Browse Prior Art Database

GUARANTEED DATA COMPRESSION

IP.com Disclosure Number: IPCOM000025072D
Original Publication Date: 1983-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 153K

Publishing Venue

Xerox Disclosure Journal

Abstract

There is described herein techniques intended to guarantee certain minimum compression ratios for scanned images in the range of 2:l to 9:l whatever the type of original image. Such a guarantee is useful to reduce the maximum data rate and data storage capacity that will be required of the external data storage devices and electronic equipment.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 58% of the total text.

Page 1 of 4

GUARANTEED DATA COMPRESSION Ronald G. Matteson
To Russell Hsing

Proposed Classification
U.S. CI. 358/261 Int. CI. H04n 1/00

"8

OVERFLOW

-D DETECT

-7 9

rf

SELECT

No'SE

FILTER

I A A

(BINARY)

480SPI 10 /2 //

-PREDICT +

COMPRESS 8SCAN LINE 2:1

BUFF (COMPR) --+

CCITT

LINE COPY r(j

,,

vf

4

1/2-2/3 'IT/

LPF LINE FILTER, -

I I THROWAWAY I PREDICT^

THROWAWAY

BUFF SIZE

8K 8K

LINE COPY GUARANTEED COMPRESSION (2 : 1-9 * I)

' COMPRESS 8 SCAN-LINE

r,

,-,

,

CC ITT

BUFF4 (COMPR)

Volume 8 Number 3 !May/June 1983

275

[This page contains 1 picture or other non-text object]

Page 2 of 4

GUARANTEED DATA COMPRESSION (Cont'd)

/4 -

LPF X (BINARY) - 12 17

d l

X -

There is described herein techniques intended to guarantee certain minimum compression ratios for scanned images in the range of 2:l to 9:l whatever the type of original image. Such a guarantee is useful to reduce the maximum data rate and data storage capacity that will be required of the external data storage devices and electronic equipment.

CON% TONE/ Y

/6 HALF TONE LPF

 * INPUT 480 SPI

 CONT. TONE/HALF TONE GUARANTEED COMPRESSlON

(2 : I- 9 : I)

t-

+ SCREEN

THROWAWAY

A

1 I

C.R. X Y SCREEN CPI

2:l I 6 x 6 85 2: I '/2 I 6x6 85 4:l '/2 '/2 6x6 56 6:l v3 '/2 5x 5 56 6:l '/2 v3 5x5 56 9:l 1/3 '/3 5x5 45

i

Experimental work has indicated that compression ratios of between one and two are all that can be expected from various standard compression algorithms for halftone and continuous tone images. For line copy, however, there is an opportunity to achieve ratios in the region of 2:l to 9:l without degrading image quality perceptibly and the techniques disclosed herein are designed to guarantee such data compression with a minimum of unsatisfactory image degradation.

Number 8 Volume XEROX 276 DISCLOSURE JOURNAL

3 May/June 1983

[This page contains 1 picture or other non-text object]

Page 3 of 4

GUARANTEED DATA COMPRESSION (Cont'd)

The approach includes noise filtering, predictive coding, standard compression algorithms, data buffering, and circuitry for selecting different compression algorithms. In Figure 1, the binary line copy data input to the system flows along either channel 5 or channel 6, with channel 5 normally being preferred for use whenever adequate compression is achieved. An eight scanline buffer 7 stores the compressed data until the end of the 8 scanline compression block at which time the block of stored data is output and the next block started. If the expected compression ratio is achieved (for example, 4:1), and using a 12K buffer size, the data will be processed through the channel 5. If the buffer 7 overflows before the end of the compression block, indicating that the hoped for compression ratio is not being achieved, then the overflow detect circuitry 8 actuates 2:l selector 9 to switch over to the data channel 6. In channel 6, th...