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@ -18,18 +18,19 @@ namespace BTNRH_FFT { |
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ilog2(int n) |
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{ |
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int m; |
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for (m = 1; m < 32; m++) |
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if (n == (1 << m)) |
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return (m); |
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return (-1); |
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} |
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static __inline int |
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bitrev(int ii, int m) |
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{ |
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register int jj; |
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// Was: register int jj; RSL 9 Oct 2024
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int jj; |
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jj = ii & 1; |
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--m; |
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while (--m > 0) { |
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@ -39,26 +40,26 @@ namespace BTNRH_FFT { |
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} |
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return (jj); |
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} |
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static __inline void |
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rad2(int ii, float *x0, float *x1) |
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{ |
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int k; |
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float t; |
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for (k = 0; k < ii; k++) { |
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t = x0[k] + x1[k]; |
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x1[k] = x0[k] - x1[k]; |
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x0[k] = t; |
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} |
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} |
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static __inline void |
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reorder1(int m, float *x) |
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{ |
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int j, k, kl, n; |
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float t; |
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k = 4; |
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kl = 2; |
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n = 1 << m; |
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@ -75,13 +76,13 @@ namespace BTNRH_FFT { |
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} |
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} |
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} |
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static __inline void |
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reorder2(int m, float *x) |
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{ |
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int ji, ij, n; |
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float t; |
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n = 1 << m; |
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for (ij = 0; ij <= (n - 2); ij += 2) { |
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ji = bitrev(ij >> 1, m) << 1; |
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@ -95,11 +96,11 @@ namespace BTNRH_FFT { |
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} |
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} |
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} |
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/***********************************************************/ |
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// rcfft
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static void |
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rcrad4(int ii, int nn, |
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float *x0, float *x1, float *x2, float *x3, |
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@ -109,7 +110,7 @@ namespace BTNRH_FFT { |
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float c1, c2, c3, s1, s2, s3, pr, pi, r1, r5; |
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float t0, t1, t2, t3, t4, t5, t6, t7; |
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int i0, i4, j, j0, ji, jl, jr, jlast, k, k0, kl, m, n, ni; |
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n = nn / 4; |
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for (m = 1; (1 << m) < n; m++) |
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continue; |
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@ -186,19 +187,19 @@ namespace BTNRH_FFT { |
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} |
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} |
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} |
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//-----------------------------------------------------------
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static int |
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rcfft2(float *x, int m) |
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{ |
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int ii, nn, m2, it, n; |
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n = 1 << m;; |
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m2 = m / 2; |
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// radix 2
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if (m <= m2 * 2) { |
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nn = 1; |
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} else { |
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@ -206,9 +207,9 @@ namespace BTNRH_FFT { |
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ii = n / nn; |
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rad2(ii, x, x + ii); |
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} |
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// radix 4
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if (m2 != 0) { |
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for (it = 0; it < m2; it++) { |
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nn = nn * 4; |
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@ -217,9 +218,9 @@ namespace BTNRH_FFT { |
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x, x + ii, x + 2 * ii, x + 3 * ii); |
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} |
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} |
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// re-order
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reorder1(m, x); |
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reorder2(m, x); |
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for (it = 3; it < n; it += 2) |
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@ -227,14 +228,14 @@ namespace BTNRH_FFT { |
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x[n] = x[1]; |
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x[1] = 0.0; |
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x[n + 1] = 0.0; |
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return (0); |
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} |
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/***********************************************************/ |
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// rcfft
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static void |
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crrad4(int jj, int nn, |
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float *x0, float *x1, float *x2, float *x3, |
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@ -244,7 +245,7 @@ namespace BTNRH_FFT { |
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float c1, c2, c3, s1, s2, s3; |
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float t0, t1, t2, t3, t4, t5, t6, t7; |
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int ii, j, j0, ji, jr, jl, jlast, j4, k, k0, kl, m, n, ni; |
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tpiovn = 2 * M_PI / nn; |
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ji = 3; |
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jl = 2; |
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@ -317,27 +318,27 @@ namespace BTNRH_FFT { |
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} |
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} |
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} |
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//-----------------------------------------------------------
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static int |
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crfft2(float *x, int m) |
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{ |
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int n, i, it, nn, jj, m2; |
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n = 1 << m; |
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x[1] = x[n]; |
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m2 = m / 2; |
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// re-order
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for (i = 3; i < n; i += 2) |
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x[i] = -x[i]; |
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reorder2(m, x); |
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reorder1(m, x); |
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// radix 4
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if (m2 != 0) { |
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nn = 4 * n; |
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for (it = 0; it < m2; it++) { |
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@ -347,39 +348,39 @@ namespace BTNRH_FFT { |
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x, x + jj, x + 2 * jj, x + 3 * jj); |
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} |
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} |
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// radix 2
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if (m > m2 * 2) { |
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jj = n / 2; |
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rad2(jj, x, x + jj); |
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} |
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return (0); |
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} |
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/***********************************************************/ |
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// real-to-complex FFT
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//FUNC(void)
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void cha_fft_rc(float *x, int n) |
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{ |
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int m; |
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// assume n is a power of two
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// assume n is a power of two
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m = ilog2(n); |
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rcfft2(x, m); |
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} |
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// complex-to-real inverse FFT
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//FUNC(void)
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void cha_fft_cr(float *x, int n) |
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{ |
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int i, m; |
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// assume n is a power of two
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// assume n is a power of two
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m = ilog2(n); |
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crfft2(x, m); |
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// scale inverse by 1/n
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@ -390,4 +391,4 @@ namespace BTNRH_FFT { |
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}; |
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//endif
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//endif
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