Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-04-24
2001-09-11
Lee, Richard (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240240
Reexamination Certificate
active
06289049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vector coding, and more particularly, to a method for coding a motion vector in a moving picture.
2. Background of the Related Art
An outline of an emerging Moving Picture Expert Group (MPEG) standardization MPEG-4 will now be described. The MPEG-4 pursues a technique different from the techniques of MPEG-1 and MPEG-2 previously used to cope with the current trend in which boundaries of techniques of communication, computer and broadcasting are removed and transformed into multimedia. That is, the object of MPEG-4 is a comprehensive technique that embraces each field of the above techniques and their independent technical innovations independently as well as the exploration of fields to which the new comprehensive technique is applicable. The directions that MPEG-4 pursues at large is a technique that allows an Audio and Video (AV) coding at an extra low bit rate.
To realize the technique that allows an AV coding at an extra low bit rate, the following techniques are suggested. First, a new coding technique in which the MPEG-1 and MPEG-2 DCT transform technique is not used, for example, the Wavelet coding system that has less distortion at block boundaries and a high coding efficiency. Second, a technique that conducts motion compensation in a manner other than the MPEG-1 and MPEG-2 block based motion compensation, which conducts the motion compensation by a macro block unit. Third, a region based coding technique inclusive of the contour coding technique and the object oriented coding technique. Fourth, a Fractal coding technique that can make a compression ratio over 1/1000.
Further, there are 8 new techniques that are not yet realized but are trying to be fully realized in MPEG-4. The eight new techniques include improvement of a coding efficiency, scaleability matching to a content, content handling and bit stream editing, improvement of tolerance for error, access to a multimedia data base, coding of a plurality of synchronous data, hybrid coding of natural data and synthesized data, and improvement of a random accessibility at an extra low bit rate.
A related art method for coding a motion vector will be explained with reference to
FIGS. 1-3
.
FIG. 1
shows a motion vector bound of 8×8 motion vectors at an 8×8 mode macroblock.
FIGS. 2
a-
2
d
illustrate definitions of candidate predictors for motion vectors in 8×8 mode macroblock.
FIG. 3
illustrates an example of the case when a predicted motion vector median value lies outside of a bound.
In the emerging MPEG-4 standard, the 8×8 block search operation for integer pixel motion estimation is conducted within ±2 pixel search window centered on a 16×16 motion vector. Therefore, if a particular macroblock is searched in the 8×8 mode, all the motion vectors for 4 blocks in the macroblock will lie within a bound. The matrix shown in
FIG. 1
shows the bound within which the 4 block motion vectors in the macroblock searched in the 8×8 mode can exist. This bound for the 4 motion vectors serves to improve a coding efficiency of motion vectors. Each of the motion vectors representing the 4 blocks in the bound is estimated as median values of neighboring three motion vector candidates, and the x and y components of the difference between the true and the estimated motion vectors, MVD
X
and MVD
Y
, are variable-length coded, which is expressed as the following.
Px=
Median(
MV
1
x, MV
2
x, MV
3
x
),
Py=
Median(
MV
1
y, MV
2
y, MV
3
y
),
and
MVDx=MVx−Px, MVDy=MVy−Py.
FIGS. 2
a-
2
d
illustrate motion vector candidates in a 8×8 mode according to an algorithm for estimation of a motion vector in MPEG-4. However, the motion vector estimation bound shown in
FIG. 1
can not support an MPEG-4 Verification Model (VM) for the following reasons.
Referring to
FIGS. 2
a-
2
d
, when the motion vector prediction candidates in the 8×8 mode macroblock are reviewed, cases exist when the motion vector prediction candidates of which median values are used for estimation of motion vectors lie outside of the bound of motion vectors in a 8×8 mode. Only the case of MV
2
of block
2
is outside the bound of motion vectors in a 8×8 mode if the case of block
1
is excluded. As shown in
FIG. 2
b
, only one of the three motion vector prediction candidates lies within the 8×8 mode macroblock. In this case, an absolute value of the MVD
2
obtained from the predicted value of the median values may lie outside of a bound of 5.0. As shown in
FIG. 3
, when an MV of block
2
is denoted as MV
CurrentBlock
(a motion vector for respective block), an MV
1
of block
2
is denoted as Mv
insideMBprediction
(a motion vector estimation within the bound), and a Median(MV
1
, MV
2
, MV
3
) of block
2
is denoted as MV
MedianPrediction
, there is a case when the MV
MedianPrediction
lies on a point outside of the bound.
Therefore, the related art method for coding a motion vector has various disadvantages. The related art method for coding a motion vector in a moving picture has a problem of bit loss when an estimated value from medians lies outside of a bound.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for coding a motion vector in a moving picture that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Another object of the present invention is to provide a method for coding a vector that prevents an increase in bit rate when a predicted vector lies outside a bound.
A further object of the present invention is to provide a method for coding a moving vector in a motion picture that reduces the bit rate.
A still further object of the present invention is to provide a method for coding a moving vector that reduces bit loss.
To achieve these and other advantages in whole or in parts and in accordance with the purpose of the present invention, as embodied and broadly described, a method for coding a motion vector in a moving picture includes searching a first, a second and a third motion vector prediction candidates for a block
1
among 4 8×8 blocks in a macroblock when a search mode for the macroblock is selected to be an 8×8 mode, searching a first, a second and a third motion vector prediction candidates MV
1
, MV
2
and MV
3
for each of block
1
, block
2
, block
3
and block
4
in succession, comparing a notion vector median prediction value MV
MedianPrediction
for the block
1
to a motion vector bound, determining the motion vector median prediction value as a predicted value for coding the block
1
if the motion vector median prediction value lies within the bound, determining a vector value that lies within the bound of a motion vector prediction candidate among the first, the second and the third motion vector prediction candidates or a motion vector median prediction value as a predicted value PMV for coding the block
1
if the motion vector median prediction value does not lie within the bound, and repeating the step of comparing a motion vector median prediction value to a motion vector bound and determining a predicted value for the entire 8×8 blocks in the macroblock.
To further achieve these and other advantages in whole or in parts and in accordance with the purpose of the present invention, as embodied and broadly described, a method for coding a motion vector includes selecting a motion vector median prediction value for a current block of the plurality of blocks in a macroblock to be a predicted value if the motion vector median prediction value lies within a bound, selecting one of a vector value of a motion vector prediction candidate that lies within the motion vector from the plurality of motion vector prediction candidates for the current block and the motion vector median prediction value to be the predicted value and performing the selecting steps for said each of the plurality of blocks.
Additional advantages, obje
Kim Hyun Mun
Kim Sung Deuk
Lee Young Su
Ra Jong Beom
Fleshner & Kim LLP
Lee Richard
LG Electronics Inc.
LandOfFree
Method for coding motion vector in moving picture does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for coding motion vector in moving picture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for coding motion vector in moving picture will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2534802