function (F_L_s2h) defining a mapping between the luminance of the input color (Y′L) and a reference luminance (L′_HDR), and an initial saturation processing function (F_sat) defining saturation boost values (b) for different values of the luminance of the input color (Y′L); a display tuning unit (1009) arranged to calculate a display tuned luminance mapping function (F_L_da) based on the luminance mapping function (F_L_s2h) and at least one of a display peak brightness (PB_D) and a minimum discernable black (MB_D); a luminance processor (401) arranged to apply the display tuned luminance mapping function (F_L_da) to determine an output luminance (Y′M) from the input luminance (Y′L) of the input color; and a saturation processing unit (410, 411), arranged to map the input color saturation (C′bL, C′rL) to the color saturation (Cb′M, Cr′M) of the output color on the basis of a saturation processing strategy which specifies saturation multipliers for the normalized luminance values (Y_norm); characterized in that the apparatus further comprises a saturation factor determination unit (402) arranged to calculate a final saturation processing strategy (b; Bcorr) based on the initial saturation processing strategy (F_sat) and based on a secondary luminance value (Y′_H) which is derivable from the output luminance (Y′M) by applying a luminance mapping function (F_M2H) based on the luminance mapping function (F_L_s2h), and whe