Patent ID: 7031533
Filing Date: 2006-04-18
Classification: H04N

Abstract:
1. An encoding method for the compression of a video sequence divided in groups of frames decomposed by means of a three-dimensional (3D) wavelet transform leading to a given number of successive resolution levels corresponding to the decomposition levels of said transform, said method being based on a hierarchical subband encoding process leading from the original set of picture elements (pixels) of each group of frames to transform coefficients constituting a hierarchical pyramid, and a spatio-temporal orientation tree —in which the roots are formed with the pixels of the approximation subband resulting from the 3D wavelet transform and the offspring of each of these pixels is formed with the pixels of the higher subbands corresponding to the image volume defined by these root pixels—defining the spatio-temporal relationship inside said hierarchical pyramid, said encoding method comprising the steps of: (A) preserving the initial subband structure of the 3D wavelet transform by scanning the subbands one after the other in an order that respects the parent-offspring dependencies formed in said spatio-temporal tree; (B) adding “off/on” flags to each coefficient of the spatio-temporal tree in view of a progressive transmission of the most significant bits of the coefficients, these flags being such that at least one of them describes the state of significance of a set of pixels and at least another one describes the state of significance of a single pixel, wherein two flags describe the state of significance of a set of pixels and are, for each coefficient (x,y,z) of said spatio-temporal tree: where D(x,y,z) is the set of coordinates of all the descendants of the node (x,y,z) and L(x,y,z)=D(x,y,z)−O(x,y,z), with O(x,y,z) is the set of coordinates of the direct offspring of the node (x,y,z), and two flags describe the state of significance of a single pixel and are: FP FP