Abstract: A method of encoding a coding tree unit in a video bitstream. A plurality of candidate configurations are formed for the coding tree unit, each of the candidate configurations having a variation of at least one of a set of partitioning modes and encoding parameters. A candidate configuration is selected from the plurality of candidate configurations based on a predetermined maximum bit rate for the coding tree unit, the selected candidate configuration having a size within the predetermined maximum bit rate. The coding tree unit is encoded using the selected candidate configuration.

Abstract: Disclosed is method of decoding, from a video bitstream, a transform unit containing at least one chroma residual coefficient array associated with a single chroma channel. The method determines a size of the transform unit related to a hierarchical level of the transform unit in a corresponding coding unit, and identifies a maximum number of inverse transforms according to the determined size. The method decodes from the video bitstream the at least one chroma residual coefficient array using the identified maximum number of transforms, selects an inverse transform for the decoded chroma residual coefficient arrays, the inverse transform being selected from a predetermined set of inverse transforms, and applies the selected inverse transform to each of the chroma residual coefficient arrays to decode chroma residual samples for the chroma channel of the transform unit. A similar encoding method is also disclosed.

Abstract: A method of determining luma values from 4:4:4 RGB video data for encoding chroma downsampled 4:2:0 YCbCr video data into a bitstream. Initial coefficents are determined for a region of a colour space the region being one of a plurality of regions located in the colour space and each region having a plurality of associated coefficients. The determined initial coefficients are applied to an initial image to produce a test image, the test image being a chroma downsampled 4:2:0 YCbCr version of the initial image. A measure of quality is determined by comparing the initial image and the test image. The determined initial coefficients are modified to increase the determined measure of quality. Luma values are determined from 4:4:4 RGB video data for encoding chroma downsampled 4:2:0 YCbCr video data into a bitstream using the modified coefficients.

Abstract: A method of decoding a bit-stream of encoded video data in a video decoder is disclosed. The method determines if the bit-stream of encoded video data has extended precision processing enabled and has a bit-depth greater than nine bits, when a profile of the bit-stream of the encoded video data is determined to be unsupported by the video decoder. The bit-stream of the encoded video data is decoded to determine decoded video data, using a profile supported by the video decoder, if the bit stream has extended precision processing enabled and a bit depth greater than nine (9) bits. The decoded video data has differences to the video data encoded in the bit-stream due to the unsupported profile being different to the supported profile.

Abstract: A method of determining a luma value from 4:4:4 RGB video data for encoding chroma downsampled 4:2:0 YCbCr video data into a bitstream. A location, in a colour space defined by linear luminance and non-linear 4:2:0 chroma values, is determined from the RGB video data. A region that contains the determined location is determined, the region being one region of a plurality of regions located in the colour space and having a plurality of associated coefficients. One or more of the coefficients associated with the determined region are selected, the selected coefficients being used to map the linear luminance and non-linear 4:2:0 chroma values to a luma value that compensates for a luminance shift introduced by chroma downsampling of the non-linear 4:2:0 chroma values. The method then determines the luma value for encoding into the bitstream according to a function of the selected coefficients and the determined location.

Abstract: A method of encoding a portion of a video frame into a video bitstream, in which the portion of the video frame contains samples, take account the samples representing luminance levels according to an EOTF. The method determines a luminance of the portion of the video frame, and a desired (environment) luminance step size. The desired luminance step size represents a just noticeable difference (JND) determined according to the determined luminance and a predetermined ambient luminance, the desired luminance step size being greater than a luminance (transfer function) step size from the EOTF. The method then determines a quantisation parameter from the desired luminance step size and the luminance step size from the EOTF, the quantisation parameter being used for encoding the portion of the video frame, and then encodes encoding the portion of the video frame into the video bitstream according to the determined quantisation parameter.

Abstract: A method of de-blocking an edge of a block of samples of video data is disclosed. A first prediction mode is decoded for a first block of two adjacent blocks of video data, each of the blocks of video data including a primary colour channel and at least one secondary colour channel. A second prediction mode is decoded for a second block of the two adjacent blocks of video data. A boundary strength value is determined for a block of samples along an edge corresponding to a boundary between said first block of video data and said second block of video data. A weak de-blocking filter is applied to the block of data along said edge if the determined boundary strength value indicates that the first prediction mode is intra prediction and the second prediction mode is intra-block copy prediction. The weak de-blocking filter is different to a filter applied to a block determined to have two, adjacently located, intra prediction mode blocks.

Abstract: A plurality of display device profiles is decoded from a bitstream containing video data. A display device profile is selected by comparing at least a portion of the device information of the display device profiles with corresponding device information of the first display device. An image modification parameter set is selected from a plurality of image modification parameter sets according to the selected display device profile, the plurality of image modification parameter sets being decoded from the bitstream and each of the plurality of image modification parameter sets providing information regarding luminance mapping to be applied to one or more portions of the video data. At least a portion of the video data is displayed on the first display device from the bitstream of video data by applying the selected image modification parameter set to the portion of video data from the bitstream of video data.

