Method and apparatus for motion estimation

Television – Image signal processing circuitry specific to television – Motion vector generation

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H04N 736

Patent

active

054899494

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a method and apparatus for motion estimation, and more particularly relates to a method and apparatus for further a detailed motion estimation, in which uses an error value generated at an estimation of motion for determining a motion vector, in especially differential pulse code modulation (DPCM) method for coding a digital image signal.


DESCRIPTION OF RELATED ART

Generally, there are several coding methods for further efficiently compressing transmission data in an image signal processing apparatus using subsequent digital image signals, such as high definition television (HDTV), Digital VTR (digital video tape recorder), and multi-media, etc. The DPCM method, which codes the digital image signal using data correlations which are present between adjacent frames of the image signal.
In the case of coding a difference signal between adjacent frames representing different times using the DPCM method, it is disadvantageous that much more data needs to be coded for an active image rather than a still image. However, by recognizing a movement location from a certain block of the previous frame to a specific block in the present frame, that is, the best similarity between a specific image of the present frame and a certain image of the previous frame, efficient data compression can be performed because signal difference values of similar blocks between frames can be minimized. Accordingly, in the motion estimation using the DPCM method, difference data between a predetermined image block of the previous frame and the corresponding image block of the present frame is coded, thereby permitting efficiency of the transmission to be enhanced. In the motion estimation method, a motion vector represents a moving direction and magnitude of the image block obtained by comparing an image block within the present frame with the corresponding image block of the previous frame.
There are several methods for generating motion estimates in terms of a pixel unit. Generally, since motion between two frames separated in time may be small with respect to an integer-pixel unit, errors may be introduced during motion compensation when using the motion vector of an integer-pixel unit. Therefore, a motion vector of a sub-pixel unit is used for reducing motion compensation errors. A half-pixel unit, as one estimation method of sub-pixel units, is commonly used for the motion estimation. A motion estimation method using a half-pixel unit in accordance with a conventional method win be briefly described.
The apparatus of FIG. 1 comprises N.sub.1 .times.N.sub.2 block constructor 1 for receiving an image signal of the present frame and constructing an image block composed of N.sub.1 .times.N.sub.2 pixels; M.sub.1 .times.M.sub.2 search range constructor 2 for receiving the image signal of the previous frame and constructing the image block composed of M.sub.1 .times.M.sub.2 pixels; a first search unit 3 for receiving the image signals output from the N.sub.1 .times.N.sub.2 block constructor 1 and the M.sub.1 .times.M.sub.2 search range constructor 2 and detecting a first motion vector MV1 of a pixel unit; a half-pixel interpolating unit 4 for receiving image signals output from the M.sub.1 .times.M.sub.2 search range constructor 2 and the first search unit 3 and calculating an image signal value in a half-pixel location around reference pixels, using the image block within the previous frame which is determined by the first motion vector MV1 detected from the first search unit 3 and the image blocks which are obtained by moving the image block at intervals of one pixel; a second search unit 5 for receiving the image signals output from the N.sub.1 .times.N.sub.2 block constructor 1 and the half-pixel interpolating unit 4 and outputting a second motion vector MV2 of a half-pixel unit; and a summing unit 6 for receiving and summing the output signals MV1, MV2 from the first search unit 3 and the second search unit 5, respectively, and outputting a motion vector MV.
The N.sub.1 .time

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patent: 5241608 (1993-08-01), Fogel
patent: 5280351 (1994-01-01), Wilkinson
patent: 5289274 (1994-02-01), Kondo

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