# ⓘ Audio codecs ..

## A-law algorithm

An A-law algorithm is a standard companding algorithm, used in European 8-bit PCM digital communications systems to optimize, i.e. modify, the dynamic range of an analog signal for digitizing. It is one of two versions of the G.711 standard from ITU-T, the other version being the similar μ-law, used in North America and Japan. For a given input X, the equation for a-law encoding is as follows, F x = sgn ⁡ x { A | x | 1 + ln ⁡ A, | x | &lt, 1 A 1 + ln ⁡ A | x | 1 + ln ⁡ A, 1 A ≤ | x | ≤ 1, {\displaystyle Fx=\operatorname {sgn}x{\begin{cases}{A|x| \over 1+\lnA},&amp,|x|

## AptX

The original aptX algorithm was developed in the 1980s by Dr. Stephen Smyth as part of his Ph.D. research at Queens University Belfast School of Electronics, Electrical Engineering and Computer Science, its design is based on time domain ADPCM principles without psychoacoustic auditory masking techniques. aptX audio coding was first introduced to the commercial market as a semiconductor product, programming of DSP integrated circuit with part name APTX100ED, which was initially adopted by broadcast automation equipment manufacturers who required to store CD-quality audio on computer hard d ...

## Asao (codec)

Asao is a proprietary single-channel codec and compression format optimized for low-bitrate transmission of audio, developed by Nellymoser Inc.

## Cook Codec

The cook codec is a lossy audio compression codec developed by RealNetworks. It is also known as Cooker, Gecko, RealAudio G2, and RealAudio 8 low bitrate. Introduced in 1998, the codec cook was the first Audio codec developed by RealNetworks in the house, and was named in honor of its author, Ken cook. The design is largely based on G. 722.1. This is a pure transform codec based on the modified discrete cosine transform with a single block size. In 2003, RealNetworks introduced a surround sound version of cook, called realaudio multichannel product. It was originally scheduled for the four ...

## Enhanced Audio Codec

Enhanced Audio Codec is an audio codec developed and owned by Beijing E-World, that uses a unique perceptual model, spectral band replication, to compress the audio signal by utilizing the redundancy as well as the relevancy. The EAC codec supports mono, stereo and 5.1 surround sound modes for encoding and decoding. EAC is part of the EVD system specification.

## Harmonic and Individual Lines and Noise

Harmonic and Individual Lines and Noise is a parametric codec for audio. The basic premise of the encoder is that most audio, and particularly speech, can be synthesized from only sinusoids and noise. The encoder describes individual sinusoids with amplitude and frequency, harmonic tones by fundamental frequency, amplitude and the spectral envelope of the partials, and the noise by amplitude and spectral envelope. This type of encoder is capable of encoding audio to between 6 and 16 kilobits per second for a typical audio bandwidth of 8 kHz. The framelength of this encoder is 32 ms. A typi ...