MP3
MP3 is the name commonly given to the audio formats specified by MPEG-1 Layer III and MPEG-2 Layer III, standardized as ISO/IEC 11172-3:1993. It uses lossy compressed data. It is based in part on work by the Fraunhofer Institute, which still holds patents in the format. Other companies may also hold patents encumbering its implementation. One of the relevant patents is U.S. Patent 5,812,672, which expires in September 2015; many other related patents in various countries are already expired. The final expiration of all relevant patents may not occur until 2017, however, due to some "submarine patents" which were kept in the application process for years, extending their expiration dates.
A modified version of DCT compression (Discrete cosine transform) is used, a lossy compression method also used in JPEG images.
The MP3 format (and other related ones) is standardized in ISO/IEC 11172-3:1993, with some additions in ISO/IEC 13818-3:1995.
ID3 tags are often used to provide metadata in MP3 files, though they aren't part of the MP3 specification.
References
Software
- MP3DirectCut -- MP3 editor
- LAME MP3 encoder: open-source
- LAME compiled libraries - needed for various software to let it import/export/use MP3s
- mp3stego: Hide information in MP3 files
