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ZR36050

JPEG IMAGE COMPRESSION PROCESSOR

Zoran Corporation 

ADVANCE INFORMATION

ZR36050

In JPEG Baseline compression, the Encoding Unit reads the

DCT coefficients from the Block Buffers in the JPEG zig-zag

sequence and quantizes them using the tables in the Quantiza-

tion Table Store. The Quantization Table Store holds up to four

quantization tables. Each component of the image is assigned

one of the quantization tables; this assignment is specified in the

JPEG frame header.

The Encoding Unit encodes the difference of the quantized DC

coefficients of the current and previous blocks, using one of the

DC tables in the Huffman Table Store. After accumulating runs

of zero-valued AC coefficients, it encodes the zero run lengths

and the non-zero AC coefficients using the AC tables in the

Huffman Table Store. The Huffman Table Store has space for

two DC Huffman tables and two AC Huffman tables. Each com-

ponent of a scan is assigned to one DC table and one AC table;

this assignment is specified in the JPEG scan header.

Quantization tables are not used in Lossless compression. In

this mode of operation, the Encoding Unit performs one-dimen-

sional, horizontal predictive coding and Huffman coding of the

samples, similar to that of the DC coefficients in Baseline

compression.

When it has generated a Huffman code, or when it is transferring

the marker segment data, the Encoding Unit writes the com-

pressed data into the Code Buffer. From there, the compressed

data is transferred out of the device, either via the Compressed

Data Interface, or via the Host Interface.

The procedure for JPEG Baseline or Lossless image expansion

is the inverse of the corresponding compression procedure

When expanding an image, the Encoding/Decoding Unit detects

and decodes all the markers and marker segment parameters

included in the compressed data. The host does not need to

extract or decode parameters, such as tables, from the JPEG

compressed data file, since this is done automatically.

Compressed Data Interface

The Compressed Data Interface is the fastest means of transfer-

ring the compressed data into or out of the ZR36050, therefore

it could be used in a motion video compression application,

(Refer to the example shown in Figure 3). Since it can optionally

be configured to operate with up to seven internally generated

wait states, it is also suitable for use with a slow compressed

data store, such as a memory card. When the Compressed Data

Interface is being used, it transfers data in a Master mode,

driving the access control signals to an external auto-increment-

ing (e.g. FIFO) memory device.

Host Interface

If the ZR36050 is configured to transfer the compressed data via

the Host Interface, it can do so in one of two submodes. Slave or

DMA modes. The principal function of the Host Interface is to

allow the host to access the Internal Memory. This access is

required in order to program the operating mode of the device,

specify the JPEG marker segments and their parameters for

compression, initiate the encoding or decoding operation and

read the status of the device.

Internal Memory

The Internal Memory is partitioned into a Control Registers

Section and a JPEG Marker Segments Section.

The Control Registers Section contains the various configuration

registers, status registers for interaction with the host, and infor-

mational registers that provide feedback to the host after the

completion of an operation by the ZR36050.

The Marker Segments Section is where the host writes the

contents of the JPEG marker segments before initiating com-

pression of an image or changing markers between the frame

and scan marker, or between scans. After an expansion, it

Composite

Video Source

A/D

Y

Digital

Composite U

Video

Decoder

V

Strip Buffer,

Raster to Block

Converter

PIXEL

DSYNC

STOP

EOS

ZR36050

JPEG Image Processor

CODE

CWE

COE

CCS

Compressed

Data FIFO

Display

R

Triple D/A

G & YUV to

B

RGB

Y

U Display

Controller

V

Data

Interface to Computer Peripheral Bus

SYNC

Figure 3. Typical Motion JPEG Compression/Expansion System Configuration

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