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ZR36050

JPEG IMAGE COMPRESSION PROCESSOR

Zoran Corporation 

ZR36050

ADVANCE INFORMATION

JPEG IMAGE COMPRESSION PROCESSOR

FEATURES

s Implements JPEG Baseline image compression and

expansion, including:

- DCT/IDCT operations

- Quantization

- Variable length coding/decoding

s Full support of the JPEG Baseline standard, including:

- Bit and byte stuffing

- JPEG markers including restart (RST), application (APP),

and comment (COM)

s JPEG Lossless compression and expansion

s DMA/SLAVE bus interface

s Motion video (30 frames/sec) compression/expansion

capability for CCIR resolution (720 x 480)

s “Fast Preview” option

- Preview of “thumbnail” version of images (up to 25x faster)

s Bit rate control option

- Guarantees compressed image file size

s Low cost solution

- Low cost single chip

- Support for inexpensive memories

- Requires minimal host intervention

s TTL compatible

s 27 and 21 MSamples/sec data-rate

s Standby mode for very low power consumption

s 100-pin plastic quad flat-pack (PQFP) packaging

APPLICATIONS

s Computer and multimedia add-in boards

s Full-motion video compression/expansion

s Digital still cameras and peripherals

s Security and industrial systems

s Videophones and color FAX machines

s Color printers and scanners

s Fixed bit rate image transmission devices

s Cost-sensitive image compression systems

GENERAL DESCRIPTION

The ZR36050 is a high-speed JPEG Image Compression Pro-

cessor that performs the algorithm specified by the JPEG

Baseline and JPEG Lossless standards for high-quality image

compression and expansion of continuous-tone color or mono-

chrome images. The ZR36050 performs Discrete Cosine

Transform (DCT), quantization and variable-length encoding for

image compression (coding), and the corresponding inverse

operations for expansion (decoding).

In the JPEG Baseline encoding operation, the ZR36050

performs the DCT operation on 8 x 8 blocks of image data, con-

verting image data into its spatial frequency components, and

quantizes them using a user defined “quantization table.”

Because the human visual system is less sensitive at the higher

spatial frequencies, these higher frequency components can be

quantized more coarsely than the lower-frequency components,

with negligible effect on image quality.

The coarser quantization of high-frequency coefficients results in

long strings of zero valued quantized coefficients, when the 8x8

blocks are scanned in zigzag order. The scanned coefficients

are characterized in terms of their nonzero values and the zero

run lengths. As a result, a long string of zeroes is coded as a

single number. The ZR36050 then performs Huffman coding

using user-defined Huffman tables, whereby bit patterns of dif-

ferent lengths code the nonzero values (values that occur

frequently use the shortest codes; while those that infrequently

occur use the longest codes). These techniques greatly reduce

the amount of memory needed to store an image.

In the decoding operation, the compressed data is decoded (the

inverse of the Huffman and the zigzag modified-run-length

coding), and dequantized. A 2-D inverse Discrete Cosine Trans-

form is performed on the DCT coefficients, resulting in an

expanded image.

+5V

PIXEL

Interface

Control

DCT

Coefficient

Output

Clock

12

PIXEL

8

CODE

DSYNC

COE

EOS

CWE

STOP

CCS

COMP

RESET

CAEN

CBUSY

STDBY

FREEZE

ZR36050

END

2 CL

JPEG IMAGE

COMPRESSION

PROCESSOR

CLKEN

11

COEF

8

DATA

10

ADDR

RD

WR

CS

CSYNC

INT

DINT

DREQ

CLK_IN

VSS

DACK

Compressed

Data Interface

Host Interface

Figure 1. ZR36050 Logical Pinout

ZORAN Corporation s 1705 Wyatt Drive s Santa Clara, CA 95054 s (408) 986-1314 s FAX (408) 986-1240

August 1993

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