Abstract: An image encoding apparatus comprises a selector configured to select, from a set of candidate prediction operations each defining at least a prediction direction, a prediction operation for prediction of samples of a current region of a current image, the current region comprising an array of two or more rows and two or more columns of samples; an intra-image predictor configured to derive predicted samples of the current region with respect to one or more of a group of reference samples of the same image in dependence upon a prediction direction, defined by the selected prediction operation, between a current sample to be predicted and a reference position amongst the reference samples; in which, for at least some of the candidate prediction operations, the group of reference samples comprises two or more parallel linear arrays of reference samples disposed at different respective separations from the current region; a detector configured to detect whether samples corresponding to any of the two or more par

Abstract: Apparatus comprises a data encoder configured to derive, from an array of sample values, sample range flags each indicative of whether one or more sample values of the array of sample values lie in a predetermined range of sample values, the data encoder being configured in a first encoding mode to encode the array of sample values, at least in part, by encoding the sample range flags to an output data stream; a predictor configured to predict the state of a group of the sample range flags for a given array of sample values, the group being at least a subset of the sample range flags; and a comparator configured to compare the predicted state of the group of sample range flags with the actual state of the respective sample range flags for the given array of sample values; the data encoder being configured, in response to the comparator, to encode the given array of samples values in a second encoding mode in which the encoder is configured to encode to the output data stream a predetermined number of indicato

Abstract: A data encoding method comprises: encoding an ordered array of data values as data representing a data value magnitude and data representing a data value sign; predicting, for a set of data values comprising at least some of the data values, the respective data value sign from a property of one or more other data values in the ordered array; and encoding the data value sign for the set of data values in dependence upon the respective predicted value.

Abstract: Apparatus comprises video data decoder circuitry configured to decode an input video data stream, the video data decoder being responsive to parameter data associated with the input video data stream, the parameter data indicating a profile selected from a plurality of profiles, each profile defining a decoding attribute comprising one or more of a bit depth and a chrominance subsampling format; detector circuitry configured to detect constraint data associated with the input video data stream, the constraint data defining a difference between a decoding attribute applicable to the input video data stream and the decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the decoding attribute by a zero value of the constraint data; and control circuitry configured to control the video data decoder to decode the input video data stream to generate a decoded video data stream having a decoding attribute defined by the e

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: Apparatus comprises video data decoder circuitry configured to decode an input video data stream, the video data decoder being responsive to parameter data associated with the input video data stream, the parameter data indicating a profile selected from a plurality of profiles, each profile defining a decoding attribute comprising one or more of a bit depth and a chrominance subsampling format; detector circuitry configured to detect constraint data associated with the input video data stream, the constraint data defining a difference between a decoding attribute applicable to the input video data stream and the decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the decoding attribute by a zero value of the constraint data; and control circuitry configured to control the video data decoder to decode the input video data stream to generate a decoded video data stream having a decoding attribute defined by the e

Abstract: A method of encoding successive data items comprises storing history data for encoded data items, the history data indicating one or more aspects of encoding the encoded data items; encoding a given data item by a first encoding technique comprising encoding a series of zero or more data sets, each data set representing a respective range of values of the data items and selecting the series of data sets from a plurality of candidate data sets in dependence upon (i) a number of previously encoded data sets; and (ii) the history data applicable to a given property of the given data item; and encoding any remaining value of the given data item, the remaining value being an amount by which the given data item exceeds a maximum value which can be encoded by the first encoding technique, by a second encoding technique different to the first encoding technique.

Abstract: An image encoding apparatus comprises a controller configured to select, from a set of prediction directions, a set of candidate prediction directions as a subset of the set of prediction directions, for a current image region of a current image in dependence upon one or more properties of a group of reference samples of the current image applicable to the current image region; and an intra-image predictor configured to predict samples of the current image region with respect to one or more of the group of reference samples of the same image according to a prediction direction between the current sample and a reference position amongst the reference samples; in which the intra-image predictor is configured to select the prediction direction for the current image region from the set of candidate prediction directions.

Abstract: Apparatus comprises a video data decoder; and a coded picture buffer to buffer successive portions of an input video data and provide a portion to the video data decoder for decoding, the coded picture buffer having a coded picture buffer size; the video data decoder being responsive to parameter data associated with the input video data, the parameter data indicating, for a given input video data, an encoding level selected from a plurality of encoding levels, each level defining at least a maximum luminance picture size, a minimum compression ratio and a maximum value of the coded picture buffer size; in which for each encoding level of the plurality of encoding levels, the maximum value of the coded picture buffer size is greater than or equal to the number of bits required to represent a picture at the maximum luminance picture size when encoded according to the minimum compression ratio.

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: An image encoding apparatus comprises a selector configured to select, from a set of candidate prediction operations each defining at least a prediction direction, a prediction operation for prediction of samples of a current region of a current image, the current region comprising an array of two or more rows and two or more columns of samples; an intra-image predictor configured to derive predicted samples of the current region with respect to one or more of a group of reference samples of the same image in dependence upon a prediction direction, defined by the selected prediction operation, between a current sample to be predicted and a reference position amongst the reference samples; in which, for at least some of the candidate prediction operations, the group of reference samples comprises two or more parallel linear arrays of reference samples disposed at different respective separations from the current region; a detector configured to detect whether samples corresponding to any of the two or more par

Abstract: A video data encoding method for encoding an array of video data values comprises the steps of: 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 of fourteen bits, the frequency transform being a discrete cosine transform; defining a 64×64 transform matrix M64 for a 64×64 DCT transform, the matrix M64 being defined by the accompanying FIGS. 10a-10e and 11; for an N×N transform where N is 2, 4, 8 or 16, subsampling the 64×64 transform matrix M64 to select a subset of N×N values, the subset MN[x][y] of values being defined by: MN[x][y]=M64[x][(2(6-log2(N)))y] for x,y=0 . . . (N?1).

