Abstract: A method encoding image data including: encoding the image data by an inter-image predictor in which a block of one or more samples of a current image is predicted from a reference block of samples located at one of a number of candidate block positions in a reference image; and selectively applying a constrained inter-image prediction mode in which, in comparison to an inter-image prediction mode for the encoding, one or both of the number of candidate block positions and the number of candidate reference images is reduced.

Abstract: A video data decoding apparatus is configured to detect a control flag associated with at least a part of an encoded image for decoding, in which in a lossless mode of operation, a first control flag state enables sample-based angular intra-prediction but disables edge filtering of prediction samples, and a second control flag state disables sample-based angular intra prediction but enables edge filtering of prediction samples; and in a lossy mode of operation, the first control flag state enables residual differential pulse code modulation coding and enables edge filtering of prediction samples, and the second control flag state disables residual differential pulse code modulation coding but enables edge filtering of prediction samples.

Abstract: A method encoding successive input data values includes: selecting one of plural complementary sub-ranges of a set of code values according to a current input data value, proportions of the sub-ranges relative to the set of code values defined by a context variable associated with that input data value; assigning the current input data value to a code value within the selected sub-range; modifying the set of code values based on the assigned code value and a size of the selected sub-range; detecting whether the set of code values is less than a predetermined minimum size and if so, successively increasing it until reaching the predetermined minimum size; outputting an encoded data bit in response to each size-increasing operation; modifying the context variable to increase the proportion of the set of code values in the sub-range selected; after encoding a group of input data values, terminating the output data.

Abstract: A method decoding a data values set includes: decoding a first portion of each data value from one or more data sets; decoding a second portion depending on integer bits of data values not fully encoded by the data sets, and, if a data value has not been fully decoded by first and second portions, decoding a remaining third portion of the data value; detecting, for a subset of the data values, (i) instances of data values for which a third portion has been encoded and would still have been required had a higher value of n been used, and (ii) instances of data values for which a second portion has been encoded but the value of n was such that the data value could have been fully encoded by first and second portions using a lower value of n; and varying n for use in subsequent data values.

Abstract: A video data decoding apparatus is configured to detect a control flag associated with at least a part of an encoded image for decoding, in which in a lossless mode of operation, a first control flag state enables sample-based angular intra-prediction but disables edge filtering of prediction samples, and a second control flag state disables sample-based angular intra prediction but enables edge filtering of prediction samples; and in a lossy mode of operation, the first control flag state enables residual differential pulse code modulation coding and enables edge filtering of prediction samples, and the second control flag state disables residual differential pulse code modulation coding but enables edge filtering of prediction samples.

Abstract: A method of encoding image data, including: frequency-transforming input image data to generate an array of frequency-transformed input image coefficients by a matrix-multiplication process, according to a maximum dynamic range of the transformed data and using transform matrices having a data precision; and selecting the maximum dynamic range and/or the data precision of the transform matrices according to the bit depth of the input image data.

Abstract: A data encoding method includes encoding an array of data values as data sets and escape codes for values not encoded by the data sets, an escape code including a prefix portion and a non-unary coded suffix portion having a length, in bits, dependent upon a value encoded by the prefix portion according to a relationship such that, for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the length, in bits, of the prefix portion.

Abstract: A method encoding data values of a data set, including: selecting one of plural complementary sub-ranges of a code values set according to a current input data value, the code values set defined by a range variable; assigning the current input data value to a code value within the selected sub-range; modifying the code values set depending on the assigned code value and size of the selected sub-range; detecting whether the range variable is less than a predetermined minimum size and if so, successively increasing the range variable to increase the code values set size to at least the predetermined minimum size; outputting an encoded data bit in response to each size-increasing operation; after encoding a group of input data values, setting the range variable to a value selected from a predetermined subset of available range variable values, each subset value having at least one least significant bit of zero.

Abstract: A video data encoding apparatus operable to encode an array of input video data values includes: a differential pulse code modulation (DPCM) coder configured to apply a differential pulse code modulation operation to the array of input video data values to generate an array of DPCM data values; a quantizer operable to quantize data derived from the DPCM data values; and controller circuitry controlling selection of a rounding operation by the quantizer from two or more candidate rounding operations.

Abstract: A video data decoding apparatus in which if a detector detects a transform-skip mode is not applicable to an array of encoded video data values, the detector controls a dequantizer to apply dequantization parameters which may vary between data values in the array of encoded data values according to a position of each data value within the array, and controls an inverse frequency transformer to apply an inverse frequency transform to the dequantized data values; and if the detector detects the transform-skip mode is applicable to the array of encoded video data values, the detector controls the dequantizer to apply dequantization parameters which, for each array of encoded data values, are independent of the position of each data value within the array, and controls the inverse frequency transformer not to apply an inverse frequency transform to the dequantized data values.

