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.
Support for a-law 8kHz audio format is also now available in this new version.
The files are recorded in mu-law format for tProbe[TM] T1 and in A-law for tProbe[TM] E1.
Designed specifically for use in IAD gateways at the edge of a packet network to cancel 4-wire-to-2-wire echo, the flexible GIPS NEC - IAD package offers adaptive comfort noise insertion and supports linear, A-law and u-law inputs, and is not affected by double-talk.
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.
R1, R2, and DTMF, as well as custom variants for over 80 countries, and perform mu-Law to A-Law rate conversion.
R1, R2, and DTMF, as well as custom variants for over 80 countries, and (mu)-Law to A-Law rate conversion.
It combines the Audio Processing (DTMF Detection and Generation, A-law and Mu-law Codecs), Real-Time multi-media modules (SIP, SDP, RTP/RTCP) and Network Protocol Stack (UDP, IP, DHCP, ICMP), with a highly efficient Operating System specially designed for media streaming over IP Networks.