Abstract: An apparatus including a video data decoder configured to decode an input video data stream, the video data decoder being responsive to a parameter value associated with the input video data stream, the parameter value indicating an encoding level selected from a plurality of encoding levels, each encoding level defining at least a maximum luminance picture size and a maximum luminance sample rate, the encoding level defining a first numerical component and a second numerical component, the second numerical component being a numerical value greater than or equal to zero, in which for encoding levels having a second numerical component of zero, the first numerical component increases monotonically with increasing maximum luminance picture size, and the second component varies with the maximum luminance sample rate; the parameter value being a numeric encoding of the encoding level.

Abstract: An image encoding apparatus comprises a selector configured to select, from a set of candidate prediction operations each defining at least a prediction direction selected from a set of available prediction directions, a prediction operation for prediction of samples of a current region of a current image, the current region comprising an array of two or more rows and two or more columns of samples; and an intra-image predictor configured to derive predicted samples of the current region with respect to one or more of a group of reference samples of the same image in dependence upon a prediction direction, defined by the selected prediction operation, between a current sample to be predicted and the reference samples; in which for at least some of the candidate prediction operations: the group of reference samples comprises two or more parallel linear arrays of reference samples disposed at different respective separations from the current region, the intra-image predictor being configured to derive the predi

Abstract: A method of encoding video data values, the method including selectively encoding, via circuitry, a high bit depth control flag and, when the high bit depth control flag is set to indicate high bit depth operation, selectively encoding an extended precision flag to indicate at least extended precision operation of a spatial frequency transform stage and encoding the video data values according to a mode of operation defined by the encoded high bit depth control flag and, when encoded, the extended precision flag.

Abstract: An image encoding apparatus comprises a selector configured to select a prediction operation, for prediction of samples of a current region of a current image with respect to one or more of a group of reference samples, from a set of candidate prediction operations, at least some of which define, as an intra-image prediction operation, a prediction direction between a current sample to be predicted and a group of reference samples in the same image; and an intra-image predictor configured to derive predicted samples of a current image region from reference samples of the same image in response to selection, by the selector, of an intra-image prediction operation for the current image region; in which: the current region comprises at least a subset of a current coding tree unit (CTU) in an array of CTUs; the group of references samples is disposed, with respect to the current image region at one or more predetermined sides of the current image region; and the selector is configured to inhibit the selection of

Abstract: Image data encoding apparatus, comprises an entropy encoder configured to selectively encode data items representing image data so as to generate encoded binarized symbols of successive output data units; the entropy encoder being configured to generate an output data stream subject to a constraint defining an upper limit to the number of binarized symbols that may be expressed by any individual output data unit relative to the size in bytes of that output data unit, in which the entropy encoder is configured to provide padding data, for each output data unit which does not meet the constraint, so as to increase the size in bytes of that output data unit in order to meet the constraint; the apparatus comprising: an attribute detector configured to detect an encoding attribute applicable to a given output data unit; and a selector configured to select, in response to the detected encoding attribute, a constraint, for use with the given output data unit, from two or more candidate constraints.

Abstract: An image encoding apparatus comprises a selector configured to select, from a set of candidate prediction operations each defining at least a prediction direction selected from a set of available prediction directions, a prediction operation for prediction of samples of a current region of a current image, the current region comprising an array of two or more rows and two or more columns of samples; and an intra-image predictor configured to derive predicted samples of the current region with respect to one or more of a group of reference samples of the same image in dependence upon a prediction direction, defined by the selected prediction operation, between a current sample to be predicted and the reference samples; in which for at least some of the candidate prediction operations: the group of reference samples comprises two or more parallel linear arrays of reference samples disposed at different respective separations from the current region, the intra-image predictor being configured to derive the predi

Abstract: Image data encoding apparatus comprises an entropy encoder for selectively encoding data items representing image data to be encoded by a first, context adaptive binary arithmetic coding (CABAC), encoding system or by a second, bypass, encoding system, so as to generate encoded binarized symbols; the image data representing one or more pictures of a picture sequence, each picture comprising two or more output data units representing respective sub-sections of the picture, each sub-section being decodable and reconstructable independently of other sub-sections in that picture and picture sequence; the entropy encoder being configured to generate an output data stream subject to a constraint defining an upper limit to the number of binarized symbols that may be expressed by any individual output data unit relative to the size in bytes of that output data unit, in which the entropy encoder is configured to apply the constraint to each output data unit, and to provide padding data, for each output data unit which

Abstract: Image data encoding apparatus comprises an entropy encoder for selectively encoding data items representing image data to be encoded by a first, context adaptive binary arithmetic coding (CABAC), encoding system or by a second, bypass, encoding system, so as to generate encoded binarized symbols; the image data representing one or more pictures of a picture sequence, each picture comprising two or more output data units representing respective sub-sections of the picture, each sub-section being decodable and reconstructable independently of other sub-sections in that picture and picture sequence; in which each sub-section is subject to a respective minimum compression ratio.