Abstract: The present disclosure relates to an image processing device and a method that enable easier encoding and decoding of a wider variety of images. The image processing device includes: a setting unit that sets a parameter indicating a setting state of a coding tool required in specifying an extended profile that is an extension of a profile specified in a coding standard for performing encoding on each unit having a recursive hierarchical structure; and an encoding unit that generates an encoded stream by encoding an image in accordance with the parameter set by the setting unit. The present disclosure can be applied to image processing devices that encode image data, for example.

Abstract: A video data encoding method for encoding an array of video data values includes frequency-transforming the video data values according to a frequency transform, to generate an array of frequency-transformed values by a matrix-multiplication process using a transform matrix having a data precision greater than six bits.

Abstract: A data encoding method for encoding an array of data values as data sets and escape codes for values not encoded by the data sets, an escape code including a unary coded portion and a non-unary coded portion, the method including: setting a coding parameter defining a minimum number of bits of a non-unary coded portion; adding an offset value of 1 or more to the coding parameter to define a minimum least significant data portion size; generating one or more data sets indicative of positions, relative to the array of data values, of data values of predetermined magnitude ranges, to encode the value of at least one least significant bit of each data value; generating respective complementary most-significant data portions and least-significant data portions; encoding the data sets; encoding the most significant data portions; and encoding the least-significant portions.

Abstract: A video data decoding apparatus is configured to detect a control flag associated with at least a part of an encoded image for decoding, in which in a lossless mode of operation, a first control flag state enables sample-based angular intra-prediction but disables edge filtering of prediction samples, and a second control flag state disables sample-based angular intra prediction but enables edge filtering of prediction samples; and in a lossy mode of operation, the first control flag state enables residual differential pulse code modulation coding and enables edge filtering of prediction samples, and the second control flag state disables residual differential pulse code modulation coding but enables edge filtering of prediction samples.

Abstract: A method of coding 4:2:2 or 4:4:4 video data comprises predicting luminance and/or chrominance samples of an image from other respective reference samples derived from the same image according to a prediction mode associated with a sample to be predicted, the prediction mode being selected for each of a plurality of blocks of samples, from a set of two or more candidate prediction modes; detecting differences between the samples and the respective predicted samples; selecting a frequency-separation transform from two or more candidate frequency separation transforms according to the prediction mode associated with a current block of samples using a mapping between transform and prediction mode, the mapping between different, as between chrominance and luminance samples, for at least the 4:4:4: format; and encoding the detected differences by frequency-separating the differences, using the selected frequency-separation transform.

Abstract: A video coding or decoding method in which luminance and chrominance samples in a 4:4:4 format or a 4:2:2 format are predicted from other respective samples according to a prediction direction associated with blocks of samples to be predicted; comprises detecting a prediction direction in respect of a current block to be predicted; generating a predicted block of chrominance samples according to other chrominance samples defined by the prediction direction; if the detected prediction direction is substantially vertical, filtering the left column of samples in the predicted block of chrominance samples, or if the detected prediction direction is substantially horizontal, filtering the top row of samples in the predicted block of chrominance samples; and encoding a difference between the filtered predicted chrominance block and the actual chrominance block or applying a decoded difference to the filtered predicted chrominance block so as to encode or decode the block respectively.

Abstract: A video coding or decoding method operable to generate blocks of quantized spatial frequency data by quantizing the video data according to a selected quantization step size and a matrix of data modifying the quantization step size for use at different respective block positions within an ordered block of samples, the method being operable with respect to at least two different chrominance subsampling formats, and includes for at least one of the chrominance subsampling formats, defining one or more quantization matrices as one or more predetermined modifications with respect to one or more reference quantization matrices defined for a reference one of the chrominance subsampling formats.

Abstract: 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.

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

Abstract: A video coding or decoding method using inter-image prediction to encode input video data in which each chrominance component has 1/Mth of the horizontal resolution of the luminance component and 1/Nth of the vertical resolution of the luminance component, where M and N are integers equal to 1 or more, comprises: storing one or more images preceding a current image; interpolating a higher resolution version of prediction units of the stored images so that the luminance component of an interpolated prediction unit has a horizontal resolution P times that of the corresponding portion of the stored image and a vertical resolution Q times that of the corresponding portion of the stored image, where P and Q are integers greater than 1; detecting inter-image motion between a current image and the one or more interpolated stored images so as to generate motion vectors between a prediction unit of the current image and areas of the one or more preceding images; and generating a motion compensated prediction of the pr