Device and method for motion-compensated recursive filtering of video images prior to coding and corresponding coding system

Device for the motion-compensated recursive filtering of video images before coding, comprising:

• means of storage (1) of at least one input image,
• a blockwise motion estimation module (2), designed to produce motion vectors (d) blockwise and quantities representative of variations in motion-compensated images (DFD), on the basis of a current input image and of at least one input image stored previously in the said means of storage,
• means (3) for determining a recursivity noise level (σrec) as a function of at least the said quantities representative of variations in motion-compensated images (DFD),
• a module (4) for calculating a prediction error (ε), between a current input image and an image predicted previously by filtering and motion compensation,
• a module (5) for calculating a recursivity coefficient (α) as a function of the said recursivity noise level (σrec) and of the said prediction error (ε),
• means (6) for calculating a motion-compensated image on the basis of a filtered image and of the said motion vectors (d),
• means of filtering (7, 8), intended to produce a weighting of the current input image and of a filtered and motion-compensated image stored previously, by the recursivity coefficient (α), and
• means of storage (6) of at least one filtered and motion-compensated image, produced by the means (6) for calculating motion-compensated images,
• characterized in that the said filtering device comprises:
• means (3) for determining an immobility noise level (σimm) as a function of at least the said quantities representative of variations in motion-compensated images (DFD), and
• an assembly (11, 12) for processing zones constituting partitions of the said blocks employed for the motion estimation, comprising:
• means of calculation (11) in the said zones, of quantities representative of variations in images preserved in space (FD), on the basis of a current input image and of at least one input image stored previously in the said means of storage (1) of input images, and
• means of zeroing (12) the motion vectors (d) associated with the said zones when the said quantities representative of variations in images preserved in space (FD) are below a threshold dependent on the immobility noise level (σimm).