CNET también está disponible en español.

Ir a español

Don't show this again


Commentary: No miracles, just trade-offs

"Lossless" compression--the kind used for data files--is limited by the need to perfectly restore every bit of data.

By Martin Reynolds, Gartner analyst

"Lossless" compression--the kind used for data files--is limited by the need to perfectly restore every bit of data.

See news story:
The quest for near-perfect compression
Pure data files that do not contain random or previously compressed data, such as images and sounds, will shrink in size by 50 percent to 80 percent, depending on the content. Once a file is compressed, it is extraordinarily difficult to compress it further.

For images and sounds, not all of the data is required to re-create the content for human consumption. Therefore, compression algorithms not only compress the data, but also discard information that is not necessary to re-create a substantial copy of the original. The most common examples of this technique are MP3 audio files, DVD video systems and DirecTV video systems--which use MPEG-2 encoding. With "lossy" compression techniques, these systems produce data streams 10 percent smaller than the original--with nearly undetectable loss in quality.

The DivX motion video encoder, the latest entry into the compression stakes, can collapse entire DVD movies onto a single CD--about a 100-to-1 compression ratio compared with the original material. The quality is good considering the compact file size. This technology will give movie companies ongoing grief as they try to clamp down on piracy.

What's going on at ZeoSync is unclear. CEO Peter St. George's claims could lead one to believe that his company is delivering lossless compression at ratios dramatically better than today's compression technology--which would be a modern-day miracle. But don't count on this technology saving networks and storage from large files.

On the other hand, video seems to have some mileage left in it for lossless compression. Audio, thanks to the driving engine of cellular phone technology, is already down to less than 10 kilobits per second for acceptable quality.

Therefore, two conclusions are possible about ZeoSync. One is that the company is promising a technology that would deliver incredible benefits to the IT industry--if that technology existed, which may not be true. The other is that the company has found a way to improve lossy compression of video and audio files. If that is the case, it faces fierce competition from established standards.

ZeoSync may have some worthwhile technology that, over time, will become mainstream. However, the field is strong enough that competing technologies represent a significant obstacle.

Gartner is, at the moment, skeptical that ZeoSync will have a material impact on the industry.

(For a related commentary on MPEG-4 compression technology, see

Entire contents, Copyright © 2002 Gartner, Inc. All rights reserved. The information contained herein represents Gartner's initial commentary and analysis and has been obtained from sources believed to be reliable. Positions taken are subject to change as more information becomes available and further analysis is undertaken. Gartner disclaims all warranties as to the accuracy, completeness or adequacy of the information. Gartner shall have no liability for errors, omissions or inadequacies in the information contained herein or for interpretations thereof.