ZR36050 datasheet(2/52 Pages) ETC

2 / 52 page

ZR36050

ADVANCE INFORMATION

In addition to the JPEG Baseline, the ZR36050 supports a

subset of JPEG Lossless standard. The ZR36050 performs one

dimensional differential prediction followed by variable-length

encoding for JPEG Lossless compression, and the correspond-

ing inverse operations for JPEG Lossless expansion.

The ZR36050 maintains full compatibility with the JPEG

Baseline standard. The unique ability to perform bit rate control.

Bit rate control capability allows the user to preset the size of a

compressed image file. This capability is important because

without bit rate control, the size of a compressed image is highly

data dependent for a given set of quantization tables (images

with fine detail generate considerably larger files than files gen-

erated from smooth images).

The ability to perform bit rate control is critical for applications

where predictable file sizes for compressed images is desired, or

where the time allocated to transmit an image across a commu-

nications network is fixed. The compressed image file size is

constrained to be no greater than a user specified target, and is

typically kept within a range of 95% to 100% of this target. The

bit rate control feature relies on a two pass algorithm for its

operation.

The ZR36050 has the ability to generate a “thumbnail” version of

an image for “Fast Preview.” This thumbnail image is a 1/64

scale version of the image, and is generated up to 25 times

faster than full image expansion. The thumbnail image is gener-

ated from the JPEG Baseline compressed data, and eliminates

the need for a separately encoded and stored thumbnail image.

This feature is particularly useful for previewing large databases

of images.

The ZR36050 operates as a dedicated processor requiring only

minimal host intervention. The host processor controls the oper-

ation of the device by writing parameter values into the

ZR36050’s Internal Memory. Once initialized, the ZR36050

operates continuously until it has completed the compression or

expansion of the image. Since the ZR36050 fully complies with

the JPEG Baseline standard, the compressed data bit-stream

generally requires no intervention by the host. Full JPEG capa-

bility also allows for the interchange of files created by other

JPEG imaging systems with files generated by systems using

the ZR36050.

The ZR36050 is useful for a wide range of motion and still video appli-

cations. For example, a typical multimedia application (30 seconds of

video at 10 frames/sec and 320 x 240 resolution) would require 69

Mbytes of storage in uncompressed form. With compression using the

ZR36050, the requirement can be reduced to 2.9 Mbytes, making

storage feasible on a personal computer hard disk. Similarly, for digital

still camera applications, the memory requirement can be reduced

from a 22 Mbyte hard disk to a 1 Mbyte memory card for storage of

twenty 768 x 480 compressed images.

The ZR36050 is fabricated with an advanced low-power CMOS

technology, making it suitable for use in low-power, cost-sensi-

tive applications. The device is available in a 100-pin Plastic

Quad Flat Pack (PQFP).

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