MP3

MP3

• Patent-encumbered.
  • MPEG standards are owned by the International Standardisation Organisation (ISO) .
  • The technology to create them is donated by the companies that participate in the MPEG process. Any company is free to develop contributions that improve a standard, and MPEG has a formal process by which it evaluates them.
  • ISO-MPEG developed the AAC standard. Among the many contributing companies were Fraunhofer IIS, University of Hannover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others.
  • At least some of the companies who contributed technology to the MP3 standard would own some of the patents involved in MP3.
  • Many organizations have claimed ownership of patents related to MP3 decoding or encoding. These claims have led to a number of legal threats and actions from a variety of sources, resulting in uncertainty about which patents must be licensed in order to create MP3 products without committing patent infringement in countries that allow software patents.
  • The various MP3-related patents expire on dates ranging from 2007 to 2017 in the U.S.
• MPEG-1 or MPEG-2 Audio Layer III, is commonly referred to as MP3.
• It was designed by Moving Picture Experts Group (MPEG) Audio Subgroup (with participation of several teams of engineers from Fraunhofer IIS, University of Hannover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others) as part of its MPEG-1 standard and later extended in MPEG-2 standard.
• MPEG-1 Audio (MPEG-1 Part 3); which included MPEG-1 Audio Layer I, II and III was approved as a committee draft of ISO/IEC standard in 1991, finalised in 1992 and published in 1993 (ISO/IEC 11172-3:1993). Backwards compatible MPEG-2 Audio (MPEG-2 Part 3) with additional bit rates and sample rates was published in 1995 (ISO/IEC 13818-3:1995).
• Can contain up to 2 channels of sound.
• Limited to a fixed number of bitrates (unlike AAC); with an upper bound of 320 kbps.
  • Can be encoded at different bitrates: 64 kbps, 128 kbps, 192 kbps, and a variety of others from 32 to 320. Higher bitrates mean larger file sizes and better quality audio, although the ratio of audio quality to bitrate is not linear. (128 kbps sounds more than twice as good as 64 kbps, but 256 kbps doesn’t sound twice as good as 128 kbps.)
  • Allows for variable bitrate encoding, which means that some parts of the encoded stream are compressed more than others. For example, silence between notes can be encoded at a low bitrate, then the bitrate can spike up a moment later when multiple instruments start playing a complex chord. MP3s can also be encoded with a constant bitrate, which, unsurprisingly, is called constant bitrate encoding.
• Encoders
  • The MP3 standard doesn’t define exactly how to encode MP3s (although it does define exactly how to decode them); different encoders use different psychoacoustic models that produce wildly different results, but are all decodable by the same players.
  • The open source LAME project is the best free encoder, and arguably the best encoder period for all but the lowest bitrates.
• Players
  • Adobe Flash Player can play both standalone MP3 files and MP3 audio streams within an MP4 video container.
  • Pretty much every portable music player supports standalone MP3 files, and MP3 audio streams can be embedded in any video container.
• Operating Systems :-
  • MP3 format (standardized in 1991) is patent-encumbered, which explains why Linux can’t play MP3 files out of the box