Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-12-22
2001-10-02
Le, Vu (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240170, C348S699000
Reexamination Certificate
active
06298086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motion vector detecting apparatus suitable for use in an image processing system such as an H. 261 system, an MPEG (Moving Picture Experts Group) system or the like, wherein a motion vector relative to an already-coded frame is detected for each of blocks into which a frame of image data is divided.
2. Description of the Prior Art
FIG. 33
is a block diagram showing a motion vector detecting apparatus according to a conventional example 1 described in, for example, JP-A No. 6-113290. In the drawing, reference numeral
1
indicates an already-coded frame memory which is employed in an image processing system such as an H. 261 system, an MPEG system or the like and stores therein pixel data of a frame already coded by interframe prediction coding, i.e., pixel data for prediction of a frame coded at the present time. Upon prediction of the frame coded at the present time, a motion vector relative to each of blocks into which the coded frame is divided, is detected. Namely, horizontal and vertical distances between the position of each block in the frame coded at the present time and the position of a range corresponding to each block in the already-coded frame are detected as a motion vector.
Reference numerals
101
-J (where J=0, . . . , 7) respectively indicate search window row memories for respectively storing pixel data lying in a row shifted by a column component of a predetermined search vector from the position of each of blocks in a search window corresponding to a range for searching a range corresponding to each block in the coded frame. The coded frame will be divided into blocks of 8 rows and 8 columns herein. Further, the search window will be defined as a range set when the blocks are respectively shifted from side to side by 16 pixels at maximum and shifted upward and downward by 8 pixels at maximum. Incidentally, the search vector represents horizontal and vertical distances from the position of each block referred to above to a range of pixel data to be compared with pixel data in the block. Here, the search vector corresponds to any of (−16, −8) through (+16, +8).
Reference numeral
102
indicates a search window shift register unit having shift registers constructed so that registers
103
-(0, J) through
103
-(7, J) are series-connected to their corresponding search window row memories
101
-J by the number of columns.
Reference numeral
5
indicates a coded frame memory for storing data about pixels in a frame coded at the present time. Reference numeral
6
indicates a reference register unit for allowing registers
12
-(I, J) to store data about respective pixels of Ith rows and Jth columns (where I=0, . . . , 7, and J=0, . . . , 7) in any (hereinafter called “reference block”) of blocks of 8 rows and 8 columns, into which the frame coded at the present time is divided. Incidentally, pixels extending from the mth row and nth column to the (m+7)th row and (n+7)th column in the frame constitute each reference block.
Reference numeral
4
indicates an evaluation unit having pixel comparators
13
-(I, J) for respectively comparing the pixel data of the respective registers
12
-(I, J) of the reference register unit
6
and the pixel data of the registers
103
-(I, J) constituting the shift registers of the search window shift register unit
102
.
Reference numeral
7
indicates a motion vector detection unit for detecting the optimum search vector as a motion vector, based on the results of comparisons by the respective pixel comparators
13
-(I, J) of the evaluation unit
4
. For example, the differences between the respective two pixel data are calculated by the respective pixel comparators
13
-(I, J) and a search vector at the time that the sum of absolute values of their differences is minimum, is defined as a motion vector.
The operation will next be described.
First, the already-coded frame memory
1
supplies any pixel data of 8 rows of the search window to their corresponding search window row memories
101
-
0
through
101
-
7
.
Thereafter, the search window row memories
101
-
0
through
101
-
7
output pixel data constituting one-row pixel data supplied thereto to their corresponding registers
103
-(0, 0) through
103
-(0, 7) of the search window shift register unit
102
in order for each clock.
The respective registers
103
-(I, J) of the search window shift register unit
102
supply the stored pixel data to the next-stage registers
103
-(I+1, J) and the pixel comparators
13
-(I, J) of the evaluation unit
4
for each clock and store the pixel data supplied from the pre-stage registers
103
-(I−1, J) or the search window row memories
101
-J therein during one clock, respectively. Incidentally, the registers
103
-(7,J) supply pixel data to the pixel comparators
13
-(I, J) of the evaluation unit
4
alone. Namely, pixel data lying in a range of 8 rows and 8 columns moved in the horizontal direction by one pixel for each clock, of pixel data of jth to (j+7)th columns in the frame and lying within the search window are supplied to the evaluation unit
4
.
On the other hand, the coded frame memory 5 allows the registers
12
-(0, 0) through
12
-(7, 7) of the reference register unit
6
to store pixel data in any of the blocks into which the coded frame is divided.
Further, the registers
12
-(0, 0) through
12
-(7, 7) of the reference register unit
6
supply the pixel data thereof to the pixel comparators
13
-(0, 0) through
13
-(7, 7) of the evaluation unit
4
for each clock, respectively.
The pixel comparators
13
-(I, J) of the evaluation unit
4
calculate the differences between the pixel data from the registers
103
-(I, J) of the search window shift register unit
102
and the pixel data from the registers
12
-(I, J) of the reference register unit
6
and supply their differences to the motion vector detection unit
7
.
The motion vector detection unit
7
stores the difference between a position vector in a frame, of a predetermined pixel of a reference block and a position vector of each pixel in the already-coded frame to be compared with the predetermined pixel therein as a search vector together with the sum of the absolute values of their pixel data, which corresponds to an evaluation value.
When, for example, the position in the frame, of a pixel at the upper-left corner of the reference block is given as (m, n) and the position in the frame, of the pixel data supplied to the search window row memory
101
-
0
is given as (m−16, j) through (m+16, j), the search vector changes from (−16, j−n) to (+16, j−n).
Thus, the pixel data in the range of 8 rows and 8 columns, of the pixel data whose positions in the frame are given as (m−16, j) through (m+16, j+7), which pixel data being included in the pixel data in the already-coded frame, are compared with pixel data which constitute each block given by (m, n) through (m+7, n+7). Further, the above-described processing is performed on a range of (n−8)th to (n−1)th rows, a range of (n−7)th to nth rows, . . . , a range of (n+8)th to (n+15)th rows in the already-coded frame. Thereafter, the motion vector detection unit
7
outputs a search vector at the time that the aforementioned evaluation value is minimum, to unillustrated devices or circuits or the like as a motion vector.
Incidentally, an apparatus described in JP-A No. 9-298751 and the like are known as ones related to the present invention. However, they do not disclose the feature of the invention of the present application.
Thus, the motion vector detecting apparatus according to the conventional example 1 has a problem in that since the range to be compared with the reference block is shifted in either one of the horizontal and vertical directions so as to search all the ranges in the search window in order to detect the motion vector, a long time is required till the detection of th
Le Vu
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
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