Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
1998-05-20
2001-01-09
Mancuso, Joseph (Department: 2723)
Image analysis
Image compression or coding
Adaptive coding
C348S404100
Reexamination Certificate
active
06173079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a buffer data control circuit and method. More particularly, the present invention relates to a circuit and method which controls the amount of image compression data, which is processed in an image compression system using wavelet transform, accumulated in a channel buffer.
2. Background Art
In general, image compression is performed for the purpose of reducing the bit rate of input image data for its transmission, or improving the efficiency of a storage for storing the image data. A conventional image compression system using a discrete wavelet transform is shown in FIG.
1
. Referring to
FIG. 1
, a discrete wavelet transformer
10
wavelet-transforms an input digital image applied thereto, and outputs a wavelet signal having a configuration which is shown in
FIG. 3. A
vector assembly
20
receives the wavelet signal, and generates a wavelet signal having a DC coefficient and wavelet signal having an AC coefficient.
A differential pulse code modulator
30
differential-pulse-code-modulates the wavelet signal having a DC coefficient, to convert it into a differential wavelet signal, and supplies this differential wavelet signal to a scalar quantizer
40
. Scalar quantizer
40
scalar-quantizes the differential wavelet signal, and supplies it to a Huffman encoder
50
. Huffman encoder
50
encodes the scalar-quantized differential wavelet signal, converts it into a DC compression signal, and supplies the DC compression signal to one input terminal of a multiplexer
80
.
A vector quantizer
60
receives the wavelet signal having an AC coefficient from vector assembly
20
, vector-quantizes it, and supplies the vector-quantized wavelet signal to another Huffman encoder
70
. Huffman encoder
70
encodes the vector-quantized wavelet signal having AC coefficient, converts it into an AC compression signal, and supplies this AC compression signal to the other input terminal of multiplexer
80
. Multiplexer
80
transmits the AC compression signal and DC compression signal to a network through a channel, according to a selection signal supplied by a system controller (not shown).
When a 30 frames/sec color image in quadrature common intermediate format is compressed at 55:1 in the above-described image compression system using wavelet transform, the number of bit transmitted through the channel for one second equals 30∂e 188∂e 144∂e8∂e2∂e2∂e (1/55)≈472,529.4 bits/sec. When motion estimation is added to the compression system in the direction of reducing the temporal redundancy of a motion picture, using full search algorithm, to obtain five-fold compression effect, the number of bits transmitted per one second becomes 94,505.9 bits/sec. However, this value, 94,505.9 bits/sec, is relatively large when compared to the channel capacity of 28.8 kbits/sec currently available for transmitting data through the public switched telephone network (PSTN) by means of a modem. Accordingly, in order to transmit image data of this bit rate through a modem, it is required that either the number of transmission frames per second be reduced, or the source data of the digital image be compressed at higher compression factor which invariably results in a deterioration in the picture quality.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a circuit and method, which controls the amount of image compression data, which is processed in an image compression system using wavelet transform, accumulated in a channel buffer by removing data in a frequency band to which human eyes are less sensitive, from the wavelet-transformed image data, according to a reference value.
To achieve this object, a buffer data control circuit is provided in an image compression system using a wavelet transform. The buffer data control circuit includes a buffer for storing, for a predetermined time, compressed image data to be transmitted to a channel, as well as a buffer controller. The buffer controller has a data reference value, which is for integrating the input speed of the compressed image data input to the buffer over a predetermined period, and adding the integration value to the amount of data accumulated in the buffer at a specific time, to thereby estimate the amount of data to be accumulated for the next period. The buffer controller compares the amount of data to be accumulated for the next period with the data reference value, and generates a processing signal. The starting point of the predetermined period corresponds to the specific time. The buffer data control circuit also includes a vector assembly for removing data having high-frequency diagonal component from data forming the frame structure of a wavelet transformed image, according to the processing signal.
The present invention has broad applicability in image compression systems in general.
REFERENCES:
patent: 5420636 (1995-05-01), Kojima
patent: 5546477 (1996-08-01), Knowles et al.
patent: 6023296 (2000-02-01), Lee et al.
patent: 411112984 (1999-04-01), None
Cooperrider F. E.
Mancuso Joseph
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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