Orange

France Telecom

Fondation B Com

B-com

Telediffusion De France

France Telecom Sa

Telediffusion De France S.a.

Pierrick Philippe

David Virette

Gordon Clare

Félix Henry

Mohsen Abdoli

Adria Arrufat

Patrice Collen

Julien Faure

Victorien Lorcy

Balazs Kovesi

Hendrik Vorwerk

Christophe Veaux

Claude Lamblin

Marc Emerit

Jean-Bernard Rault

Pierre Castel

Kevin Reuze

Adrià Arrufat

A method for decoding a coded data stream representative of at least one image that is split into blocks. For at least one block of the image, referred to as the current block, an item of information indicating a coding mode of the current block is decoded from the data stream. When the coding mode of the current block corresponds to a first coding mode, decoding a prediction residue associated with the current block using a first group of syntax elements. When the coding mode of the current block corresponds to a second coding mode, decoding the prediction residue associated with the current block using a second group of syntax elements, which is a subgroup of syntax elements of the first group of syntax elements.

Methods and devices for encoding and decoding a data stream representing at least one image

A method for decoding a coded data stream representing an image. The method includes for a current block: reading from the stream a block size threshold value; determining whether the current block size is less than or equal to the threshold value; if so, decoding information indicating a first or second coding mode and reconstructing the current block according to the indicated mode, and if not, reconstructing the current block according to the first mode. In the first mode the current block is reconstructed using an inverse transform of a transformed prediction residue decoded for the current block, and in the second mode the current block is not reconstructed using such an inverse transform, but by: scanning each pixel of the block, including: obtaining a prediction of the pixel from another previously decoded pixel, and reconstructing the pixel from the prediction and a decoded prediction residue.

Methods and devices for coding and decoding a data stream representing at least one image

A method for decoding a data stream representative of an image split into blocks. For a current block of the image, an item of information indicating a coding mode among a first and a second coding mode of the current block is decoded from the data stream and the current block is decoded depending on this information. When the coding mode of the current block corresponds to the second coding mode, the current block is reconstructed from a prediction obtained, for each pixel, from another previously decoded pixel belonging to the current block or to a previously decoded block of the image, and from a decoded residue associated with the pixel. At least one processing method is applied to the reconstructed current block for at least one pixel of the current block depending on the coding mode of the current block and/or the coding mode of the neighbouring blocks.

Methods and devices for encoding and decoding a data stream representing at least one image that disables post-processing of reconstructed block based on prediction mode

A method for decoding a digital image from encoded data representative of the image. The image is divided into blocks processed in a defined order. The method includes, for a current block having a predetermined number (Mv) of lines and number (Mh) of columns: decoding coefficients of the current block from coded data; decoding an index representative of an identifier of a transform among a plurality of transforms and identifying the transform, a transform being expressed as a vertical subtransform of size Mv*Mv and a horizontal subtransform of size Mh*Mh; transforming the current block into a decoded block transformed, from the transform obtained, by successive application of the vertical subtransform and then the horizontal subtransform or respectively of the horizontal subtransform and then the vertical subtransform; and reconstructing the image from the transformed decoded block. The transforming includes: a modified use of core sub-transform coefficients, their absolute values being retained.

Image decoding method, encoding method, devices, terminal equipment and computer programs therefor

A method for encoding or decoding at least one image, an image being split into blocks of elements. The method includes, for at least one block: splitting the block into at least two areas; and processing at least one of the areas. The processing includes scanning the elements of the area according to a predetermined scanning order, and for at least one scanned element, called a current element: selecting at least one predictor element previously encoded or decoded according to a prediction function; and predicting the current element: from the at least one predictor element, if the at least one predictor element belongs to the area; or from at least one replacement value, otherwise.

