Abstract: The invention relates to an encoding method for the compression of a video sequence divided in flames decomposed by means of a wavelet transform. Said method, based on the hierarchical subband encoding process called “set partitioning in hierarchical trees” (SPIHT), leads from the original set of picture elements of the video sequence to wavelet transform coefficients encoded with a binary format. These coefficients are organized in trees and ordered into partitioning sets respectively corresponding to levels of significance, by means of magnitude tests leading to a classification into three ordered lists called list of insignificant sets (LIS), list of insignificant pixels (LIP) and list of significant pixels (LSP). According to the invention, a specific initialization order of the LIS is proposed.

Abstract: The invention relates to a video coding method applied to a sequence of frames and based on a tridimensional (3D) wavelet decomposition with motion estimation and compensation on couples of frames. The method comprises the steps of organizing the wavelet coefficients resulting from said decomposition in a structure of macroblocks, separated by resolution flags, and blocks with a size fitting the lowest approximation sub-band of the decomposition, scanning the coefficients of each 3D macroblock in a predefined order connected to the spatial orientation and the location of each of its blocks, and encoding said scanned coefficients bitplane by bitplane. Moreover, the encoding step includes a global bitrate allocation sub-step between the macroblocks, by means of a global distortion minimization.

Abstract: The invention relates to the field of video encoders and, more particularly, to an encoding method based on an adaptation of the matching pursuit method to an error texture coding process inside triangular meshes. Said process is restricted, at each iteration of the method, to a specific triangle selected according to a predefined criterion. An optimal strategy for atom positioning inside this triangle then consists either in arbitrarily selecting the geometrical barycenter of the selected triangle as the center of the atoms, or re-using the error energy information for atom center positioning, the Displaced Frame Difference (DFD) energy barycenter inside the selected triangle having the highest energy being in the second case arbitrarily chosen as the center of the atoms.

Abstract: The invention relates to a method of coding motion information associated to an image sequence, comprising the steps of subdividing each image into blocks and applying to each block a block-matching algorithm for defining a shifted block as the prediction of the current block, the motion vector between said shifted and current blocks being the predicted vector associated to said current block and all the motion vectors similarly predicted for a whole current image constituting a motion vector field associated to said current image. For each current image, the motion information constituted by said associated motion vector field is finally coded. According to the invention, the motion vector C to be coded is approximated by a spatio-temporal predictor P defined by a relation of the type: P=&agr;·S+&bgr;·T, where S and T are spatial and temporal predictors respectively, and (&agr;, &bgr;) are weighting coefficients respectively associated to said spatial and temporal predictors.

Abstract: The invention relates to an encoding method for the compression of a video sequence divided into groups of frames decomposed by means of a tridimensional wavelet transform. According to this method, based on the hierarchical subband encoding process SPIHT and applied to the band-pass subbands of a spatio-temporal orientation tree defining the spatio-temporal relationship within the hierarchical pyramid of the obtained transform coefficients, a vectorial DPCM, using either constant prediction coefficients or adaptive ones for taking into account scene changes, is used to separately encode the lowest frequency spatio-temporal subband, and the quantification of the prediction error observed when constructing a spatio-temporal predictor for each vector of transform coefficients having components in each frame of said subband is carried out by means of a scalar or vectorial quantization.

Abstract: The invention relates to scalable video encoders, and, more precisely, to an encoder comprising a base layer and at least an enhancement layer circuit, said circuits being capable of generating enhancement layer video data associated with compressed base layer video data and suitable for transmission to a video decoder. In said encoder, the implemented encoding method, based on a hierarchical triangular mesh representation to which a matching pursuit error coding step is specifically adapted, comprises a base layer encoding step and enhancement layer encoding steps.

Abstract: The invention relates to an encoding method for the compression of a video sequence. Said method, using a three-dimensional wavelet transform, is based on a hierarchical subband coding process in which the subbands to be encoded are scanned in an order that preserves the initial subband structure of the 3D wavelet transform. According to the invention, a temporal (resp. spatial) scalability is obtained by performing a motion estimation at each temporal resolution level (resp. at the highest spatial resolution level), and only the part of the estimated motion vectors necessary to reconstruct any given temporal (resp. spatial) resolution level is then encoded and put in the bitstream together with the bits encoding the wavelet coefficients at this given temporal (resp. spatial) level, said insertion in the bitstream being done before encoding texture coefficients at the same temporal (resp. spatial) level.

