Abstract: A method and apparatus for improving the performance of video encoders and decoders involves selecting a set of transforms from among a plurality of sets of transforms that can be used for coding blocks in a region of a video image. Within a region, selection of a particular transform from among a plurality of transforms comprising the selected set of transforms is used to encoder or decode at least one block in the region. Associated indices representing the set of transforms to be used within a region and the selected transform for a block can be sent in a bitstream. In an alternate embodiment, a default set of transforms is complemented by selection of an additional set of transforms on a block or region basis.

Abstract: A decoding method is disclosed. The decoding method comprises: determining an index from a bitstream, the index identifying a coding element in a set of a plurality of coding elements; decoding a picture block from the bitstream using the coding element of the set identified by the index. In a specific embodiment, determining the index comprises: determining, for each coding element in the set, a probability that the coding element was used for encoding the picture block; and determining the index responsive to the determined probabilities.

Abstract: Coding of the last coded coefficient position is performed by basing the coding of they coordinate of the position of the last coded coefficient on knowledge of the size of the partial transform used to generate a block of coefficients from a block of video pixels. This enables a context adaptive coding of the last coded coefficient parameter to be performed much more efficiently.

Abstract: Coding of the last coded coefficient position is performed by basing the coding of they coordinate of the position of the last coded coefficient on knowledge of the size of the partial transform used to generate a block of coefficients from a block of video pixels. This enables a context adaptive coding of the last coded coefficient parameter to be performed much more efficiently.

Abstract: A method for decoding a bitstream representative of a picture is disclosed. Information representative of at least one encoding precision is first determined. A transform is then decoded responsive to the determined information. Finally, the picture is decoded using the decoded transform. A method for encoding a bitstream representative of a picture, as well as encoding devices and decoding devices are also disclosed.

Abstract: A method and apparatus for improving the performance of video encoders and decoders involves selecting a set of transforms from among a plurality of sets of transforms that can be used for coding blocks in a region of a video image. Within a region, selection of a particular transform from among a plurality of transforms comprising the selected set of transforms is used to encoder or decode at least one block in the region. Associated indices representing the set of transforms to be used within a region and the selected transform for a block can be sent in a bitstream. In an alternate embodiment, a default set of transforms is complemented by selection of an additional set of transforms on a block or region basis.

Abstract: A decoding method is disclosed. The decoding method comprises: determining an index from a bitstream, the index identifying a coding element in a set of a plurality of coding elements; decoding a picture block from the bitstream using the coding element of the set identified by the index. In a specific embodiment, determining the index comprises: determining, for each coding element in the set, a probability that the coding element was used for encoding the picture block; and determining the index responsive to the determined probabilities.

Abstract: Coding of the last coded coefficient position is performed by basing the coding of they coordinate of the position of the last coded coefficient on knowledge of the size of the partial transform used to generate a block of coefficients from a block of video pixels. This enables a context adaptive coding of the last coded coefficient parameter to be performed much more efficiently.

Abstract: Coding of the last coded coefficient position is performed by basing the coding of they coordinate of the position of the last coded coefficient on the x coordinate value of the last coded coefficient. This enables the context adaptive coding of the last coded coefficient parameter much more efficient. In an embodiment, a partial transform is used to code a block of image values. The partial transform enables further efficiencies in coding of the last coded coefficient.

Abstract: Some embodiments are directed to a method for encoding a dynamic texture region of a video sequence, said video sequence including a plurality of video frames and each video frame including at least one coding block. The method includes a rate-distortion optimization step in a coding loop based on a measured distortion value (SSD). According to the invention, the rate-distortion optimization includes the steps of estimating, for at least one current coding block of dynamic texture to be encoded, a perceived distortion value (SSDp), replacing the distortion value (SSD) measured for said current coding block of dynamic texture by said estimated perceived distortion value (SSDp), and applying the rate-distortion optimization step with said estimated perceived distortion value.