Method and device for coding and decoding an image by block cutting into zones

A method for decoding a data stream representative of an image split into blocks. The method includes: for a current block, determining whether the size of the current block is less than or equal to a threshold, and if so, decoding information indicating a coding mode of the block among first and second coding modes, and reconstructing the current block according to the indicated coding mode, and otherwise reconstructing according to the first coding mode. According to the first coding mode, the current block is reconstructed using an inverse transform of a transformed prediction residue decoded for the current block, and according to the second coding mode the current block is reconstructed, for each pixel, by obtaining a prediction of the pixel from another previously decoded pixel belonging to the current block or to a previously decoded block, and reconstructing the pixel from the prediction and a decoded prediction residue.

Encoding a digital image divided into a plurality of blocks of pixels processed in a defined order, including the following steps, implemented for a current block, with preset sizes: predicting values of the current block from at least one block previously processed; calculating a residual block by subtracting the predicted values from the original values of the current block; obtaining a residual block by applying a transform to pixels of the residual block, said transformed residual block comprising coefficients; encoding the transformed residual block; calculating at least one characteristic representative of at least one transformed residual coefficient of the current block; determining initial identification data representative of a sub-list of at least one transform associated with said at least one calculated characteristic; and verifying that the transform applied to the current block is part of the sub-list identified by the initial data.

Method for encoding a digital image, decoding method, devices, and associated computer programs

A method for decoding a data signal representative of at least one image cut into blocks. The method includes, for a current block to be decoded: transforming a residual data block obtained from the data signal; determining a permutation-transformation pair including a transformation mathematical operation and a permutation mathematical operation, the transformation mathematical operation and the permutation mathematical operation belonging to respectively a plurality of permutation operations and a plurality of transformation operations; applying the determined transformation mathematical operation to the data of the residual data block to produce transformed data; applying the determined permutation mathematical operation to the transformed data to produce permuted data, the determined permutation mathematical operation being an operation of transposing the transformed data; and using the permuted data to reconstruct the current block by a predictive decoding.

Method for encoding and decoding images, device for encoding and decoding images and corresponding computer programs

Method for encoding a digital image and verifying a transform applied to a current residual block, corresponding decoding method, devices, and associated computer programs

A method of coding at least one image sliced into blocks. The method implements, for a current block to be coded: predicting the current block in accordance with a prediction mode selected from among predetermined prediction modes, Intra and Inter, the selected mode of prediction being Intra; calculating a residual data block representative of a difference between a predictor block obtained on completion of the prediction and the current block; applying a transform operation to the data of the residual block, the transform operation belonging to a set of transform operations previously stored in association with the selected mode of Intra prediction; and coding the data obtained from the transform operation. The number of transform operations contained in the set associated with the selected Intra mode is different from the number of transform operations contained in a set of transform operations stored in association with the mode of Inter prediction.

Method of coding and decoding images, device for coding and decoding images and computer programmes corresponding thereto

A method and device for coding at least one current image parameter, wherein, in relation to a zone of a current image, the method implements the following: as a function of the value of at least one parameter of an image zone which precedes that zone of the current image, selecting a scheme for coding the at least one current image parameter, from among at least two predetermined coding schemes, and coding the value of the at least one current image parameter with the aid of the selected coding scheme.

Method for coding and decoding image parameters, device for coding and decoding image parameters and computer programs corresponding thereto

A method for decoding a current block of a digital image. The method includes: decoding coefficients of the current block; and transforming the current block into a decoded block, by implementing a first sub step to produce an intermediate block, that applies to the column and row vectors of the current block, and a second substep to produce a block of pixels that applies to the row and column vectors of the intermediate block, resulting from the first substep; and rebuilding the image from the decoded block. At least one of the first and second substeps includes, for an input row or column vector: forming a first subvector of size K&#x3c;N or N respectively from adjacent elements of the input vector; transforming the first subvector into a first transformed subvector by applying a partial subtransform of size K&#xd7;K; and building the transformed vector by inserting the first transformed subvector.

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Melesse, France

Pierrick Philippe