3 * Copyright 2010 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
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15 * GNU General Public License for more details.
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19 * the Free Software Foundation, Inc., 51 Franklin Street,
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27 #include <gri_fft_filter_fff.h>
33 gri_fft_filter_fff::gri_fft_filter_fff (int decimation, const std::vector<float> &taps)
34 : d_fftsize(-1), d_decimation(decimation), d_fwdfft(0), d_invfft(0)
39 gri_fft_filter_fff::~gri_fft_filter_fff ()
46 * determines d_ntaps, d_nsamples, d_fftsize, d_xformed_taps
49 gri_fft_filter_fff::set_taps (const std::vector<float> &taps)
52 compute_sizes(taps.size());
54 d_tail.resize(tailsize());
55 for (i = 0; i < tailsize(); i++)
58 float *in = d_fwdfft->get_inbuf();
59 gr_complex *out = d_fwdfft->get_outbuf();
61 float scale = 1.0 / d_fftsize;
63 // Compute forward xform of taps.
64 // Copy taps into first ntaps slots, then pad with zeros
65 for (i = 0; i < d_ntaps; i++)
66 in[i] = taps[i] * scale;
68 for (; i < d_fftsize; i++)
71 d_fwdfft->execute(); // do the xform
73 // now copy output to d_xformed_taps
74 for (i = 0; i < d_fftsize/2+1; i++)
75 d_xformed_taps[i] = out[i];
80 // determine and set d_ntaps, d_nsamples, d_fftsize
83 gri_fft_filter_fff::compute_sizes(int ntaps)
85 int old_fftsize = d_fftsize;
87 d_fftsize = (int) (2 * pow(2.0, ceil(log(ntaps) / log(2))));
88 d_nsamples = d_fftsize - d_ntaps + 1;
91 fprintf(stderr, "gri_fft_filter_fff: ntaps = %d, fftsize = %d, nsamples = %d\n",
92 d_ntaps, d_fftsize, d_nsamples);
94 assert(d_fftsize == d_ntaps + d_nsamples -1 );
96 if (d_fftsize != old_fftsize){ // compute new plans
99 d_fwdfft = new gri_fft_real_fwd(d_fftsize);
100 d_invfft = new gri_fft_real_rev(d_fftsize);
101 d_xformed_taps.resize(d_fftsize/2+1);
106 gri_fft_filter_fff::filter (int nitems, const float *input, float *output)
110 int ninput_items = nitems * d_decimation;
112 for (int i = 0; i < ninput_items; i += d_nsamples){
114 memcpy(d_fwdfft->get_inbuf(), &input[i], d_nsamples * sizeof(float));
116 for (j = d_nsamples; j < d_fftsize; j++)
117 d_fwdfft->get_inbuf()[j] = 0;
119 d_fwdfft->execute(); // compute fwd xform
121 gr_complex *a = d_fwdfft->get_outbuf();
122 gr_complex *b = &d_xformed_taps[0];
123 gr_complex *c = d_invfft->get_inbuf();
125 for (j = 0; j < d_fftsize/2+1; j++) // filter in the freq domain
128 d_invfft->execute(); // compute inv xform
130 // add in the overlapping tail
132 for (j = 0; j < tailsize(); j++)
133 d_invfft->get_outbuf()[j] += d_tail[j];
135 // copy nsamples to output
137 //memcpy(out, d_invfft->get_outbuf(), d_nsamples * sizeof(float));
141 while (j < d_nsamples) {
142 *output++ = d_invfft->get_outbuf()[j];
145 dec_ctr = (j - d_nsamples);
148 memcpy(&d_tail[0], d_invfft->get_outbuf() + d_nsamples,
149 tailsize() * sizeof(float));
152 assert(dec_ctr == 0);