The disclosure relates to an image processing apparatus for compressing or decompressing a segment of an image, the segment being non-rectangular and comprising a plurality of pixels, each pixel comprising a pixel value, the pixel values of the plurality of pixels forming a pixel value vector, the apparatus comprising: a processor configured to compress the segment or configured to decompress the segment, wherein compressing the segment comprises computing a plurality of expansion coefficients by expanding the pixel value vector into a plurality of basis vectors, wherein the basis vectors are discrete approximations of solutions of a boundary value problem of the Helmholtz equation on the segment of the image; and wherein decompressing the segment comprises computing the pixel value vector by forming a linear combination of the basis vectors according to the plurality of expansion coefficients.

A method for encoding a raw lenselet image includes a receiving phase, wherein at least a portion of a raw lenselet image is received, the image including a plurality of macro-pixels, each macro-pixel having pixels corresponding to a specific view angle for the same point of a scene, and an output phase, wherein a bitstream having at least a portion of an encoded lenselet image is outputted. The method has an image transform phase, wherein the pixels of said raw lenselet image are spatially displaced in a transformed multi-color image having a larger number of columns and rows with respect to the received raw lenselet image, wherein dummy pixels having undefined value are inserted into the raw lenselet image and wherein the displacement is performed so as to put the estimated center location of each macro-pixel onto integer pixel locations. Moreover, the method includes a sub-view generation phase, wherein a sequence of sub-views is generated, said sub-views having pixels of the same angular coordinates extracted from different macro-pixels of the transformed raw lenselet image. Finally, the method has a graph coding phase, wherein a bitstream is generated by encoding a graph representation of at least one of the sub-views of the sequence according to a predefined graph signal processing technique.

An example method includes determining a color component of a unit of video data; determining, based at least on the color component, a context for context-adaptive binary arithmetic coding (CABAC) a syntax element that specifies a value of a low-frequency non-separable transform (LFNST) index for the unit of video data; CABAC decoding, based on the determined context and via a syntax structure for the unit of video data, the syntax element that specifies the value of the LFNST index for the unit of video data; and inverse-transforming, based on a transform indicated by the value of the LFNST index, transform coefficients of the unit of video data.

A video coding or decoding method in which luminance and chrominance samples are predicted from other respective reference samples according to a prediction direction associated with a current sample to be predicted, the chrominance samples having a lower horizontal and/or vertical sampling rate than the luminance samples so that the ratio of luminance horizontal resolution to chrominance horizontal resolution is different than the ratio of luminance vertical resolution to chrominance vertical resolution, so that a block of luminance samples has a different aspect ratio to a corresponding block of chrominance samples, the method including: detecting a first prediction direction defined in relation to a first grid of a first aspect ratio in respect of a set of current samples to be predicted; and applying a direction mapping to the prediction direction to generate a second prediction direction defined in relation to a second grid of a different aspect ratio.

A set of software applications configured to perform interframe and/or intraframe encoding operations based on data communicated between a graphics application and a graphics processor. The graphics application transmits a 3D model to the graphics processor to be rendered into a 2D frame of video data. The graphics application also transmits graphics commands to the graphics processor indicating specific transformations to be applied to the 3D model as well as textures that should be mapped onto portions of the 3D model. Based on these transformations, an interframe module can determine blocks of pixels that repeat across sequential frames. Based on the mapped textures, an intraframe module can determine blocks of pixels that repeat within an individual frame. A codec encodes the frames of video data into compressed form based on blocks of pixels that repeat across frames or within frames.

A method of video coding in respect of a 4:2:2 chroma subsampling format includes dividing image data into transform units. In a case of a non-square transform unit, the method includes splitting the non-square transform unit into square blocks prior to applying a spatial frequency transform. The method further includes applying a spatial frequency transform to the square blocks to generate corresponding sets of spatial frequency coefficients.

Systems, methods, and instrumentalities are disclosed relating to intra prediction of a video signal based on mode-dependent subsampling. A block of coefficients associated with a first sub block of a video block, one or more blocks of coefficients associated with one or more remaining sub blocks of the video block, and an indication of a prediction mode for the video block may be received. One or more interpolating techniques, a predicted first sub block, and the predicted sub blocks of the one or more remaining sub blocks may be determined. A reconstructed first sub block and one or more reconstructed remaining sub blocks may be generated. A reconstructed video block may be formed based on the prediction mode, the reconstructed first sub block, and the one or more reconstructed remaining sub blocks.

An image encoding and decoding method, includes: determining location information of a target reconstructed image block of a current to-be-encoded image block, where the target reconstructed image block is a reconstructed image block used to determine motion information of the current to-be-encoded image block; determining a first transform core pair based on the location information of the target reconstructed image block; and transforming a residual signal of the current to-be-encoded image block based on the first transform core pair, to obtain a transform coefficient.

A method of point cloud coding using homography transform sends the homography transform of the 3D patches, instead of the explicit projection values (such as bounding boxes and patch orientation, rotation). The method has a more compact notation, is more efficient in terms of transmission, and allows for a faster decoding, particularly in cases where the 3D points will be reprojected.

Disclosed herein is a method for performing decoding using a Layered Givens Transform (LGT), which includes: deriving a plurality of rotation layers and at least one permutation layer, wherein the rotation layer includes a permutation matrix and a rotation matrix, and the rotation matrix includes at least one pairwise rotation matrix; acquiring an LGT coefficient using the plurality of rotation layers and the at least one permutation layer; and performing inverse transform using the LGT coefficient, in which the rotation layer may be derived based on edge information indicating a pair to which the at least one pairwise rotation matrix is applied.