MPEG-1 Audio Layer II
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM), is a lossy audio compression format defined by ISO / IEC 11172-3 in conjunction with MPEG-1 Audio Layer I and MPEG Audio Layer -1 III (MP3). While MP3 is much more popular for PC and Internet applications, MP2 is still the dominant standard for streaming audio.
Development history from MP2 to MP3
The MPEG-1 Audio Layer 2 encoding was derived from MUSICAM (masking pattern adapted by Universal Subgroup Integrated Coding And Multiplexing), an audio codec developed by the Center commun d’études de télévision et télécommunications (CCETT), Philips and Institut für Rundfunktechnik (IRTfunktechnik) in 1989 as part of the EURECA 147 pan-European intergovernmental research initiative for the development of an audio and data transmission system to fixed, portable or mobile receivers (established in 1987).
MPEG audio
In the late 1980s, ISO’s Moving Picture Experts Group (MPEG) began an effort to standardize digital video and audio encoding, which is expected to have a wide range of applications in digital radio and television broadcasting ( later TOUCH, DMB, DVB) and use on CD-ROM (later Video CD). The MUSICAM audio encoding was one of 14 proposals for the MPEG-1 audio standard that were shipped to ISO in 1989.
The MPEG-1 audio standard was based on the existing MUSICAM and ASPEC audio formats.
The MPEG-1 audio standard included three audio “layers” (encoding techniques) now known as Layer I (MP1), Layer II (MP2), and Layer III (MP3).
All algorithms for MPEG-1 Audio Layer I, II, and III were approved as draft in 1991 by the ISO 11172 committee and completed in 1992 as part of MPEG-1, the first set of MPEG standards that led to the international ISO standard. / IEC 11172-3 (also known as Audio MPEG-1 or Part 3, MPEG-1) published in 1993. Additional work on MPEG audio was completed in 1994 as part of the second set of MPEG standards, MPEG-2, more formally known as International Standard ISO / IEC 13818-3 (also known as MPEG-2 Part 3 or MPEG-2 Audio backward compatible or MPEG-2 BC Audio), originally published in 1995. MPEG-2 Part 3 (ISO / IEC 13818 -3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sample rates are exactly half of those originally specified for MPEG-1 Audio. MPEG-2 Part 3 also expanded MPEG-1 audio, allowing audio programs with more than two channels to be encoded in 5.1 multichannel.
Component Layer III (MP3) uses a lossy compression algorithm that has been designed to dramatically reduce the amount of data required to present an audio recording and be like a decent reproduction of the original uncompressed audio for most listeners.
