Hi, guys!

I've been looking for some sort of MP3 decoding spec for some time now, and have stumbled upon the paper "MPEG-Layer 3 Bitstream Syntax and Decoding" hosted at mp3-tech.org, which looks like just the thing I need.

The problem is that the only version I have found has major formatting issues. I've tried opening it up with Word, AbiWord, and OpenOffice, but nothing seems to display it correctly.

None of the images are there, many things are in the wrong places, and all the sections are marked "I", "1", or "a". Does anybody have a version which displays correctly, or was the file bad to begin with?

Thanks.

near the bottom of the file, it says "Microsoft Word 6.0 Document". Perhaps you can force Word to import the document as a specific version.

Well, Word does have a "Word 95 / 6.0" selection, but it looks the same as just letting it autodetect.

I find it odd that this seems to be the only (free) document specifying the MP3 bitstream, and yet it's in such bad shape.

Does anybody have an old version of Word (like 6.0 ) laying around to test out the quality? A zip file containing the doc can be found on this page (not sure if they tolerate hotlinking; it's about 2/3 down the page)


I might just have to stare at a decoder source for hours on end to try to make sense of it. Anybody know a particularly well-documented open decoder?

I tried viewing it on Office XP, had the same issue as you.
When I tried to convert it to another format, it bitched about not enough memory to display the images. o_O

Regarding this doc, I am not aware of a publically available version that is correctly formatted, but I would also be interested by a publically available one.


The book "Understanding MP3" by Martin Ruckert is mostly a description of an encoder (wich is available freely on the web). It is very valuable if you want to fully understand decoding implementations.

IMO that's a good way to do it. I can recommend the following sources:

amp11
-download from mp3-tech.org
-nice and clean C++ code
-no comments to explain anything but the code is quite descriptive
-my personal favourite

MAD
-download from underbit.com
-nice and clean C code
-contains some explanatory comments
-IMO, the fixed point stuff is a bit distracting when you're trying to understand MP3 in general

dist10
-download from mp3-tech.org
-C code released by the ISO MPEG group
-IMO, this rather un-optimized code is a good alternative when you're stuck in another decoder's "super-special-optimized" routines

When I wrote an MPEG audio decoder a few years ago, I printed the relevant parts of several different decoder sources and pinned them on the wall beside my computer desk. Having them printed on paper helped me to understand the code of each decoder. Comparing several different decoder implementations helped me to understand the theory and algorithms of the MP3 spec.