Mercurial > hg > octave-nkf
annotate scripts/signal/fftfilt.m @ 14138:72c96de7a403 stable
maint: update copyright notices for 2012
author | John W. Eaton <jwe@octave.org> |
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date | Mon, 02 Jan 2012 14:25:41 -0500 |
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1 ## Copyright (C) 1994-2012 John W. Eaton |
2313 | 2 ## |
3 ## This file is part of Octave. | |
4 ## | |
5 ## Octave is free software; you can redistribute it and/or modify it | |
6 ## under the terms of the GNU General Public License as published by | |
7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
8 ## your option) any later version. | |
2313 | 9 ## |
10 ## Octave is distributed in the hope that it will be useful, but | |
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 ## General Public License for more details. | |
14 ## | |
15 ## You should have received a copy of the GNU General Public License | |
7016 | 16 ## along with Octave; see the file COPYING. If not, see |
17 ## <http://www.gnu.org/licenses/>. | |
1026 | 18 |
3367 | 19 ## -*- texinfo -*- |
20 ## @deftypefn {Function File} {} fftfilt (@var{b}, @var{x}, @var{n}) | |
3426 | 21 ## |
3367 | 22 ## With two arguments, @code{fftfilt} filters @var{x} with the FIR filter |
23 ## @var{b} using the FFT. | |
3426 | 24 ## |
3367 | 25 ## Given the optional third argument, @var{n}, @code{fftfilt} uses the |
26 ## overlap-add method to filter @var{x} with @var{b} using an N-point FFT. | |
3890 | 27 ## |
28 ## If @var{x} is a matrix, filter each column of the matrix. | |
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29 ## @seealso{filter, filter2} |
3367 | 30 ## @end deftypefn |
2312 | 31 |
5428 | 32 ## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> |
2312 | 33 ## Created: 3 September 1994 |
34 ## Adapted-By: jwe | |
787 | 35 |
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36 function y = fftfilt (b, x, n) |
787 | 37 |
2325 | 38 ## If N is not specified explicitly, we do not use the overlap-add |
2303 | 39 ## method at all because loops are really slow. Otherwise, we only |
40 ## ensure that the number of points in the FFT is the smallest power | |
41 ## of two larger than N and length(b). This could result in length | |
42 ## one blocks, but if the user knows better ... | |
2325 | 43 |
787 | 44 if (nargin < 2 || nargin > 3) |
6046 | 45 print_usage (); |
787 | 46 endif |
2325 | 47 |
3890 | 48 transpose = (rows (x) == 1); |
49 | |
50 if (transpose) | |
51 x = x.'; | |
52 endif | |
53 | |
787 | 54 [r_x, c_x] = size (x); |
55 [r_b, c_b] = size (b); | |
56 | |
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57 if (! isvector (b)) |
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58 error ("fftfilt: B must be a vector"); |
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59 endif |
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60 |
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61 if (ndims (x) != 2) |
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62 error ("fftfilt: X must be a 1-D or 2-D array"); |
787 | 63 endif |
2325 | 64 |
3890 | 65 l_b = r_b * c_b; |
66 b = reshape (b, l_b, 1); | |
2325 | 67 |
787 | 68 if (nargin == 2) |
2303 | 69 ## Use FFT with the smallest power of 2 which is >= length (x) + |
70 ## length (b) - 1 as number of points ... | |
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71 n = 2 ^ nextpow2 (r_x + l_b - 1); |
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72 B = fft (b, n); |
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73 y = ifft (fft (x, n) .* B(:, ones (1, c_x))); |
787 | 74 else |
2303 | 75 ## Use overlap-add method ... |
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76 if (! (isscalar (n))) |
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77 error ("fftfilt: N has to be a scalar"); |
787 | 78 endif |
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79 n = 2 ^ nextpow2 (max ([n, l_b])); |
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80 L = n - l_b + 1; |
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81 B = fft (b, n); |
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82 B = B(:, ones (c_x,1)); |
3890 | 83 R = ceil (r_x / L); |
84 y = zeros (r_x, c_x); | |
1026 | 85 for r = 1:R; |
3890 | 86 lo = (r - 1) * L + 1; |
87 hi = min (r * L, r_x); | |
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88 tmp = zeros (n, c_x); |
3890 | 89 tmp(1:(hi-lo+1),:) = x(lo:hi,:); |
90 tmp = ifft (fft (tmp) .* B); | |
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91 hi = min (lo+n-1, r_x); |
3890 | 92 y(lo:hi,:) = y(lo:hi,:) + tmp(1:(hi-lo+1),:); |
2325 | 93 endfor |
787 | 94 endif |
2325 | 95 |
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96 y = y(1:r_x, :); |
3890 | 97 if (transpose) |
98 y = y.'; | |
99 endif | |
787 | 100 |
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101 ## Final cleanups: If both x and b are real, y should be real. |
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102 ## If both x and b are integer, y should be integer. |
1026 | 103 |
3890 | 104 if (isreal (b) && isreal (x)) |
787 | 105 y = real (y); |
106 endif | |
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107 if (! any (b - fix (b))) |
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108 idx = !any (x - fix (x)); |
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109 y(:, idx) = round (y(:, idx)); |
787 | 110 endif |
111 | |
112 endfunction | |
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113 |
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114 |
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115 %!shared b, x, r |
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116 %!test |
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117 %! b = [1 1]; |
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118 %! x = [1, zeros(1,9)]; |
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119 %! assert(fftfilt(b, x ), [1 1 0 0 0 0 0 0 0 0] , eps); |
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120 %! assert(fftfilt(b, x.'), [1 1 0 0 0 0 0 0 0 0].', eps); |
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121 %! assert(fftfilt(b.',x ), [1 1 0 0 0 0 0 0 0 0] , eps); |
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122 %! assert(fftfilt(b.',x.'), [1 1 0 0 0 0 0 0 0 0].', eps); |
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123 |
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124 %!test |
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125 %! r = sqrt(1/2) * (1+i); |
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126 %! b = b*r; |
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127 %! assert(fftfilt(b, x ), r*[1 1 0 0 0 0 0 0 0 0] , eps); |
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128 %! assert(fftfilt(b, r*x), r*r*[1 1 0 0 0 0 0 0 0 0], eps); |
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129 %! assert(fftfilt(b, x.'), r*[1 1 0 0 0 0 0 0 0 0].', eps); |
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130 |
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131 %!test |
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132 %! b = [1 1]; |
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133 %! x = zeros (10,3); x(1,1)=-1; x(1,2)=1; |
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134 %! y0 = zeros (10,3); y0(1:2,1)=-1; y0(1:2,2)=1; |
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135 %! y = fftfilt (b, x); |
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136 %! assert (y,y0); |
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137 |
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138 %!test |
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139 %! b = rand (10, 1); |
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140 %! x = rand (10, 1); |
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141 %! y0 = filter (b, 1, x); |
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142 %! y = filter (b, 1, x); |
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143 %! assert (y, y0); |
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144 |
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145 %% Test input validation |
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146 %!error fftfilt (1) |
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147 %!error fftfilt (1, 2, 3, 4) |
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148 %!error fftfilt (ones (2), 1) |
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149 %!error fftfilt (2, ones (3,3,3)) |
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150 %!error fftfilt (2, 1, ones (2)) |
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151 |