# US 5,703,799 A · Lossless transform coding system for digital signals

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- Number: US 5,703,799 A
- Document ID: US5703799A
- Status: Granted
- Kind: A
- Application number: 08/668,046
- Filed: 1996-06-17
- Granted: 1997-12-30
- Earliest claimed: 1995-06-16
- Assignees: NEC Corporation
- Inventors: Mutsumi Ohta
- Web page: https://patentgrep.com/patent/US5703799A

## CPC

- G06T 9/007: {Transform coding, e.g. discrete cosine transform}
- G06F 17/147: {Discrete orthonormal transforms, e.g. discrete cosine transform, discrete sine transform, and variations therefrom, e.g. modified discrete cosine transform, integer transforms approximating the discrete cosine transform (G06F17/145 takes precedence)}
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

The invention provides a coding system and a decoding system wherein a discrete cosine transform which provides a high coding efficiency is approximated to allow reversible coding and decoding while maintaining the high coding efficiency and a system which includes such coding and decoding systems. Reversible coding is realized by multiplying a transform matrix by a fixed number for each row to approximate the transform matrix with integer values, performing requantization in a basic region defined by a multiple of a determinant for suppressing redundancy while maintaining a condition wherein reversible coding is possible in the basic region, and performing requantization for the entire region making use of the fact that such basic region appears periodically in a signal space.

## Claims

### Claim 1

A transform coding system for digital signals which performs a four-element discrete cosine transform, comprising:
means for approximating the four-element discrete cosine transform with an integer linear transform represented by a matrix of ##EQU21## and means for performing the four-element discrete cosine transform using the matrix.

### Claim 2

A transform coding system for digital signals which performs an eight-element discrete cosine transform, comprising:
means for approximating the eight-element discrete cosine transform with an integer linear transform represented by a matrix of ##EQU22## and means for performing the eight-element discrete cosine transform using the matrix.

### Claim 3

A transform coding system for digital signals which performs an eight-element discrete cosine transform, comprising:
means for approximating the eight-element discrete cosine transform with an integer linear transform represented by a matrix of ##EQU23## and means for performing the eight-element discrete cosine transform using the matrix.