Abstract: Some embodiments are directed to a method and a device for encoding a current frame of a video sequence, the current frame being encoded block by block. A current block of the current frame is encoded by performing: applying a texture synthesis to the video sequence in order to generate a set of n candidate blocks for replacing the current block, the n candidates blocks being similar to the current block according to a predefined criterion, encoding the candidate blocks in order to generate encoded candidate blocks and computing a coding cost for each encoded candidate block, and selecting as encoded block for the current block the encoded candidate block having the lowest coding cost.

Abstract: A method for decoding a bitstream representative of a picture is disclosed. The decoding method comprises:—determining information representative of at least one encoding precision;—decoding a transform responsive to said determined information;—decoding said picture using the decoded transform.

Abstract: A method for determining objectively a visual quality index of at least one high dynamic range video sequence, referred to as an HDR sequence, distorted by image processing operations and issued from a reference high dynamic range video sequence, referred to a reference sequence or a reference HDR sequence. The method is based on signal pre-processing, transformation, and subsequent frequency based decomposition. Video quality is then computed based on a spatio-temporal analysis that relates to human eye fixation behavior during video viewing. One advantage of this method is that it does not involve expensive computations.

Abstract: A method for determining objectively a visual quality index of at least one high dynamic range video sequence, referred to as an HDR sequence, distorted by image processing operations and issued from a reference high dynamic range video sequence, referred to a reference sequence or a reference HDR sequence. The method is based on signal pre-processing, transformation, and subsequent frequency based decomposition. Video quality is then computed based on a spatio-temporal analysis that relates to human eye fixation behavior during video viewing. One advantage of this method is that it does not involve expensive computations.

Abstract: A method for assessing the quality of a distorted version of a frame sequence includes the steps of determining a last spatial distortion by comparing a block of a last frame (I6) of the sequence with a corresponding block of the distorted version of the last frame, determining, in a last-but-one frame, a best-matching block matching said block of the last frame best, determining a last-but-one spatial distortion by comparing the determined best-matching block of the last-but-one frame with a corresponding block of the distorted version of the last-but-one frame, determining a spatio-temporal perceptual distortion value associated with said block using said determined distortions and using the determined spatio-temporal perceptual distortion value for assessing the quality.

Abstract: Detection of the salient points in an image enable the improvement of further steps such as coding or image indexing, watermarking, video quality estimation. The methods rely on the fact that a model is fully based on the human visual system (HVS) such as the computation of early visual features, and the methods compute a saliency map for video images taking into account motion and the velocity of the eye.

Abstract: A method of obtaining a saliency map from a plurality of saliency maps created from different visual quantities. Initially the saliency maps are normalized based on a theoretical maximum of each visual quantity. An intra-competition step selects the main saliency areas in each saliency map. An inter-competition step is then performed based on a sum of the intra-map competition with an inter-map redundancy term that is a function of the product of the intra-map competitions and of the probability of a site appearing on the saliency maps.

Abstract: A method for assessing image quality between a reference image and an impaired image is disclosed. The method comprises the steps of subband decomposition of the luminance component of the reference image into N subbands, called reference subbands and of the luminance component of the impaired image into N subbands, called impaired subbands; errors computation from the reference subbands and from the impaired subbands; and pooling the computed the errors. The subband decomposition is based on a wavelet transform adapted to decompose each of the luminance components into L levels of decomposition, with L a positive integer determined as a function of the image height and of the distance of visualization.

Abstract: The invention is a method for assessing image quality value of a distorted image with respect to a reference image. The method comprises the following steps: computing, for each pixel of the distorted image, at least one quality level with respect to the reference image; adding, for the distorted image, the quality levels associated to each pixel by weighting them by a weight depending on a perceptual interest of the pixel in order to get the image quality value, the weight being lower for a pixel of high perceptual interest.

Abstract: The invention concerns a device and a method for creating a saliency map of an image. It comprises the steps of: Projection of said image according to the luminance component and if said image is a color image, according to the luminance component and according to the chrominance components, Perceptual sub-bands decomposition of said components according to the visibility threshold of a human eye, Extraction of the salient elements of the sub-bands related to the luminance component, Contour enhancement of said salient elements in each sub-band related to the luminance component, Calculation of a saliency map from the contour enhancement, for each sub-band related to the luminance component. Creation of the saliency map as a function of the saliency maps obtained for each sub-band.