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<HTML>
<HEAD>
<TITLE>TSP (libtsp/FI) - FIfiltAP</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFACD">
<H2>FIfiltAP</H2>
<HR>
<H4>Routine</H4>
<DL>
<DT>
void FIfiltAP (const float x[], float y[], int Nout, const float h[],
int Ncof)
</DL>
<H4>Purpose</H4>
<DL>
<DT>
Filter a signal with an all-pole IIR filter
</DL>
<H4>Description</H4>
The procedure filters an input signal using an all-pole filter. The filter
is specified by its direct-form feeback coefficients h[i],
<PRE>
1 N-1 -i
H(z) = ---- , where C(z) = SUM h[i] z .
C(z) i=0
</PRE>
<P>
The output is calculated as
<PRE>
h[0]*y[k] = x[k] - h[1]*y[k-1] - h[2]*y[k-2] - ...
- h[Ncof-1]*y[k-Ncof+1].
</PRE>
Normally, the first coefficient is unity, i.e. h[0]=1. A non-unity value
will result in a gain scaling of the response.
<P>
The output array y[.] must be primed with mem=Ncof-1 previous output values.
On return the top mem values in y[.] can serve as the memory values for the
next invocation of this routine.
<P>
This routine can also be called with a single array x[.] of length mem+Nout,
<PRE>
FIfiltAP (&x[mem], x, Nout, h, Ncof)
</PRE>
Before entering this routine, the first mem values of x[.] are set to
previous output values, while the next Nout values are new input values.
On return, the Nout new output values replace the input values, starting at
x[mem]. If the top mem elements are shifted down to the bottom of the array,
these can serve as the previous output values for the next call to this
routine.
<H4>Parameters</H4>
<DL>
<DT>
-> const float x[]
<DD>
Input array of data, Nout values
<DT>
<-> float y[]
<DD>
Output array of samples. This array is of length Ncof-1+Nout. On input,
the first Ncof-1 values should represent past output values. On output,
Nout new output samples are appended to this array.
<DT>
-> int Nout
<DD>
Number of new output samples to be calculated
<DT>
-> const float h[]
<DD>
Array of Ncof all-pole filter coefficients. The first coefficient must
be non-zero.
<DT>
-> int Ncof
<DD>
Number of filter coefficients
</DL>
<H4>Author / revision</H4>
P. Kabal Copyright (C) 1997
/ Revision 1.11 1997/10/10
<P>
<HR>
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