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c9d027ea91
Unnecessary computation of arc cosine is omitted and convergence is checked on partial results. Original frequency is easily retrieved when needed.
55 lines
1.0 KiB
C
55 lines
1.0 KiB
C
#ifndef __AVMD_DESA2_H__
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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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#else
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#define ISNAN(x) (isnan(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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extern double avmd_desa2(circ_buffer_t *b, size_t i)
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{
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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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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) return 0.0;
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n = ((x2sq) - (x0 * x4)) - ((x1 * x1) - (x0 * x2)) - ((x3 * x3) - (x2 * x4));
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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)) result = 0.0;
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return result;
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}
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#endif /* __AVMD_DESA2_H__ */
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