Encoding an mp3
What is masking
The lossy MP3 audio compression algorithm uses a limitation of human hearing perception called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be made inaudible by another tone of a lower frequency. In 1959, Richard Amer described a complete set of auditory curves related to this phenomenon. Between 1967 and 1974, Eberhard Zwicker worked on tuning and masking critical frequency bands, which in turn built on the fundamental research of Harvey Fletcher and his collaborators at Bell Labs in this area. Perceptual coding was first used to compress speech coding with Linear Prediction Coding (LPC), which has its origins in the works Fuminada Itakura (Nagoya University) and Shuji Saito (from Nippon Telegraph and Telephone) in 1966. In 1978, Bishnu S. Atal and Manfred R. Schroeder of Bell Labs proposed an LPC speech codec called adaptive predictive coding. , which used a psychoacoustic coding algorithm using the masking properties of the human ear. Schroeder and Atal’s further optimization with J.L. Hall was later described in a 1979 article. In the same year M.A. Krasner proposed a psychoacoustic masking codec, which published and produced hardware for speech (not used to compress musical bits), but the publication of its results in a relatively obscure technical report from the Lincoln Laboratory did not immediately influence the mainstream of the development of psychoacoustic codecs. The Discrete Cosine Transform (DCT), a type of transform coding for lossy compression, proposed by Nasir Ahmed in 1972, was developed by Ahmed with T. Natarajan and KR Rao in 1973; published their results in 1974. This led to the development of the Modified Discrete Cosine Transform (MDCT) proposed by JP Princen, AW Johnson, and AB Bradley in 1987 after earlier work by Princen and Bradley in 1986. MDCT later became the main body of the MP3 algorithm. Ernst Terhardt et al. Built an algorithm that describes auditory masking with high precision in 1982. This work adds to many reports by authors dating back to Fletcher, as well as work that originally defined critical ratios and critical bandwidth. In 1985, Atal and Schroeder introduced Code Excited Linear Prediction (CELP), an LPC-based perceptual speech coding auditory masking algorithm that achieved a significant degree of data compression for its time. IEEE peer-reviewed journal “Favorite Communications” reported on a wide variety of audio compression algorithms (mainly perceptual) in 1988. The February 1988 issue of Voice Coding for Communication reported on a wide range of audio compression algorithms bit-based established and operational. technologies, some of which use auditory masking as part of their core design, and some of which show real-time hardware implementations. – https://ru.qaz.wiki/wiki/MP3
