Data compression... Anyone?

[Joachim P. Dyndale]

I'm very interested in data compression, and I've been looking around for a good web site that explains various compression algorithms and encoding algorithms in a down-to-earth way, without complex mathematical formulas. Anyone know of any good sites like this? Or any good books perhaps? I'm greatly looking forward to testing the app that DJDM's company is releasing soon. Better compression than mpeg4 but totally non-lossy! WOW!

[Ethan Winer]

Joachim, > ... explains various compression algorithms and encoding algorithms in a down-to-earth way, without complex mathematical formulas. < The simple explanation is that lossy compression programs look for program content that is too soft to be important, and remove them to save space. --Ethan

[Anderton]

Another way to look at it is like this: Suppose you have a 16-bit signal. Now suppose most of the content is in the top 24 dB of the range (as is typical with pop music). So, that's about 4 bits of resolution. If you encode only those four bits, you've cut your data rate to 25% of what it had been. What about the other 12 bits? You theoretically wouldn't hear them anyway, because they would be masked by the louder parts. But also remember that in most cases, "data compression" is a misnomer. "Data omission" is technically closer to the truth.

[Paul Berolzheimer]

What these guys are talking about is a theary called, if I remember correctly, Perceptive Coding, which states that the average listener won't hear something 30 dB or so below something else happening at the same frequency. Compression algorythms like MP3 then just throw away material that falls into that category. the problem is that there's a big difference between "average" and "most" or "all". just listen to how the reverb tails or crash cymbals disappear as soon as a new, louder sound comes in and you'll see that the basic premise is wrong.

[Joachim P. Dyndale]

Thanks... I know a little bit about compression, but I know very little math (I'm going to do something about that next year). I'm mainly interested in lossless compression, and not only audio. Though, audio is, of course, very interesting as well. I know that compression is HIHGLY related to advanced math, so I might be searching for something that doesn't exist... I need an article that shows the principles behind different types of algorithms in plain english, without complex math formulas. But still, thanks. That part about audio compression was interesting.

[philbo_Tangent]

[quote]Originally posted by Joachim P. Dyndale: [b]I'm very interested in data compression, and I've been looking around for a good web site that explains various compression algorithms and encoding algorithms in a down-to-earth way, without complex mathematical formulas. Anyone know of any good sites like this? Or any good books perhaps? I'm greatly looking forward to testing the app that DJDM's company is releasing soon. Better compression than mpeg4 but totally non-lossy! WOW![/b][/quote]For LOSSLESS compression, here is a place to start: http://datacompression.info/

[Joachim P. Dyndale]

Thanks, a very informative site indeed... DJDM: How's that codec coming?

[Joachim P. Dyndale]

Bump. (For DJDM...)