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MP3 (formerly MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) [4] is a digital audio coding format widely developed by Fraunhofer-Gesellschaft in Germany with support for a. A large number of other digital scientists have been developed in the Unitedx States, and therefore elsewhere. Originally defined as the third hard disk of an MPEG-1 audio computer, it has been retained and expanded – defines free bitrates and supports more audio channels – as a third audio format after the standard MPEG-2 type. A third well-known style, such as MPEG 2.5, extended to better support lower bit rates, is usually implemented, but not a fixed standard.
MP3 (or mp3) as a file format generally refers to files containing an elementary stream added to the audio data of an MPEG-1 or MPEG-2 encoded audio recording without any other complexity of the MP3 standard.
Regarding audio compression (the most obvious aspect of the standard to end users and therefore the most well-known), MP3 uses lossy data compression to encode data that works with imprecise approximations and partial cancellation, including data. This allows the file size to be significantly reduced compared to the uncompressed MP3 format. A combination of small size and adequate fidelityThis led to a boom in online music distribution in the mid to late 1990s, when small MP3 bowls served as the backbone of the technology during a precious time when band traffic and storage were still a bonus to visit. The MP3 format will soon be linked to disputes over copyright infringement, your favorite music and piracy, as well as the copying and sharing services MP3.com and Napster. With the advent of portable media players, a product that also includes smartphones, mp3 support continues almost everywhere.
MP3 compression works by reducing (or approximating) the accuracy of certain sound components that are considered (by psychoacoustic analysis) the most audible abilities of most people. This technique is commonly referred to as perceptual or psychoacoustic simulation coding. [9] The remaining audio information is then saved to save space using the MDCT and fft algorithms. Compared to CD-quality digital audio, MP3 compression can typically go up to 75 for a 95% reduction in size. For example, an efficient MP3 file encodedPowered at a constant bit rate of 128 kbps, it will make a file about 9% larger than the size of a revolutionary audio CD. [10] Disk was compressed very early in the 2000s. Players are increasingly supporting the playback of MP3 files on data CDs.
The Moving Picture Experts Group (MPEG) developed the MP3 format as part of the MPEG-1 and later MPEG-2 standards. MPEG-1 Audio (MPEG-1 Part 3), which specifically included MPEG-1 Audio Layer I, II in combination with III, was approved as a committee version for the ISO / IEC standard in 1991, [11] < / sup> [12] Completed 1992, [13] and published 1993, hence ISO / IEC 11172-3: 1993. [6] The MPEG-2 Audio Part (mpeg-2 3) extension with lower sampling and bit rates was released in 1995 as ISO / IEC 13818-3: 1995. [7] [14]] This requires minimal modifications to the latest MPEG-1 decoders (recognizes MPEG-2 in the header and adds new samples and bitrates frequently).
History
Context
The lossy MP3 audio data compression algorithm uses a perceptual limitation of the human ear called masking. VIn 1894, the American physicist Alfred M. Mayer reported that a building might not be heard in a different environment with a lower frequency. [15] In 1959, Richard Amer described the full range of auditory distortions associated with this phenomenon. [16] Between 1967 and 1973, Eberhard Zwicker worked in cameras, tuning and masking frequency bands, [17] [18] correctly noted, which once again drew on critical research in this area by Harvey Fletcher and colleagues at Bell Labs. [19]
Perceptual computer programming was first used to encode speech using Linear Predictive Coding (LPC), [20] , which has its origins in the work of Fumitada Itakura (Nagoya University) and Shuzo Saito (Nippon Telegraph and Telephone) in 1966. [21] In 1978, Bishnu S. Atal and Manfred R. Schroeder, through Bell Labs, proposed an LPC speech model codec called adaptive predictive coding and best psychoacoustic coding. an encoding algorithm used that uses masking properties of the human ear. [20] [22] Another optimizationA study by Schroeder and Atal with JL Hall was published later in a 1979 article. [23] In the same year, M.A. Krasner may have proposed a psychoacoustic masking codec, [24] , which introduced and prepared material for speech (as opposed to music bit compression), but publishing his results in a relatively little-known Lincoln Laboratory technical report [25] did not happen immediately. This is the result of the general development of psychoacoustic codecs.
Individually Differing Cosine Transform (DCT), an HTML transform type HTML encoding proposed by Nasir Ahmed in 1972, was developed by Ahmed T. Natarajan and KR Rao using They 1973; published their results around 1974. [26] [27] [28] This led to the development of the commonly modified Discrete Cosine Transform (MDCT). proposed by JP Princen, the trial of AW Johnson, not forgetting AB Bradley in 1987, [29] based on previous work by Princen and Bradley in 1986. [30] MDCT later became the core of the step in the MP3 algorithm. [31]
Ernst Terhardt W. built a descriptive algorithm in 1982m for acoustic masking with high accuracy of the critical bandwidth.
1985 Atal and Schroeder publish Code Linear Prediction (CELP), an LPC-based perceptual voice coding algorithm with auditory masking that imposes significant data compression in relation to its time. [20] IEEE The Journal on Selected Area in Communications reported a wide variety of audio compression algorithms (mostly perceptual) in 1988. [33] Adapted from February 1988 Voice Coding for Communications reported a wide range of functional Small-bit audio compression technologies, [33] some of them use oral masking as part of their core type, and some show real-time hardware implementations.
Development
The emergence of MP3 technology is detailed in an article by Professor Hans Musmann, [34] , who headed the ISO MPEG audio division for several years. In December 1988, MPEG demanded an audio coding standard. Finally, in 1989, on June 14, the audio coding algorithms were introduced. Due to some similarities between the departmentWith new coding suggestions, they were grouped into 6 development groups. The first ASPEC group included Fraunhofer Gesellschaft, AT&T, France Telecom, Deutsche and Thomson-Brandt. The second group consisted of MUSICAM, Matsushita from CCETT, ITT and Philips. The third group, ATAC, was formed by Fujitsu, JVC, NEC and Sony. And fourth, the SB-ADPCM association from NTT and BTRL. [34]
The automatic predecessors of MP3 were Optimal Coding Using Frequency Domain (OCF), [35] , and Perceptual Transform (PXFM). [36] These two codecs, along with Thomson-Brandt’s contribution to block switching, were immediately merged into a codec called ASPEC, which was outsourced to MPEG.
