unpackmp2 is a filter program that performs a lossless transformation of MPEG audio Layer II data (mp2) into an unpacked format and back into mp2 format.
It is intended to be used as a preprocessor for lossless compression programs in order to achieve a better compression of mp2 files.

The attached archive contains Windows executables and scripts.
Also included is the full source code. It should compile under Linux and other systems as well.
This is free software under GNU GPL v3, http://www.gnu.org/copyleft/gpl.html

v1.0.1 (2009-11-10)
-added MPEG frame protection (CRC) support
-compiled with switch "-static-libgcc" to remove dependency on libgcc_s_dw2-1.dll

Thanks. I've tried it and compresses better than I had expected.
But why not unpackMP3? I think it would be much more useful for people.

For mp3 there is already mp3packer, hardly there will be something better soon.

Well, such a program would be much more complex than unpackmp2, because of the advanced features of the MP3 format (Huffman coding, bit reservoir). And I am not THAT interested in mp3 - I just want to archive several gigabytes of MP2 files... (see is lossless MP2 to MPC conversion possible?)

But there is a significant difference:
mp3packer is used to create slightly smaller, but still standard mp3 files that every mp3 player in the world can play.
unpackmp2 on the other hand creates unpacked files in its own format that are bigger than the original mp2 (about 150-170%) but more compressible by some external file archivers. Only unpackmp2 can convert those files back into standard mp2 format.

A hypothetical "unpackmp3" program could be feasible. It would complement mp3packer for file archiving purposes.

It is interesting that modified MPC encoder can produce MP2 files: http://www.hydrogenaudio.org/forums/index....ost&p=11064. But AFAIK that codec was never released.

а.п.т. with 'unpackMP3' you can achieve much more as you can ditch weak huffman encoding and use something better. There is such program already called SoundSlimmer and it is amazing (nothing comes close). I created a topic about it back then http://www.hydrogenaudio.org/forums/index....showtopic=44102. It is payware, so something free with compression comparable to SoundSlimmer IMHO would be a revolution.

Straying a bit from the topic, but I wonder how much smaller you could make MP3 files with a context-based arithmetic coder (like H.264 has). Of course this is generally what you would be doing with a hypothetical "unpackMP3" and a modern compressor.