MP3: MPEG 1 Layer 3
The MP3 algorithm development started in 1987, with a joint cooperation of Fraunhofer IIS-A and the University of Erlangen. It is standardized as ISO-MPEG Audio Layer-3 (IS 11172-3 and IS 13818-3).
It soon became the de facto standard for lossy audio encoding, due to the high compression rates (1/11 of the original size, still retaining considerable quality), the high availability of decoders and the low CPU requirements for playback. (486 DX2-100 is enough for real-time decoding)
Formal and informal listening tests have shown that MP3 at the 160-224 kbps range provide encoded results undistinguishable from the original materials in most of the cases.
- Widespread acceptance, support in nearly all hardware audio players and devices
- An ISO standard, part of MPEG specs
- Fast decoding, lower complexity than AAC or Vorbis
- Anyone can create their own implementation (Specs and demo sources available)
- Relaxed licensing schedule
- Lower performance / efficiency than modern codecs.
- Problem cases that trip out all transform codecs.
- Sometimes, maximum bitrate (320kbps) isn't enough.
- No multichannel implementations.
- Unusable for high definition audio (sampling rates higher than 48kHz).
Techniques used in compression
- Huffman coding
- M/S matrixing
- Intensity stereo
- Channel coupling
- Modified discrete cosine transform (MDCT)
- Polyphase filter bank
There is a non-standardized form of MP3 called MP3pro, which takes advantage of SBR encoding to provide better quality at low bitrates.
Encoders / Decoders (Supported Platforms)
- LAME (Win32/Posix)