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: An apparatus includes: an image encoder to encode an image as a plurality of image regions, the image encoder selecting at least one of the size and the shape of each image region; and an intra-image predictor to predict a current sample of a current region of an image with respect to one or more 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 prediction direction is selected from a set of candidate prediction directions; the intra-image predictor being configured to apply two or more different sets of candidate prediction directions in dependence upon an aspect of the image region, the aspect being one of more of: the region shape and the position of the region within the image. Optionally the aspect further includes the region size.

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.

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: 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: 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: An image decoding 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; 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 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.

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 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 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 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 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: An image data encoding and/or decoding apparatus comprises a data processor to process an image data signal comprising successive arrays of data values according to respective data value processing orders associated with the arrays of data values; and a processing order selector to select a processing order for processing a current array of data values in dependence on one or more attributes of a plurality of arrays of data values in the image data signal already processed by the data processor.

Abstract: A video encoding method for encoding both the 4:2:0 video and 4:4:4 video formats. The method includes generating blocks of quantized spatial frequency data by quantizing coefficients and generating a matrix of data. The method further includes determining quantization matrices for use with at least two block sizes. The method further includes determining a first quantization matrix for a 32×32 chroma block of samples with respect to a first modification of a first scaling list for quantization of a block of samples smaller than 32×32, and determining, for blocks of another block size different than the 32×32 chroma block of samples, a second quantization matrix by modifying a second scaling list according to a second modification. The second scaling list is different from the first scaling list, and the first scaling list is a reference scaling list for video in 4:2:0 video format.

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: An apparatus includes: an image encoder to encode an image as a plurality of image regions, the image encoder selecting at least one of the size and the shape of each image region; and an intra-image predictor to predict a current sample of a current region of an image with respect to one or more 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 prediction direction is selected from a set of candidate prediction directions; the intra-image predictor being configured to apply two or more different sets of candidate prediction directions in dependence upon an aspect of the image region, the aspect being one of more of: the region shape and the position of the region within the image. Optionally the aspect further includes the region size.

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 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 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.