Abstract: The present invention is related to video coding and decoding, in particular HEVC RExt that define a palette coding mode dedicated to the coding of screen contents. In improved palette coding modes according to the invention, when building a palette, each time a new pixel is added to the class a palette entry defines, the palette entry is modified to take the means value of the pixels belonging to such class. In other improved palette coding modes, a built palette is post-processed to substitute a palette entry with a close entry of a palette predictor PRED. In yet other embodiments, palette coding modes having different threshold values to drive the building of their respective palettes are successively tested to use the best one in terms of rate-distortion criterion.

Abstract: The disclosure regards cross-component prediction and methods for obtaining a chroma sample from an associated luma sample using a linear model with parameters. The parameters are derived from luma and chroma samples neighbouring the luma and chroma blocks considered. The luma samples are down-sampled to match chroma resolution. A competition between several luma down-sampling schemes is proposed wherein two 1-tap filters are competing. This reduces computational complexity at the encoder. Also a competition between several sample sets defining the neighbouring luma and chroma samples used for parameter derivation is conducted, wherein a competing sample set is an irregular sample set. The irregular sample set preferably comprises only samples from second lines next to respective first lines of outer neighbouring samples parallel and immediately adjacent to respectively the left boundary and the top boundary of the current block. This improves chroma prediction and thus coding efficiency.

Abstract: A method of providing a mode value representing a prediction mode of at least part of an image to be encoded, the image being composed of a plurality of processing blocks, each processing block being predictable by applying a prediction mode of a plurality M of available prediction modes, the method comprising: determining first data indicative of a first set of n most probable prediction modes, from the plurality M of available prediction modes, for predicting the said at least part of an image; determining, for the case where a most probable prediction mode is not used, second data representative of a second set of prediction modes of the plurality M of available prediction modes wherein the second set of prediction modes comprise a restricted number N of prediction modes of the M available prediction modes, the prediction modes of the second set being selected from the M available prediction modes according to a predefined condition.

Abstract: The invention relates to the encoding or decoding of at least one portion of an image by predicting the at least one portion using at least one predictor, the at least one predictor being determined as a function of at least one reference image portion and as a function of values of a plurality of items of motion information. After having obtained a value of a first item of the plurality of items, a value of a second item is evaluated as a function of the obtained value of the first item, the second item being an item of the plurality of items and being distinct from the first item. Next, the at least one predictor is determined as a function of the at least one reference image portion and as a function of the first and second items.

Abstract: The invention concerns a method and a device for processing a current pixel block of an image using a palette prediction mode according to HEVC RExt. The mode uses a current palette to build a predictor block of indexes to predict the current pixel block. The current palette comprises entries associating entry indexes with pixel values. The method comprises predicting the current palette from entries of two or more palettes that are palettes previously used to process blocks of pixels. A palette predictor may be used that is built from the two or more palettes, preferably from the last used palette for a coding unit in the current coding entity and from the previously used palette for which a flag bitmap indicates whether or not its elements have been copied into the last used palette. Accordingly, the coding of the palette mode is improved.

Abstract: The disclosure regards cross-component prediction and methods for deriving of a linear model for obtaining a first-component sample for a first-component block from an associated reconstructed second-component sample of a second-component block in the same frame, the method comprising determining the parameters of a linear equation representing a straight line passing through two points, each point being defined by two variables, the first variable corresponding to a second-component sample value, the second variable corresponding to a first-component sample value, based on reconstructed samples of both the first-component and the second-component; and deriving the linear model defined by the straight line parameters; wherein said determining the parameters uses integer arithmetic.

Abstract: The disclosure regards cross-component prediction and methods for deriving of a linear model for obtaining a first-component sample for a first-component block from an associated reconstructed second-component sample of a second-component block in the same frame, the method comprising determining the parameters of a linear equation representing a straight line passing through two points, each point being defined by two variables, the first variable corresponding to a second-component sample value, the second variable corresponding to a first-component sample value, based on reconstructed samples of both the first-component and the second-component; and deriving the linear model defined by the straight line parameters.

Abstract: The invention relates to the valence-based encoding of connectivity data of a 3D mesh. A command is generated for each free edge of each vertex traversed and describes the vertex at the other end of the edge. The obtained list of commands is encoded by mapping each command onto a symbol. A mapping table associating commands with a set of respective consecutive numeral symbols is used. The list of symbols is then encoded, separately to the encoding of parameters of the commands. A joint encoding may be used to encode two or more consecutive symbols using a single coding word. A look-up table may be used based on the valence values intrinsically defined by each symbol, in order to give priority to the most frequent valence values (usually around 6). Prior to generating the commands, a vertex may be added to the 3D mesh to artificially fill any hole therein.

Abstract: A device for processing a current pixel block of an image using a palette prediction mode according to HEVC Format Range Extension (RExt). The mode uses a current palette to build a predictor block of indexes to predict the current pixel block. The current palette comprises entries associating entry indexes with pixel values. The method comprises predicting the current palette from entries of two or more palettes that are palettes previously used to process blocks of pixels. A palette predictor may be used that is built from the two or more palettes, preferably from the last used palette for a coding unit in the current coding entity and from the previously used palette for which a flag bitmap indicates whether or not its elements have been copied into the last used palette. Accordingly, the coding of the palette mode is improved.

