Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-04-15
2001-10-16
Rao, Andy (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240170
Reexamination Certificate
active
06304603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a moving picture compression system, and more particularly, to a block matching method for estimating a motion vector value by moving a target window.
The present application for a block matching method by moving a target window is based on Korean Application No. 97-13874 which is hereby incorporated by reference for all purposes.
2. Description of the Related Art
Generally, redundancy of a moving picture is removed in order to compress the moving picture. In most moving picture compression systems which are currently used, such as MPEG and H.261, a motion estimation method is used to remove the redundancy. The motion vector shows the position difference between a reference block and a matching block by dividing a current frame into various small reference blocks, comparing each reference block with various search area blocks of a previous frame in a given search area, calculating a difference measure, to which the search area blocks are different to the respective reference blocks, and finding the block having the smallest difference measure (hereinafter referred to as a matching block). Then, the above motion vector and a pixel difference between the reference block and the matching block are transferred.
A blocking matching algorithm (BMA) which is widely used for moving picture compression calculates which block of a next image frame is most related to a block of a predetermined size of the current image frame, on the basis of a mean square error. With the BMA, a variation value close to optimal can be found as the range of the target window becomes wider and more search points are found. However, this needs a huge amount of calculation, which makes coding difficult to perform in real time.
Generally, the background of a moving picture is the portion of a screen in which the most precise motion vector can be estimated. This is because the block is not so complicated, and the BMA is based on the fact that a motion vector value has little difference to its adjacent motion vector values. Namely, the target window does not change. Objects move in the same direction (a background screen usually does not move), and in particular, the image of a picture phone has one object of motion. Such a situation is easily assumed during panning. Better estimation can be performed considering such a correlation between adjacent motion variation values. However, the above BMA method has limitations in estimating the motion vector since the motion vector is obtained without considering the correlation with the adjacent motion vectors.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a block matching method by which it is possible, by moving a target window, to estimate a better motion vector value using a target window of the same size, i.e., requiring the same amount of calculation, by appropriately moving the target window considering the correlation between adjacent variation values during estimation of the motion vector value of a BMA.
To achieve the above object, there is provided a block matching method of moving the target window, comprising the steps of (a) selecting a reference block Bm from a current frame Fn, by dividing the current frame Fn by a predetermined size, (b) determining the center point of a target window Wm for estimating a motion, obtained by dividing a previous frame F
n−1
by a predetermined size, to be the center point (X
n
,Y
n
) of the reference block Bm, (c) obtaining a motion vector (Dxn, Dyn) with respect to the reference block Bm, using the target window, (d) selecting the next reference block B
m+1
following the reference block Bm, the center point coordinates of which are (X
n+1
, Yn) in the current frame Fn, (e) determining whether the current frame Fn has a complicated motion, (f) obtaining a motion vector value using a predetermined general block matching method, when the current frame Fn has a complicated motion, (g) determining the center of a target window WW
m+1
for estimating the motion, corresponding to the B
m+1
in the previous frame F
n−1
, to be (X
n+1
+Dxn, Yn+Dyn), when the current frame Fn does not have a complicated motion, (h) determining whether the target window WW
m+1
, is within the boundary of the previous frame F
n−1
, (l) obtaining a motion vector (DDxn+1, DDYn), when the target window WW
m+1
is within the boundary of the previous frame F
n−1
, (j) obtaining a motion vector (DD
xn+1
, DDyn) after limiting the center of the target window WW
m+1
to be within the boundary of the previous frame F
n−1
, when the target window WW
m+1
, is not within the boundary of the previous frame F
n−1
, and (k) performing the steps (d) through (l) with respect to all the blocks of the current frame.
In the step (g), the center point O
m+1
(XX, YY) of the target window WW
m+1
in the previous frame F
n−1
for estimating the motion is determined when the current frame Fn does not have a complicated motion in the step (e), XX, which is the x-coordinate of the center point O
m+1
, is the value obtained by adding X
n
to the average values of the motion variation values in the x-axis direction of more than two blocks adjacent to the reference block Bm, and YY, which is the y-coordinate of the center point O
m+1
, is the value obtained by adding the Yn to the average values of the motion variation values in the y-axis direction of more than two blocks adjacent to the reference block Bm.
REFERENCES:
patent: 5585862 (1996-12-01), Wuertele et al.
patent: 5661524 (1997-08-01), Murdock et al.
patent: 5796434 (1998-08-01), Lempel
patent: 5818969 (1998-08-01), Astle
patent: 5990962 (1999-11-01), Ueno et al.
patent: 2-20988 (1990-01-01), None
patent: 4-323780 (1992-11-01), None
Rao Andy
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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