3 * Copyright 2009 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
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27 #include <gr_pfb_arb_resampler_ccf.h>
28 #include <gr_fir_ccf.h>
29 #include <gr_fir_util.h>
30 #include <gr_io_signature.h>
33 gr_pfb_arb_resampler_ccf_sptr gr_make_pfb_arb_resampler_ccf (float rate,
34 const std::vector<float> &taps,
35 unsigned int filter_size)
37 return gr_pfb_arb_resampler_ccf_sptr (new gr_pfb_arb_resampler_ccf (rate, taps,
42 gr_pfb_arb_resampler_ccf::gr_pfb_arb_resampler_ccf (float rate,
43 const std::vector<float> &taps,
44 unsigned int filter_size)
45 : gr_block ("pfb_arb_resampler_ccf",
46 gr_make_io_signature (1, 1, sizeof(gr_complex)),
47 gr_make_io_signature (1, 1, sizeof(gr_complex))),
50 /* The number of filters is specified by the user as the filter size;
51 this is also the interpolation rate of the filter. We use it and the
52 rate provided to determine the decimation rate. This acts as a
53 rational resampler. The flt_rate is calculated as the residual
54 between the integer decimation rate and the real decimation rate and
55 will be used to determine to interpolation point of the resampling
58 d_int_rate = filter_size;
59 d_dec_rate = (unsigned int)floor(d_int_rate/rate);
60 d_flt_rate = (d_int_rate/rate) - d_dec_rate;
62 // The accumulator keeps track of overflow to increment the stride correctly.
65 // Store the last filter between calls to work
70 d_filters = std::vector<gr_fir_ccf*>(d_int_rate);
72 // Create an FIR filter for each channel and zero out the taps
73 std::vector<float> vtaps(0, d_int_rate);
74 for(unsigned int i = 0; i < d_int_rate; i++) {
75 d_filters[i] = gr_fir_util::create_gr_fir_ccf(vtaps);
78 // Now, actually set the filters' taps
82 gr_pfb_arb_resampler_ccf::~gr_pfb_arb_resampler_ccf ()
84 for(unsigned int i = 0; i < d_int_rate; i++) {
90 gr_pfb_arb_resampler_ccf::set_taps (const std::vector<float> &taps)
94 unsigned int ntaps = taps.size();
95 d_taps_per_filter = (unsigned int)ceil((double)ntaps/(double)d_int_rate);
97 // Create d_numchan vectors to store each channel's taps
98 d_taps.resize(d_int_rate);
100 // Make a vector of the taps plus fill it out with 0's to fill
101 // each polyphase filter with exactly d_taps_per_filter
102 std::vector<float> tmp_taps;
104 while((float)(tmp_taps.size()) < d_int_rate*d_taps_per_filter) {
105 tmp_taps.push_back(0.0);
108 // Partition the filter
109 for(i = 0; i < d_int_rate; i++) {
110 // Each channel uses all d_taps_per_filter with 0's if not enough taps to fill out
111 d_taps[i] = std::vector<float>(d_taps_per_filter, 0);
112 for(j = 0; j < d_taps_per_filter; j++) {
113 d_taps[i][j] = tmp_taps[i + j*d_int_rate]; // add taps to channels in reverse order
116 // Build a filter for each channel and add it's taps to it
117 d_filters[i]->set_taps(d_taps[i]);
120 // Set the history to ensure enough input items for each filter
121 set_history (d_taps_per_filter);
127 gr_pfb_arb_resampler_ccf::print_taps()
130 for(i = 0; i < d_int_rate; i++) {
131 printf("filter[%d]: [", i);
132 for(j = 0; j < d_taps_per_filter; j++) {
133 printf(" %.4e", d_taps[i][j]);
140 gr_pfb_arb_resampler_ccf::general_work (int noutput_items,
141 gr_vector_int &ninput_items,
142 gr_vector_const_void_star &input_items,
143 gr_vector_void_star &output_items)
145 gr_complex *in = (gr_complex *) input_items[0];
146 gr_complex *out = (gr_complex *) output_items[0];
150 return 0; // history requirements may have changed.
153 int i = 0, j, count = d_start_index;
156 // Restore the last filter position
159 // produce output as long as we can and there are enough input samples
160 while((i < noutput_items) && (count < ninput_items[0]-1)) {
162 // start j by wrapping around mod the number of channels
163 while((j < d_int_rate) && (i < noutput_items)) {
164 // Take the current filter output
165 o0 = d_filters[j]->filter(&in[count]);
167 // Take the next filter output; wrap around to 0 if necessary
168 if(j+1 == d_int_rate)
169 // Use the sample of the next input item through the first filter
170 o1 = d_filters[0]->filter(&in[count+1]);
172 // Use the sample from the current input item through the nex filter
173 o1 = d_filters[j+1]->filter(&in[count]);
176 //out[i] = o0; // nearest-neighbor approach
177 out[i] = o0 + (o1 - o0)*d_acc; // linearly interpolate between samples
180 // Accumulate the position in the stream for the interpolated point.
181 // If it goes above 1, roll around to zero and increment the stride
182 // length this time by the decimation rate plus 1 for the increment
183 // due to the acculated position.
185 j += d_dec_rate + (int)floor(d_acc);
186 d_acc = fmodf(d_acc, 1.0);
188 if(i < noutput_items) { // keep state for next entry
189 float ss = (int)(j / d_int_rate); // number of items to skip ahead by
190 count += ss; // we have fully consumed another input
191 j = j % d_int_rate; // roll filter around
195 // Store the current filter position and start of next sample
197 d_start_index = std::max(0, count - ninput_items[0]);
199 // consume all we've processed but no more than we can
200 consume_each(std::min(count, ninput_items[0]));