A MPEG Audio Layer II decoder in 4k

Last week, I read a paper on how to partially encrypt MPEG Audio data. That is, modify an existing audio file that it is still syntactically correct, but sounds more or less broken. For example, imagine an online music shop that offers free, but partially encrypted music downloads: The files are in bad quality, and you have to pay to restore the full fidelity. But I digress.
The point is: that paper was inspiring. I decided to try the presented method using MPEG-1 Audio Layer II (»MP2«) as a basis. I chose this format because it’s the simplest audio compression scheme that is still in broad use today (for example VCD/SVCD, DAB and most prominently DVB). Layer III (»MP3«), AAC and Vorbis are considerably more complex. And, it just so happened that I got a copy of ISO 11172-3 (MPEG-1 Audio) on my hard disk :)
While working on the project, I thought that it’d be cooler to write a full decoder instead of this mere proof-of-concept »look what I can do to my MP2 files« hack. So I developed a small MPEG-1 Audio Layer II decoding library called kjmp2 which eventually evolved into a less-than-4k MP2 player application …
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