JPEG Patent Challenged

ChocLinux writes "The Public Patent Foundation has filed a request at the US Patent Office to revoke Compression Labs' data compression patent, which it is reportedly using to harrass anyone that implements the JPEG format. 'CLI's aggressive assertion of the '672 patent is causing substantial public harm by threatening this international standard on which the public relies,' says Pubpat in its filing."

Comments

Covered at Groklaw

[bstadil]

This is covered in details over at Groklaw

Was it obvious?

[swthomas55]

While many software patents are "patently" invalid because of obvious prior art, this one was not obvious to me at the time. Although, I was working in a related field (computer graphics), and not directly in data compression. I had colleagues who were in signal processing (and DCT is at base a signal processing application), and none of them said "oh, that's obvious".

If you read the pubpatent filing, their main point is that an earlier patent, issued to the same company, is prior art for all the points in the '672' patent. The earlier patent was filed more than a year (plus one month) prior to the filing of the '672' patent, which makes it legally prior art.

Anyway, the sucker has less than a year to run, as it was filed in October, 1986. Probably why the lampreys at Forgent are pushing so aggressively. It'll only be a cash cow for another 11 months.

Interestingly, I could have been a target of Unisys, except they couldn't have gotten much blood from this stone. I was the original author of the "compress" program, which turned into an early "open source" effort (although the term hadn't been invented at the time). Compress was an implementation of LZW, based on Welch's 1984 paper in Computer. Only later was I informed that it was patented. After it had been incorporated into Berkeley Unix releases and into the GIF format. I was happy when that patent finally expired, but I had absolutely no doubt of its legitimacy.

As for the claimed superiority of PNG over JPEG, I'd say it depends on the application. JPEG was designed precisely and specifically for the purpose of compressing photographic images. Such images

• Do not compress well using techniques like LZW and Huffman coding
• Have intrinsic variation in pixel values due to noise in the recording process
• Don't have precisely straight and sharp edges

These characteristics make them poorly suited to lossless compression techniques, and also mean that a lossy technique will not degrade the image further than the original noisy recording method did. (Unless you turn up the loss level too high.)

Because of the "if you have a hammer, every problem looks like a nail" principle, people have used JPEG in applications that it's not suited for -- applications where the lossy compression DOES degrade the image quality, and where a different method (LZW, for example) would in fact give a smaller file. Then other people point at these examples and say "PNG (or GIF) is better than JPEG!" My toolbox has hammers, screwdrivers, wrenches, etc. I try to pick the appropriate tool, and don't hammer with a wrench, for example. The same should be true of our computer tools.