68 lines
1.3 KiB
C
68 lines
1.3 KiB
C
/*
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* Contributor(s):
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*
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* Eric des Courtis <eric.des.courtis@benbria.com>
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* Piotr Gregor <piotrgregor@rsyncme.org>
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*/
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#include <stdio.h>
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#ifdef WIN32
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#include <float.h>
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#define ISNAN(x) (!!(_isnan(x)))
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#define ISINF(x) (isinf(x))
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#endif
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#include "avmd_buffer.h"
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#include "avmd_desa2.h"
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#include "avmd_options.h"
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#ifdef AVMD_FAST_MATH
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#include "avmd_fast_acosf.h"
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#endif
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double avmd_desa2(circ_buffer_t *b, size_t i, double *amplitude) {
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double d;
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double n;
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double x0;
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double x1;
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double x2;
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double x3;
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double x4;
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double x2sq;
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double result;
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double PSI_Xn, PSI_Yn, NEEDED;
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x0 = GET_SAMPLE((b), (i));
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x1 = GET_SAMPLE((b), ((i) + 1));
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x2 = GET_SAMPLE((b), ((i) + 2));
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x3 = GET_SAMPLE((b), ((i) + 3));
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x4 = GET_SAMPLE((b), ((i) + 4));
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x2sq = x2 * x2;
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d = 2.0 * ((x2sq) - (x1 * x3));
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if (d == 0.0) {
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*amplitude = 0.0;
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return 0.0;
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}
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PSI_Xn = ((x2sq) - (x0 * x4));
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NEEDED = ((x1 * x1) - (x0 * x2)) + ((x3 * x3) - (x2 * x4));
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n = ((x2sq) - (x0 * x4)) - NEEDED;
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PSI_Yn = NEEDED + PSI_Xn;
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#ifdef AVMD_FAST_MATH
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result = 0.5 * (double)fast_acosf((float)n/d);
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#else
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result = 0.5 * acos(n/d);
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#endif
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if (ISNAN(result)) {
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result = 0.0;
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}
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*amplitude = 2.0 * PSI_Xn / sqrt(PSI_Yn);
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return result;
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}
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