Image analysis – Image compression or coding – Interframe coding
Patent
1995-12-18
1998-04-07
Couso, Yon J.
Image analysis
Image compression or coding
Interframe coding
382240, 348413, G06K 936
Patent
active
057374473
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for hierarchical estimation of the motion of image sequences.
It applies in particular to the production of image transmission chains with a view to reducing the bit rate of the information transmitted.
2. Description of the Background
A process and a device for estimation and hierarchical coding of motion in image sequences is known from French Patent Application No. 89 11328 filed in the name of THOMSON CONSUMER ELECTRONICS. This process is executed in accordance with several levels of processing. It includes according to a first level partitioning the current image into macroblocks of 2.sup.P+1.2.sup.p+1 pixels and in determining a first motion vector field, associated with this macroblock splitting, by using an iterative and recursive estimation algorithm initialized with motion vectors estimated for the preceding image. It consists according to a second level in partitioning each of the macroblocks into quadrants and in determining, for the blocks which result from this, a second motion vector field using the same estimation algorithm but initialized with vectors from the motion field estimated at the preceding level. Then at an i.sup.th level, it consists in partitioning each of the blocks considered at level i-1 into quadrant and in determining, for the blocks which result from this, an i.sup.th motion field using the same estimation algorithm initialized with vectors from the motion field estimated at the preceding level, the minimum size blocks being blocks of 2.sup.l+1.2.sup.l+1 pixels. Lastly, it includes in determining a final motion vector field from the resulting motion vector fields by choosing the least high level of splitting for which the motion vector associated with the corresponding block leads to the minimization of a criterion conveying the differences in luminance between blocks corresponding to one another in the successive images via the estimated displacement vectors.
This process makes it possible to enhance the convergence of the recursive motion estimation algorithm used and to best adapt the motion estimation algorithm to the "quadtree" type coding used subsequently to code the resulting motion field. However, execution of the temporal loop of the algorithm turns out to consume a great deal of calculation time and its implementation in an HD.MAC coder requires too large a number of electronic components to be easily integrated with this type of coder.
SUMMARY OF THE INVENTION
The object of the invention is to alleviate the aforesaid drawbacks.
For this purpose, the subject of the invention is a device for hierarchical estimation of the motion of image sequences, characterized in that it includes a set of cascaded processing macromodules and organized in accordance with hierarchical levels, each macromodule being structured so as to partition the current image into macroblocks of a determined size corresponding to its hierarchical level so as to transmit a motion vector field to the block which follows it, the device comprising first circuits for calculating displaced inter-image differences DFDi and gradients based on luminance values of pixels of a video image and displacement vectors of each image preceding or following a current image; second circuits for performing blockwise summations of the displaced inter-image differences; and third circuits for performing corrections of the displacement vectors of the image.
The main advantage of the invention is to offer a model of hardware architecture which is simpler to produce than that of the prior devices together with a sharply reduced number of processing levels and much smaller calculation times.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention will emerge with the aid of the description which follows given in connection with the appended figures which represent:
FIG. 1 an embodiment of a device for hierarchical estimation of motion according to the invention;
FIG. 2 an embodiment of
REFERENCES:
patent: 4849810 (1989-07-01), Ericsson
patent: 5122873 (1992-06-01), Golin
patent: 5296927 (1994-03-01), Guillotel
patent: 5351095 (1994-09-01), Kerdranvat
patent: 5414469 (1995-05-01), Gonzalez et al.
patent: 5541661 (1996-07-01), Odaka et al.
Aubie Jean-Yves
Bourdon Fran.cedilla.ois
Guillotel Philippe
"Thomson-CSF"
Couso Yon J.
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