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 method of data encoding input data values of a data set for encoding includes selecting one of a plurality of complementary sub-ranges of a set of code values according to the value of a current input data value, the set of code values being defined by a range variable, assigning the current input data value to a code value within the selected sub-range, modifying the set of code values in dependence upon the assigned code value and the size of the selected sub-range, detecting whether the range variable defining the set of code values is less than a predetermined minimum size and if so, successively increasing the range variable so as to increase the size of the set of code values until it has at least the predetermined minimum size and outputting an encoded data bit in response to each such size-increasing operation, and 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 value in the subset having

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 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 method of data encoding input data values of a data set for encoding includes selecting one of a plurality of complementary sub-ranges of a set of code values according to the value of a current input data value, the set of code values being defined by a range variable, assigning the current input data value to a code value within the selected sub-range, modifying the set of code values in dependence upon the assigned code value and the size of the selected sub-range, detecting whether the range variable defining the set of code values is less than a predetermined minimum size and if so, successively increasing the range variable so as to increase the size of the set of code values until it has at least the predetermined minimum size and outputting an encoded data bit in response to each such size-increasing operation, and 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 value in the subset having

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 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 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 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 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 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 using inter-image prediction to encode input video data in which each chrominance component has 1/Mth of the horizontal resolution and 1/Nth of the vertical resolution of the luminance component, where M and N are integers equal to 1 or more, including 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 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, 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.

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 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 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: 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 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 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 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 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.