ZR36050
ADVANCE INFORMATION
JPEG IMAGE COMPRESSION PROCESSOR
FEATURES
■ Implements JPEG Baseline image compression and
■ “Fast Preview” option
expansion, including:
- Preview of “thumbnail” version of images (up to 25x faster)
■ Bit rate control option
- DCT/IDCT operations
- Quantization
- Variable length coding/decoding
- Guarantees compressed image file size
■ Low cost solution
■ Full support of the JPEG Baseline standard, including:
- Low cost single chip
- Support for inexpensive memories
- Requires minimal host intervention
- Bit and byte stuffing
- JPEG markers including restart (RST), application (APP),
and comment (COM)
■ TTL compatible
■ JPEG Lossless compression and expansion
■ DMA/SLAVE bus interface
■ 27 and 21 MSamples/sec data-rate
■ Standby mode for very low power consumption
■ 100-pin plastic quad flat-pack (PQFP) packaging
■ Motion video (30 frames/sec) compression/expansion
capability for CCIR resolution (720 x 480)
APPLICATIONS
■ Computer and multimedia add-in boards
■ Full-motion video compression/expansion
■ Digital still cameras and peripherals
■ Security and industrial systems
■ Videophones and color FAX machines
■ Color printers and scanners
■ Fixed bit rate image transmission devices
■ 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).
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
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.”
12
8
PIXEL
CODE
PIXEL
Interface
DSYNC
EOS
COE
CWE
Compressed
Data Interface
STOP
CCS
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.
CAEN
CBUSY
COMP
RESET
STDBY
FREEZE
END
8
ZR36050
Control
DATA
ADDR
JPEG IMAGE
COMPRESSION
PROCESSOR
10
2
CL
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
CLKEN
RD
WR
11
Host Interface
DCT
Coefficient
Output
COEF
CS
CSYNC
INT
DINT
DREQ
DACK
Clock
CLK_IN
VSS
Figure 1. ZR36050 Logical Pinout
ZORAN Corporation ■ 1705 Wyatt Drive ■ Santa Clara, CA 95054 ■ (408) 986-1314 ■ FAX (408) 986-1240
August 1993
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