Abstract: The invention relates to a video coding method applied to a sequence of frames and based on a tridimensional (3D) wavelet decomposition with motion estimation and compensation on couples of frames. The method comprises the steps of organizing the wavelet coefficients resulting from said decomposition in a structure of macroblocks, separated by resolution flags, and blocks with a size fitting the lowest approximation sub-band of the decomposition, scanning the coefficients of each 3D macroblock in a predefined order connected to the spatial orientation and the location of each of its blocks, and encoding said scanned coefficients bitplane by bitplane. Moreover, the encoding step includes a global bitrate allocation sub-step between the macroblocks, by means of a global distortion minimization.

Abstract: The invention relates to a method for encoding a video sequence subdivided into groups of frames. This method comprises an on-line procedure in which a three-dimensional wavelet decomposition is performed involving a biorthogonal filter bank in a lifting scheme using optimal weighting constants. These constants are determined thanks to an additional off-line procedure in which a similar decomposition is performed but without any weighting constants.

Abstract: In order to compress a video sequence under the constraint of scability, the known 2D or 3D SPIHT, based on the prediction of the absence of significant information across scales of a wavelet decomposition, compares a set of pixels, corresponding to the same image area at different resolutions, to a value called level of significance. In both cases, the transform coefficients are ordered by means of magnitude tests involving the pixels represented by three ordered lists called list of insignificant sets (LIS), list of insignificant pixels (LIP) and list of significant pixels (LSP). In the original video sequence, the value of a pixel depends on those of the pixels surrounding it. The estimation of the probability of a symbol given the d previous bits becomes a difficult task when the number of conditioning events increases.

Abstract: The invention relates to a method for encoding a sequence of frames by means of a three-dimensional (3D) subband decomposition involving a spatial and temporal filtering step. The decomposition is applied to successive groups of frames only after the implementation, on the frames, of motion estimation and compensation operations in the low temporal subbands at each level of the temporal decomposition. A motion compensated temporal filtering step between a previous reference frame A and a current frame B comprises in a first time a computation sub-step of the high frequency subband, followed by a computation sub-step of the low frequency subband.

Abstract: The invention relates to an encoding method for the compression of a video sequence by means of a tridimensional wavelet transform. This method is based on a hierarchical subband encoding process leading to transform coefficients constituting a hierarchical pyramid. A spatio-temporal orientation tree, in which the roots are formed with the pixels of the approximation subband and the offspring of each of these pixels is formed with the pixels of the higher subbands, defines the spatio-temporal relationship inside said pyramid. According to the invention, the initial subband structure of the wavelet transform is preserved, in the encoding process, by scanning the subbands one after the other in an order that respects the parent-offspring dependencies formed in the tree.

Abstract: The invention relates to an encoding method for the compression of a video sequence which is organized in groups of frames decomposed by means of a wavelet transform. The method is based on the hierarchical subband encoding process SPIHT that transforms the original set of picture elements (pixels) into coefficients ordered by means of three ordered lists called list of insignificant sets (LIS), list of insignificant pixels (LIP) and list of significant pixels (LSP).

Abstract: The invention relates to an encoding method for the compression of a video sequence divided in flames decomposed by means of a wavelet transform. Said method, based on the hierarchical subband encoding process called “set partitioning in hierarchical trees” (SPIHT), leads from the original set of picture elements of the video sequence to wavelet transform coefficients encoded with a binary format. These coefficients are organized in trees and ordered into partitioning sets respectively corresponding to levels of significance, by means of magnitude tests leading to a classification into three ordered lists called list of insignificant sets (LIS), list of insignificant pixels (LIP) and list of significant pixels (LSP). According to the invention, a specific initialization order of the LIS is proposed.

Abstract: The invention relates to the field of video encoders and, more particularly, to an encoding method based on an adaptation of the matching pursuit method to an error texture coding process inside triangular meshes. Said process is restricted, at each iteration of the method, to a specific triangle selected according to a predefined criterion. An optimal strategy for atom positioning inside this triangle then consists either in arbitrarily selecting the geometrical barycenter of the selected triangle as the center of the atoms, or re-using the error energy information for atom center positioning, the Displaced Frame Difference (DFD) energy barycenter inside the selected triangle having the highest energy being in the second case arbitrarily chosen as the center of the atoms.