Method of estimating motion in sequences of moving images using deformable meshes, video coder and decoder implementing the method

摘要

The invention concerns a method which consists in analyzing a field of motion of images, estimated by using a first mesh, to detect a faulty area in the first mesh, and in locating a rupture line in said area; then generating a second mesh including a faultless part consisting of meshes of the first mesh outside the faulty area and two sub-meshes which overlap in a region including the rupture line. Each of the two sub-meshes includes respective meshes delimited by nodes including nodes shared with the faultless part, located at the boundary of the faulty area, and additional nodes not belonging to the faultless part, the rupture line being located between the respective nodes of the two sub-meshes shared with the faultless part. Said second mesh is used to finally estimate the field of motion in the group of images concerned.

主权项

1. A method of estimating motion in a sequence of moving digital images, comprising the steps of:
generating a first mesh using a processor, comprising mesh cells delimited by nodes, to be applied to a reference image of the sequence; estimating a first displacement field in a group of images including the reference image, by assigning to each point of an image a displacement value calculated according to values assigned to the nodes delimiting a mesh cell of the first mesh to which said point belongs; detecting at least one discontinuity zone in the first mesh by analyzing the first displacement field, each discontinuity zone including at least one mesh cell fulfilling a mesh cell deformation criterion in the group of images; in each detected discontinuity zone, determining at least one break line appearing in the group of images; generating a second mesh using a processor to be applied to the reference image, the second mesh comprising a regular part made up of mesh cells of the first mesh which belong to no discontinuity zone and, for each detected discontinuity zone of the at least one detected discontinuity zone, at least two sub-meshes which overlap in a region including the at least one break line determined in each detected discontinuity zone, each of the at least two sub-meshes comprising respective mesh cells delimited by nodes including nodes shared with the regular part, situated at a boundary of each detected discontinuity zone, and additional nodes not belonging to the regular part, the at least one break line being situated between the respective nodes of the at least two sub-meshes shared with the regular part; and estimating a second displacement field in the group of images, by assigning to each point situated in a detected discontinuity zone a displacement value calculated according to values assigned to the nodes delimiting a selected mesh cell of the second mesh to which a latter point belongs, the selected mesh cell depending on the position of said latter point with respect to the break line determined in said discontinuity zone;wherein respective depth values are assigned to the nodes of the regular part and to the additional nodes of each sub-mesh of the second mesh, the value assigned to the additional nodes of a latter sub-mesh generated for a detected discontinuity zone being dependent on the position of said latter sub-mesh with respect to the at least one break line determined in said detected discontinuity zone, and wherein the step of estimating the second displacement field comprises, for each point of an image belonging to a mesh cell of the regular part of the second mesh and to at least one mesh cell of a sub-mesh, calculating, for each mesh cell including at least one point of said each point of an image belonging to a mesh cell of the regular part of the second mesh and to at least one mesh cell of a sub-mesh, a weighted sum of the depth values respectively assigned to the nodes delimiting said mesh cell, and selecting, for the assignment of a displacement value to said each point of an image belonging to a mesh cell of the regular part of the second mesh and to at least one mesh cell of a sub-mesh, the mesh cell for which the weighted sum calculated is a maximum.