ZR36050 Просмотр технического описания (PDF) - Zoran Corporation

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ZR36050

JPEG IMAGE COMPRESSION PROCESSOR

Zoran Corporation 

ADVANCE INFORMATION

ZR36050

CLK_IN

CBUSY

CCS

CWE

CAEN

CODE

Figure 16. Master Mode Compressed Data Write in Encoding, Shown for Bus Cycle Time of Two CLK_IN

Pixel Interface

The pixel interface operates synchronously in all modes of oper-

ation, transferring an image data sample in or out every CLK_IN,

when enabled to do so. The DSYNC and STOP signals control

the flow of data on the PIXEL bus, DSYNC indicating which clock

cycles contain valid data, and STOP acting as a request to halt

data transfer for an arbitrary time interval. An additional signal,

EOS, indicates the end of a scan. In encoding modes, PIXEL,

DSYNC and EOS are inputs and STOP is an output, whereas in

decoding modes, PIXEL, DSYNC and EOS are outputs and

STOP is an input.

In the JPEG Baseline encoding and decoding modes, image

data is transferred on the PIXEL bus a block at a time, and

DSYNC indicates the beginning of a block. DSYNC is active for

one CLK_IN cycle, preceding the first sample of a block, and is

always followed by a burst of 64 image samples.

In the Fast Preview decoding mode, and in JPEG Lossless

encoding and decoding, where image data is transferred in a line

by line raster, DSYNC is active in the CLK_IN cycle preceding

each sample.

JPEG Baseline Encoding

In JPEG Baseline encoding, the Pixel Interface samples the

most significant eight bits of the PIXEL bus.

Figure 17 shows two consecutive blocks of image samples

being input at the beginning of a scan, or after a break in data

transfer. Note that the figure shows the second block immediate-

ly following the first, however, this is not necessarily the case.

The first sample of the second block could be separated from the

last sample of the first block by any number of clocks, by

delaying the activation of DSYNC.

CLK_IN

DSYNC

PIXEL

0

1

2

62

63

0

1

2

FIRST BLOCK

SECOND BLOCK

Figure 17. Beginning of a Scan in JPEG Baseline Encoding

22

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