A-Law Compressor

Implement A-law compressor for source coding

Library

Source Coding

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Description

The A-Law Compressor block implements an A-law compressor for the input signal. The formula for the A-law compressor is

$$y=\{\begin{array}{ll}\frac{A\left|x\right|}{1+\log A}\mathrm{sgn}(x)\hfill & \text{for }0\le \left|x\right|\le \frac{V}{A}\hfill \\ \frac{V\left(1+\log (A\left|x\right|/V)\right)}{1+\log A}\mathrm{sgn}(x)\hfill & \text{for }\frac{V}{A}<\left|x\right|\le V\hfill \end{array}$$

where A is the A-law parameter of the compressor, V is the peak signal magnitude for x, log is the natural logarithm, and sgn is the sign function.

The most commonly used A value is 87.6.

The input can have any shape or frame status. This block processes each vector element independently.

Parameters

A value

The A-law parameter of the compressor.

Peak signal magnitude

The peak value of the input signal. This is also the peak value of the output signal.

Supported Data Type

Port	Supported Data Types
In	double
Out	double

Pair Block

A-Law Expander

References

[1] Sklar, Bernard. Digital Communications: Fundamentals and Applications. Englewood Cliffs, N.J., Prentice-Hall, 1988.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a