Abstract: A method of displaying images on a display. Images from a video playback are displayed on the display with a first luminance profile, the luminance profile mapping video data samples to output luminance of the display. A user initiated modification of a speed of the video playback is detected. A second luminance profile is determined for the display of the video playback, the second luminance profile being determined according to the modified speed of the video playback and a predetermined adaptation speed of a human visual system of a viewer of the video playback. Further images from the video playback are displayed on the display using the determined second luminance profile.

Abstract: A method of decoding a current block encoded using intra-prediction includes determining prediction modes for coding blocks neighbouring the current block. The method generates prediction values for edge samples of the decoded block from intra-prediction reference samples of the neighbouring coding blocks by applying an intra-prediction process to the intra-prediction encoded current block if a number of the neighbouring coding blocks determined to one of use intra-block copy prediction mode and palette mode is greater than or equal to a predetermined threshold. Alternatively the method generates the prediction values for the edge samples of the decoded block from intra-prediction reference samples of the neighbouring coding blocks by applying a filter, preferably an intra-boundary filter, to reference samples of the neighbouring blocks. The current block is then decoded based on the prediction values.

Abstract: A method of generating intra-predicted samples for a chroma channel of a video bitstream configured for a 4:2:2 chroma format. An intra-prediction angle is determined from an intra-prediction mode for the chroma channel, the intra-prediction mode being one of a plurality of horizontal intra-prediction modes. The intra-prediction angle due to the 4:2:2 chroma format is adjusted. A change threshold between the horizontal intra-prediction modes and vertical intra-prediction modes is modified if the adjusted angle exceeds a predetermined value, the modified change threshold being configured for converting the adjusted intra-prediction angle from one of the plurality of horizontal intra-prediction modes to a vertical intra-prediction mode. Intra-predicted samples are generated using a vertical intra-prediction mode according to the adjusted intra-prediction angle, and the change threshold.

Abstract: Disclosed is a method of decoding (712, 715, 718) sample adaptive offset type index data (242, sao_type_idx) from a received stream of encoded video data (113). The method determines an arithmetically encoded first portion (501;591) of a sample adaptive offset type index value (500, 590) from the stream of video data, and a bypass encoded second portion (502; 592) of the sample adaptive offset type index value when the first portion indicates that the second portion will be present in the stream of video data. The method decodes (7100, 7700, 7800; 7300, 7940, 7960) the sample adaptive offset type index from a combination of the decoded first and second portions of the sample adaptive offset type index values. The sample adaptive offset type index data is used to select one of a plurality of offsets in digital video decoding. Corresponding methods of encoding are also disclosed.

Abstract: A method of copying a block of samples of a video bitstream, is disclosed. A plurality of adaptation parameters is read from a local memory store. Each adaptation parameter corresponds to a component of a multi-dimensional vector in the video bitstream. Each of the components of the vector is decoded from the video bitstream using the corresponding adaptation parameter. The block of samples is copied from the video bitstream. The spatial location of the block of samples is identified using the decoded components of the vector.

Abstract: A method of decoding a coding unit from a video bitstream determines reconstructed samples for a first coding unit, from the video bitstream, and decodes a dictionary store flag from the video bitstream for the first coding unit. Where the dictionary store flag indicates that reconstructed samples for the first coding unit be stored, the method (i) stores the reconstructed samples for the first coding unit into a memory buffer; (ii) determines reconstructed samples for a second coding unit, the reconstructed samples for the second coding unit being copied from reconstructed samples for the first coding unit from the memory buffer, and (iii) outputs the reconstructed samples for the second coding unit. Also disclosed is a complementary method for encoding, a decoder and an encoder.

Abstract: Disclosed is method of decoding, from a video bitstream, a transform unit containing at least one chroma residual coefficient array associated with a single chroma channel. The method determines a size of the transform unit related to a hierarchical level of the transform unit in a corresponding coding unit, and identifies a maximum number of inverse transforms according to the determined size. The method decodes from the video bitstream the at least one chroma residual coefficient array using the identified maximum number of transforms, selects an inverse transform for the decoded chroma residual coefficient arrays, the inverse transform being selected from a predetermined set of inverse transforms, and applies the selected inverse transform to each of the chroma residual coefficient arrays to decode chroma residual samples for the chroma channel of the transform unit. A similar encoding method is also disclosed.

Abstract: A method of decoding a transform unit (e.g., 400) of encoded video data using Golomb-Rice decoding is disclosed. Significant residual coefficients for a sub-set of the transform unit are determined A predetermined Rice parameter for Golomb-Rice decoding of the subset of the transform unit is selected. The predetermined Rice parameter being offset from a zero setting when the determined number of significant residual coefficients is higher than a predetermined threshold. The subset of the transform unit is decoded using the predetermined Rice parameter as an initial parameter for the Golomb-Rice decoding.

Abstract: A method of decoding a bit-stream of encoded video data in a video decoder is disclosed. The method determines if the bit-stream of encoded video data has extended precision processing enabled and has a bit-depth greater than nine bits, when a profile of the bit-stream of the encoded video data is determined to be unsupported by the video decoder. The bit-stream of the encoded video data is decoded to determine decoded video data, using a profile supported by the video decoder, if the bit stream has extended precision processing enabled and a bit depth greater than nine (9) bits. The decoded video data has differences to the video data encoded in the bit-stream due to the unsupported profile being different to the supported profile.