Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-10-30
2001-12-18
Le, Vu (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240160, C348S699000
Reexamination Certificate
active
06332002
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a coding technique of a digital image, and more particularly to a motion prediction apparatus and method which is capable of reducing a calculation amount required in a single-pixel and half-pixel motion prediction process as well as an input and output band width when a motion is predicted by employing a hierarchical block matching algorithm.
2. Description of the Related Art
There has been required an information compressing method so as to process a large quantity of information resulting from a tendency of multimedia in the recent communication media. Accordingly, various information compressing technique has been developed. The typical information compressing method includes the MPEG(Moving Picture Experts Group)-2 which is an international standard of the moving picture compressing method.
Generally, the macro block is a basic unit for performing a signal compression in a coder of MPEG-2 system. One macro block consists of a brightness signal(Y) block having 16×16 pixels and a color-difference signal(Cr and Cb) block having 8×8 pixels.
The first step for the image compression is extracting the macro block from a certain input image. To this end, there is required three operations of the color space conversion, the chrominance component decimation and the block partitioning. The color space conversion is an operation for transform the input image into Y, Cr and Cb space so as to reduce the redundancy of red(R), green(G) and blue(B) input from a camera to be converted into a digital shape. The color-difference signal decimation refers to decimating the color-difference signals Cr and Cb in the horizontal and vertical direction because the brightness signal Y representing the contrast of image has such a wide frequency band that it is well recognized visually, whereas the recognition factor in the color-difference signal Cr or Cb representing colors is lower than that in the brightness signal Y. For example, in the case of a format image having a ratio of 4:2:0, the respective decimation factors become a ratio of 2:1. The block partitioning is to divide Y, Cb and Cr images obtained through the color space conversion and the chrominance component decimation mentioned above into sizes suitable for coding them. For example, the brightness signal Y is divided into a 16×16 pixel unit, and each color-difference signal Cr and Cb is divided into a 16×16 pixel unit.
The second step for the image compression is to provide a motion prediction and a compensation for the macro blocks extracted from the entire image regularly. Such motion prediction and compensation are intended to compress an image effectively by omitting a redundant coding process for the adjacent video image in the time base. The conventional motion prediction and compensation process will be explained with reference to a coder of MPEG-2 system shown in
FIG. 1
below.
FIG. 1
is a block diagram showing a typical coder of MPEG-2. In
FIG. 2
, the MPEG-2 system coder includes a frame memory
2
connected to an input line
1
, a frame delay
18
for storing a decoded image, and a motion estimator
20
connected commonly to the input line
1
, the frame memory
2
and the frame delay
18
to perform an operation for predicting and compensating for a motion of an input image.
In the coder shown in
FIG. 1
, the frame memory
2
serves to store an image received over the input line
1
in the frame unit. The motion estimator
20
predicts and compensates a motion of the input image. To this end, the motion estimator
20
is comprised of a first motion estimator
22
connected to the input line
1
and the frame memory
2
commonly, a second motion estimator
24
connected to the input line, the first motion estimator
22
and the frame delay
18
, and a motion compensator
26
connected to the second motion estimator
24
and the frame delay
18
. The first motion estimator
22
detects a position of the most analogous block to the previous image stored in the frame memory
2
with respect to the brightness signal(Y) block in a certain macro block from the image signal received over the input line
1
. The detected block position is employed as a reference position for the second motion estimator
24
. The second motion estimator
24
receives the input image inputted over the input line
1
and a reconstructed image stored in the frame delay
18
to detect the most analogous block to the brightness signal(Y) block in the macro block with respect to a reference position inputted from the first motion estimator
22
from the reconstructed image. Then, the MPEG-2 system coder transfers the detected position to a decoder, so that the decoder can obtain an image identical to the reconstructed image referred in the coder on a basis of the received position information. The motion compensator
26
extracts the most analogous block to the macro block from the reconstructed image stored in the frame delay
18
on a basis of the final position information generated at the second motion estimator
24
.
The MPEG-2 system coder further includes a subtractor
4
connected commonly to the frame memory
2
and the motion compensator
26
to generate a difference image between the previous image and the estimated reconstructed image, a coder
34
connected to the subtractor
4
to code the difference image, a decoder
36
connected to the coder
34
to reconstruct the coded difference image, and an adder
16
connected to the decoder
36
and the image compensator
26
to add the reconstructed difference image and the estimated image and output the added image to the frame delay
18
. Moreover, The MPEG-2 system coder includes a variable length coder(VCL) and a buffer
32
that are connected, in series, to the coder
34
, and a bit rate controller
10
for controlling a bit generation rate by adjusting quantizing step sizes Qp of a quantizer
8
and a dequantizer
12
with reference to the characteristic of the input image stored in the frame memory
2
and the data quantities of the buffer
32
.
In such a configuration, the subtractor
4
generates a difference image between a macro block of the previous image stored in the frame memory
2
and a macro block of the estimated reconstructed image from the motion compensator
26
and outputs the difference image to the coder
34
. In other words, the subtractor
4
outputs a difference image in which a redundancy between images adjacent to each other in the time base is eliminated. The coder
34
carries out the discrete cosine transform(DCT) processing for the difference image inputted from the subtractor
4
to code the difference image, thereby eliminating the space area co-relationship existing in the difference image. To this end, the coder
34
further includes a DCT circuit
6
for carrying out a DCT operation of the difference image in an 8×8 pixel unit, and a quantizer
8
for quantizing the DCT transformed signal. The VCL
30
is connected to the quantizer
8
to compress and output the coded difference image again in accordance with a value of code generation probability. The buffer
32
is connected to the VCL
30
to output a bit stream of the difference image in the first-in first-out system. The decoder
36
connected to the quantizer
8
reconstructs the coded difference image by carrying out an operation similar to the image reconstruction process performed at the coder. To this end, the decoder
36
includes an inverse quantizer
12
connected, in series, to the quantizer
8
to inverse-quantize the coded difference image, and an inverse discrete cosine transform(IDCT) circuit
14
for reconstructing the difference image by carrying out the IDCT operation. The adder
16
adds the difference image reconstructed at the IDCT circuit
14
to the estimated image from the motion compensator
26
and outputs the added image to the frame delay
18
. Accordingly, the frame delay
18
stores a new reconstructed image for estimating an image to be inputted in the next order
Lee Hee Sub
Lim Kyoung Won
Fleshner & Kim LLP
Le Vu
LG Electronics Inc.
LandOfFree
Motion prediction apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motion prediction apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motion prediction apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587434