RM0020 datasheet(31/69 Pages) STMICROELECTRONICS

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RM0020

Function API

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Arguments:

Description:

Windowing function for real float data. Input data are stored in x vector, output data

are written into y vector. The y vector can be the same as x vector (in-place

windowing).

Algorithm:

Equation 27

for each k = 0,1,...N-1

Note: There must be 16 bytes of readable memory behind input vector x and 8 bytes of

readable memory behind window vector w.

Performance: See Section 7 and Table 44.

Example 13. window_apply_real_float

#include "libdsp2.h"

float x[64+4];

/* +4 to ensure there is 16 bytes of readable

memory behind buffer */

float w[64+2];

/* +2 to ensure there is

8 bytes of readable

memory behind buffer */

void main(void)

{

unsigned int i, N;

/* length of vectors is 64 */

N = 64;

/* prepare example input data */

for (i = 0; i < N; i++) x[i] = i+1;

for (i = 0; i < N; i++) w[i] = i+N;

/* windowing function on real float data, x[i] = x[i]*w[i] */

window_apply_real_float(N, x, x, w);

}

6.14

Real frac16 windowing function

Function call:

void window_apply_real_frac16(unsigned int N, short *x, short *y,

short *w);

Table 13.

window_apply_real_float arguments

length of vectors, must be multiple of 16

x(1)

All vectors must be double word aligned. All vectors have the following memory layout:

x(0) x(1)... x(N-1).

pointer to the input vector of length N

y(1)

out

pointer to the output vector of length N, y vector can be the same

as x vector (in-place windowing)

w(1)

pointer to the window vector of length N



wk



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