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
Code:
test results
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test1.mp2 (125.8 MiB, 54min 57sec, 320kbps, 48kHz, stereo, source: DVB-S radio)
program options compressed size unpackmp2 gain
----------------- ----------------- ------------------ ---------------------
unpackmp2 | lpaq8 5 110859854 = 84.0% 12489717 (11.9 MiB)
unpackmp2 | 7-Zip 7z LZMA ultra 117928435 = 89.4% 8262710 (7.9 MiB)
unpackmp2 | 7-Zip 7z Bzip2 ultra 119080485 = 90.3% 7493074 (7.1 MiB)
unpackmp2 | 7-Zip 7z PPMd ultra 120598552 = 91.4% 4933122 (4.7 MiB)
unpackmp2 | 7-Zip Zip Deflate ultra 120718098 = 91.5% 6127333 (5.8 MiB)
lpaq8 5 123349571 = 93.5% (n/a)
7-Zip 7z PPMd ultra 125531674 = 95.2% (n/a)
7-Zip 7z LZMA ultra 126191145 = 95.7% (n/a)
7-Zip 7z Bzip2 ultra 126573559 = 96.0% (n/a)
7-Zip Zip Deflate ultra 126845431 = 96.2% (n/a)
(original mp2) (n/a) 131912640 = 100.0% (n/a)
unpackmp2 (n/a) 202374495 = 153.4% -70461855 (-67.2 MiB)