A-law


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Related to A-law: Law society, u-Law

A-law

(standard)
The ITU-T standard for nonuniform quantising logarithmic compression.

The equation for A-law is

| A | ------- (m/mp) |m/mp| =< 1/A | 1+ln A y = | | sgn(m) | ------ (1 + ln A|m/mp|) 1/A =< |m/mp| =< 1 | 1+ln A

Values of u=100 and 255, A=87.6, mp is the Peak message value, m is the current quantised message value. (The formulae get simpler if you substitute x for m/mp and sgn(x) for sgn(m); then -1 <= x <= 1.)

Converting from u-LAW to A-LAW introduces quantising errors. u-law is used in North America and Japan, and A-law is used in Europe and the rest of the world and international routes.

[The Audio File Formats FAQ]

A-Law

An ITU standard for converting analog data into digital form using pulse code modulation (PCM). A-Law uses a companding technique that provides more quantizing steps at lower amplitude (volume) than at higher amplitude. Europe uses A-Law, while North America and Japan use mu-Law (µ-Law). See PCM and mu-Law.
References in periodicals archive ?
This paper is organized as follows: A general analysis of non-uniform scalar quantization and A-law companding is given in Section 2.
722 over TDM: In both A-Law and [micro]-Law PCM (64kbps), 8 bits are required to represent each sample.
Different encoding formats like [micro]-law, A-law, 16 bit, and 13 bit PCM captures are supported (requires VBA038 License) and also it can process V.
The files are recorded in mu-law format for tProbe[TM] T1 and in A-law for tProbe[TM] E1.
Kulkarni further added, “The enhancements introduced to Oscilloscope and Power Spectral Display applications include options for displaying all signaling formats - A-Law, Mu-Law, PCM 16 bit, PCM 13 bit, PCM 14 bit, PCM 8 bit and different byte order for INTEL (Little Endian) and MOTOROLA (Big Endian) 16 bit signals sampled at 16 KHz can also be displayed.