Abstract: The disclosure regards cross-component prediction and methods for obtaining a chroma sample from an associated luma sample using a linear model with parameters. The parameters are derived from luma and chroma samples neighbouring the luma and chroma blocks considered. The luma samples are down-sampled to match chroma resolution. A competition between several luma down-sampling schemes is proposed wherein two 1-tap filters are competing. This reduces computational complexity at the encoder. Also a competition between several sample sets defining the neighbouring luma and chroma samples used for parameter derivation is conducted, wherein a competing sample set is an irregular sample set. The irregular sample set preferably comprises only samples from second lines next to respective first lines of outer neighbouring samples parallel and immediately adjacent to respectively the left boundary and the top boundary of the current block. This improves chroma prediction and thus coding efficiency.

Abstract: A method of performing sample adaptive offset (SAO) filtering on a sequence of images comprises associating a fixed set of four offset values with at least one direction of edge-type filtering. For every image area for which it is determined that edge-type filtering is to be used and for which it is determined that a direction of the edge-type filtering is the at least one direction, the fixed set of four offset values associated with said at least one direction is systematically used.

Abstract: The present invention provides a method and a device for coding and decoding at least a part of an image comprising a plurality of samples, each sample comprising at least two components, and the encoded image comprising at least one filtering parameter. The filtering comprises using at least one filtering parameter as a common filtering parameter for filtering both the first component and the second component of a reconstructed sample.

Abstract: The present invention concerns a method for encoding a video sequence, comprising the following steps by a processing unit of an encoding device: splitting an image from the video sequence into blocks of values; for each block: transforming the values of the block into transform coefficients; organizing these transform coefficients into several sets of transform coefficients; quantizing the transform coefficients into quantized coefficients; encoding the block using the quantized coefficients; encoding the video sequence based on the encoding of the blocks; ?wherein the quantizing step further comprises for quantized coefficients corresponding to one set of transform coefficients: determining scaled coefficients where a scaled coefficient is based on a transform coefficient of the one set, by multiplying the transform coefficient by a factor parameter and then adding a deadzone parameter, the deadzone parameter being scaled linearly with the index k of the transform coefficient within the set of transf

Abstract: A method of filtering a block of pixels in an image, comprising obtaining a first clipping control parameter (tc) value based on a quantization parameter of the block; comparing a first value of a first pixel located on one side of an edge in said block and a second value of a second pixel located on the other side of the edge in said block with a predetermined threshold derived from the first clipping control parameter value; and determining whether to apply a strong filtering to the first pixel based on the result of the comparison, wherein: the strong filtering comprises filtering the first pixel value so that the filtered first pixel value differs from the first pixel value by no more than a range value based on the clipping control parameter (tc), the ration between two range values corresponding to successive values of bitdepths being strictly lower than 2.

Abstract: The present disclosure concerns a method and a device for encoding or decoding video data. It concerns more particularly the encoding according to a particular encoding mode using a decoder side motion vector derivation mode referenced as frame-rate up conversion mode or FRUC mode. It concerns encoding and decoding improvement which reduce the need for memory accesses when using an encoding mode where the motion information is predicted using a decoder side motion vector derivation method.

Abstract: A method and a device for encoding or decoding video data. It concerns more particularly the encoding according to a particular encoding mode using a decoder side motion vector derivation mode referenced as frame-rate up conversion mode or FRUC mode. In FRUC merge mode, the derivation process comprises a refinement step to increase the accuracy of the obtained motion vector at the sub-pixel level. This process involves the evaluation of different sub-pixel position around the obtained motion vector according to different patterns. The present invention has been devised to improve the known refinement step. It aims at improving the coding efficiency by considering the characteristics of the matching type and/or the signal inside the templates.

Abstract: The value of a quantization parameter for at least one second color component of an image or image portion is determined using a current color format among several possible color formats. The determination comprises the steps of selecting at least one function associated with a possible color format, and determining the value of the quantization parameter for the second color component by applying said at least one function to a value of an intermediate quantization parameter which is based on the value of the quantization parameter of the first color component of the image or image portion. The at least one function is selected independently from the current color format.

Abstract: The present invention relates to encoding an image of a video stream according to at least one coding mode selected among a plurality of coding modes used to encode images of the video stream, where blocks of the image to be encoded are predicted as a function of at least one reference image from a set of at least one reference image, the at least one reference image comprising at least a reconstructed spatial portion of the image to be encoded and at least a low resolution portion of the image to be encoded, the choice between a reconstructed spatial sub-portion or a low resolution sub-portion to be used for encoding a block of the image to be encoded being determined as a function of a control parameter.

Abstract: A method of operating an encoder/decoder, and a device, for encoding/decoding a digital image into/from a video bitstream, said methods/device being arranged to: determine a parameter of an entropy code associated to one or more indexes of a block for encoding a coding unit of said digital image according to a palette, said palette comprising a set of indexes associated to pixel values, said entropy code being used for the encoding of at least part of said block, wherein an index of said block is encoded using a flag to indicate one of a plurality of modes for determining the value of the index, and the parameter of the entropy code is determined in dependence of which mode was indicated by the flag to determine the value of the index; and encode/decode said digital image into/from the video bitstream by using the determined parameter to adapt the entropy code.

Abstract: The present invention concerns a method for encoding a video sequence, comprising the following steps by a processing unit of an encoding device: splitting a digital image from the video sequence into blocks of values; for each block: transforming the values of the block into transform coefficients; organizing these transform coefficients into several sets of transform coefficients; quantizing the transform coefficients into quantized coefficients; encoding the block using the quantized coefficients; encoding the video sequence based on the encoding of the blocks; wherein the quantizing step further comprises for quantized coefficients corresponding to one set of transform coefficients: comparing a sum value representing a result of summing magnitudes of the quantized coefficient values with a threshold, the threshold depending on the number of the summed quantized coefficients, the quantized coefficient magnitudes being comprised within a predefined range; and setting the quantized coefficients to zer