Patent FR-2822331-A1 (FR)
Title: Method and device for coding/decoding of digital signal with hierarchical segmentation, for use in particular for digital images and video sequences
Inventor: AMONOU ISABELLE
IPC: H04N7/26
Filed: 2001-03-19
Abstract: The method for coding a set of data representative of physical quantities comprises the steps of decomposing (E1) the set of data onto a number (N) of resolution levels, and for each resolution level the segmentation (E2) of data of that level into at least two homogeneous regions, the initialization (E3) of parameter i indicating the current resolution level (N-i), where N is the total number of levels, the classification (E4) of the regions according to a priority criterion, and for each region deciding the coding of that region as a function of the classification and a predetermined coding criterion, the coding (E5) of mask (MSN-i) computed for the current resolution level, the coding (E6) of the regions of the current resolution as a function of the mask, a test (E7) if the parameter i is equal to N-1, that is if all levels have been treated, and incrementing (E8) the parameter i by unity if at least one level remains to be treated.  The decomposition (E1) of the set of data is by a Discrete Wavelet Transform (DWT). The coding criterion consists of selecting K first classified regions, where K is a predetermined integer, or an integer determined as a function of the transmission rate of coded data. The classification (E4) of the regions is effected by describing a spiral from the centre of zone comprising the regions to be classified. The decision (E4) for coding a region consists in deciding if the region is coded or not. The result of the decision of coding a resolution level is a binary mask, and the binary mask of at least one lower resolution level is coded. The second embodiment of coding method comprises the additional steps of decoding the coded regions and the synthesis of decoded regions on a resolution level; the steps of segmentation, classification, decision, coding/decoding, and synthesis are effected on the data of a lower resolution level for the first iteration, and then on the result of the synthesis of preceding iteration, from the second iteration. A method for decoding the set of coded data comprises the steps of decoding a binary mask representative of the result of coding decision, the decoding of coded coefficients of the regions, and the synthesis of decoded coefficients on at least one resolution level. The second embodiment of decoding method comprises the additional steps of segmenting the synthesized data in at least two homogeneous regions, the classification of the regions according to the priority criterion, and the decision of coding for each region. A device for coding the set of data implements the coding method in the first embodiment, or in the second embodiment. A device for decoding the set of coded data implements the decoding method in the first embodiment, or in the second embodiment. The device for coding/decoding incorporates a microprocessor, a read-only memory (ROM) comprising a program for data processing, and a ran dom-access memory (RAM) comprising registers for variables modified in the course of program execution. An apparatus for digital signal processing comprises means for implementing the method, or comprises the device.