Programmer Guide/SPU Reference/LIMITER

LIMITER - amplitude limiter (non-linear)

The LIMITER spatom applies a non-linear magnitude weighting to the signal. The limiter function is only applied if the absolute value of the signal magnitude is higher than the specified limiter start magnitude LIM. For the limiter function, the following algorithm is used:

with:

x, y	input and output signal sample
LIM, MAX	limiter start amplitude and maximum signal amplitude
f()	limiter function selected by input TYPE

Table: Limiter functions{| |- |The value of TYPE |The limiter function f(z) |- |0 or RECTANGLE |File:1241.png ('cut-off') |- |1 or ATAN |File:1242.png |- |2 or EXPONENTIAL |File:1243.png |}

with:

The output Q is set to the relative number of processed samples:

Q = number of changed samples / number of processed samples

Usage:

LIMITER X TYPE MAX LIM

Inputs:

X

The signal vector or sample.

TYPE

The type of limiter function (see table above).

MAX

The maximum magnitude (full attenuation).

LIM

The limiter start magnitude. This value must be less than MAX.

Outputs:

Y

The limited signal (the same type as X).

Q

The relative number of limited (changed) samples.