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µ law method

The µ-law method is a method used to increase the dynamic range of an audio signal before digital transmission. This method is described in the ITU recommendationG.711 and is used in PCM systems.

In µ-law compression, the dynamic range is increased by first sampling the signal at a higher bit rate and then compressing the data to a lower bit rate using a specific algorithm. The receiver of such a signal works in exactly the opposite way and restores the original higher bit rate.

Like the A-law method, the µ-law method also works with nonlinear characteristics and uses different quantization levels than the A-law method. Determining the bit rate is somewhat problematic in the µ-Law method, since the quantization samples are encoded logarithmically with 8 bits, whereas their dynamic range is encoded linearly with 13 bits. In the low level range, µ-Law has a steeper dynamic characteristic curve than the A-Law method.

Functional units of µ-law compression

Functional units of µ-law compression

The µ-law method is used in ISDN in the USA and Japan, since the ISDN technology there requires alternating bit states to generate the clock signal and cannot process continuous 0 sequences.

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Englisch: µ law method
Updated at: 23.04.2013
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