Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-02-06
1991-10-22
Kostak, Victor R.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358140, H04N 701
Patent
active
050600648
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arrangement for interpolating images by motion estimation and compensation, which arrangement includes a block-by-block motion estimation member to form motion vectors assigned to blocks of picture elements an and an interpolation member to form an image as a function of said motion vectors.
Arrangements of this type are used with great advantage, more specifically in the field of television. By knowing the motion vectors which define the displacement of the different successive picture elements, it is possible to form by interpolation an image of a good quality at an instant chosen between two consecutive images.
2. Description of the Related Art
This type of arrangement for which a motion estimation is used for an overall block of picture elements is well known. For this subject, reference is made to the article by C. CAFFORIO and ROCCA, entitled: "The differential method for image motion estimation" in Image sequence processing and dynamic scene analysis, T. S. Huang Ed., Berlin, Germany, Springer-Verlag, 1983, pp. 76-103.
If the blocks contain many picture elements, a first disadvantage is met. This disadvantage is caused by the fact that it may happen that picture elements of the same block are displaced from one image to the other by a clearly different amount, which consequently results in interpolated images of a poor quality.
When the blocks contain few elements, there is a second disadvantage as the motion estimation may be affected by noise and an image of a poor quality is obtained also then.
SUMMARY OF THE INVENTION
The present invention has for its object to provide an arrangement of the type defined above which supplies a motion vector for all the elements or some elements while remaining insensitive to noise.
To that end, such an arrangement is characterized in that it includes an assigning member for assigning one vector from candidate motion vectors processed by the estimation member for at least one image element denoted the current element.
The present invention also relates to a television standard converter system formed on the basis of such an arrangement. An example of a conversion is the example in which images appearing at a rate of 50 Hz are converted into images appearing at the rate of 60 Hz (or 59.94 Hz). It is, consequently, impossible to have the images coincide; the images to be formed at the rate of 59.94 Hz are obtained by interpolation of images appearing at 50 Hz. The following articles describe systems of this type: "Movement-compensated frame-frequency conversion of television signal" HOIROHISA YAMAGUCHI et al. IEEE Transactions on Communications, vol. COM-35, no. 10, October 1987. "HDTV-PAL Standards Converter" YUTALEA TANAKA et al. NHK Laboratories Note, January 1986, no. serie 326.
The quality of the images provided by these systems are based to a large extent on an appropriate valuation of the motion vector.
To interpolate sequences of images, an important characteristic of the invention in accordance with which an arrangement of the type defined above comprises a motion vector coherence test member to supply a validation signal for each motion vector assigned to an element, by comparing it with corresponding elements positioned in images of said sequence, provides the advantage that certain ambiguities in the determination of the motion vector are avoided. These ambiguities occur more specifically for small sized objects which move on a continuous background. Certain portions of the object will be provided with a good motion vector but other objects may be provided with a motion vector corresponding to the background.
The interpolated image will show discontinuities in the reproduction of this object and these discontinuities will appear in different locations of the image during an image sequence. The object will finally appear in a degraded quality. Thanks to this characteristic of the invention, this degradation and these discontinuities are prevented to a large exten
REFERENCES:
patent: 4442454 (1984-04-01), Powell
patent: 4777530 (1988-11-01), Kondo
patent: 4853775 (1989-08-01), Rouvrais et al.
"Determining Velocity Maps by Spatio-Temporal Neighborhoods from Image Sequences" Yachido; Computer Vision, Graphics, and Image Processing 21; pp. 262-279; Feb. '83.
Lamnabhi Moustanir
Lhuillier Jean-Jacques
Goodman Edward W.
Kostak Victor R.
U.S. Philips Corporation
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