Audio coding format

comparison between lossless FLAC (top) and lossy Opus (bottom) files for the same audio clip. The 20-24 kHz range is absent in the lossy audio file. A lossless audio coding format reduces the total data needed to represent a sound but can be de-coded to its original, uncompressed form. A lossy audio coding format additionally reduces the bit resolution of the sound on top of compression, which results in far less data at the cost of irretrievably lost information. Transmitted (streamed) audio is most often compressed using lossy audio codecs as the smaller size is far more convenient for distribution. The most widely used audio coding formats are MP3 and Advanced Audio Coding (AAC), both of which are lossy formats based on modified discrete cosine transform (MDCT) and perceptual coding algorithms. Lossless audio coding formats such as FLAC and Apple Lossless are sometimes available, though at the cost of larger files. Uncompressed audio formats, such as pulse-code modulation (PCM, or .wav), are also sometimes used. PCM was the standard format for Compact Disc Digital Audio (CDDA). ==History==

for PC, 1990 In 1950, Bell Labs filed the patent on differential pulse-code modulation (DPCM). Adaptive DPCM (ADPCM) was introduced by P. Cummiskey, Nikil S. Jayant and James L. Flanagan at Bell Labs in 1973. Perceptual coding was first used for speech coding compression, with linear predictive coding (LPC). Initial concepts for LPC date back to the work of Fumitada Itakura (Nagoya University) and Shuzo Saito (Nippon Telegraph and Telephone) in 1966. During the 1970s, Bishnu S. Atal and Manfred R. Schroeder at Bell Labs developed a form of LPC called adaptive predictive coding (APC), a perceptual coding algorithm that exploited the masking properties of the human ear, followed in the early 1980s with the code-excited linear prediction (CELP) algorithm which achieved a significant compression ratio for its time. provided the basis for the modified discrete cosine transform (MDCT) used by modern audio compression formats such as MP3 and AAC. MDCT was proposed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987, following earlier work by Princen and Bradley in 1986. The MDCT is used by modern audio compression formats such as Dolby Digital, MP3, ==List of lossy formats==

General Speech • Linear predictive coding (LPC) • Adaptive predictive coding (APC) • Code-excited linear prediction (CELP) • Algebraic code-excited linear prediction (ACELP) • Relaxed code-excited linear prediction (RCELP) • Low-delay CELP (LD-CELP) • Adaptive Multi-Rate (used in GSM and 3GPP) • Codec 2 (noted for its lack of patent restrictions) • Speex (noted for its lack of patent restrictions) • Modified discrete cosine transform (MDCT) • AAC-LD • Constrained Energy Lapped Transform (CELT) • Opus (mostly for real-time applications) == List of lossless formats ==

• Apple Lossless (ALAC – Apple Lossless Audio Codec) • Adaptive Transform Acoustic Coding (ATRAC) • Audio Lossless Coding (also known as MPEG-4 ALS) • Direct Stream Transfer (DST) • Dolby TrueHD • DTS-HD Master Audio • Free Lossless Audio Codec (FLAC) • Lossless discrete cosine transform (LDCT) • Meridian Lossless Packing (MLP) • Monkey's Audio (Monkey's Audio APE) • MPEG-4 SLS (also known as HD-AAC) • OptimFROG • Original Sound Quality (OSQ) • RealPlayer (RealAudio Lossless) • Shorten (SHN) • TTA (True Audio Lossless) • WavPack (WavPack lossless) • WMA Lossless (Windows Media Lossless) ==See also==