This article is now maintained as a Wiki page at http://wiki.multimedia.cx/index.php?title=Mean_Removal.

Mean removal is another one of those concepts– like differential coding– that sounds like it would be difficult to understand. It’s not.

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This article is now expanded and maintained at http://wiki.multimedia.cx/index.php?title=Differential_Coding.

Differential coding explained:

1 + 1 = 2

Got that?

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This page is maintained in Wiki format at http://wiki.multimedia.cx/index.php?title=Run_Length_Encoding

I may as well start this series of articles off with what is perhaps the simplest multimedia compression technique of them all: run length encoding (RLE). The basic idea behind this concept is to encode information about runs of identical numbers rather than encode the numbers themselves.

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A rather alarming fact came to my attention recently: There are people out there on the internet who actually learn everything they know about multimedia technology strictly from the information provided at multimedia.cx.

So I thought maybe I should write some articles about core multimedia concepts. Things like the discrete cosine transform, vector quantization, Huffman coding. The fact is that there are already countless pages out there that cover all of these concepts. What could I add?

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Check out hp’s new blog, Descrambling Eggs With A Blender. hp is an aspiring reverse engineer with a keen interest in multimedia technology. Watch him closely– he’s working on some big things.

Sometimes, multimedia programs are modular which facilitates reverse engineering. But what if they are not modular or are just standalone programs that do one thing well?

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I am getting more ideas in my head about how I want to put this BFRE program together.

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Click on (more) for the solutions to the brief RE puzzles…

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These are a few of my favorite little reverse engineering puzzles to show people when they express interest in the craft. They are also 2 sample functions I thought I would use when prototyping the BFRE program.

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And software companies wonder why we users have trouble taking software end-user license agreements seriously. Roberto Togni actually read the license that accompanies On2′s VP7 Decoder. It contains this clause:

You may NOT:
4.publish or provide any results of tests, including without limitation benchmark tests, run on the Software to any third party without On2′s prior written consent

In fairness to On2, this is not an uncommon clause in EULAs. However, it presents some very curious scenarios. Am I allowed to publish something like this?

I looked at a VP7 sample and it did not look as good as WMV9, H.264, or even On2′s own VP6.

Maybe I should write and ask permission. A colleague brought up another point: Since this “no benchmark tests” is such a common EULA clause, it should stand to reason that Microsoft’s Windows Media Encoder carries the same license. It is extremely unlikely that Microsoft would have granted written permission for this whitepaper exercise.

Update: Again, to be fair, the decoder license (On2′s Truecast Player) does not appear to mention anything about publishing benchmark tests. That is on the limited trial codec license.