Rfft2D - Analog Devices VISUALDSP++ 3.5 Manual

DSP Run-Time Library Reference

rfft2d

NxN point 2-D real input FFT
Synopsis
#include <filter.h>
void rfft2d_fr16(*in, *t, *out, w[], wst, n, block_exponent,
const fract16 *in;
complex_fract16 *t;
complex_fract16 *out;
const complex_fract16 w[]; /* twiddle sequence
int wst;
int n;
int *block_exponent;
int scale method;
Description
This function computes a two-dimensional Fast Fourier Transform of the
real input matrix
matrix
c[n][n]
The size of the input array
working buffer
FFT. The function does not impose any special memory alignment
requirements on the arrays. However, benefits in run-time performance
will be realized if the output array is allocated on an address boundary that
is a multiple of twice the FFT size.
The twiddle table is passed in the argument
twiddle coefficients. The function
n/2
tialize the array. If the twiddle table contains more coefficients than
needed for a particular call on
be set appropriately; otherwise it should be one.
4-98
scale_method)
/* pointer to input matrix a[n][n]
/* pointer to working buffer t[n][n] */
/* pointer to output matrix c[n][n] */
/* twiddle factor stride
/* number of FFT points
/* block exponent of output data
/* scaling method desired 0-none,
, and stores the result to the complex output
a[n][n]
.
, the output array
in
is , where represents the number of points in the
t n*n n
rfft2d_fr16
VisualDSP++ 3.5 C/C++ Compiler and Library Manual
1-static, 2-dynamic
, and the temporary
out
, which must contain at least
w
twidfft2d_fr16
, then the stride factor has to
for ADSP-219x DSPs
*/
*/
*/
*/
*/
*/
may be used to ini-