MAD is a high-quality MPEG audio decoder. It currently supports MPEG-1 and the
MPEG-2 extension to lower sampling frequencies, as well as the de facto MPEG 2.5
format. All three audio layers -- Layer I, Layer II, and Layer III (i.e. MP3) --
are fully implemented.

MAD does not yet support MPEG-2 multichannel audio (although it should be
backward compatible with such streams) nor does it currently support AAC.

MAD has the following special features:
- 24-bit PCM output
- 100% fixed-point (integer) computation
- completely new implementation based on the ISO/IEC standards
- available under the terms of the GNU General Public License (GPL)

The software is distributed as a library (libmad) and command-line front-end
(madplay). Also included is an ID3 tag manipulation library (libid3tag).

WWW: https://www.underbit.com/products/mad/