3 * Copyright 2009 Free Software Foundation, Inc.
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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>
32 gr_pfb_arb_resampler_ccf_sptr gr_make_pfb_arb_resampler_ccf (float rate,
33 const std::vector<float> &taps,
34 unsigned int filter_size)
36 return gr_pfb_arb_resampler_ccf_sptr (new gr_pfb_arb_resampler_ccf (rate, taps,
41 gr_pfb_arb_resampler_ccf::gr_pfb_arb_resampler_ccf (float rate,
42 const std::vector<float> &taps,
43 unsigned int filter_size)
44 : gr_block ("pfb_arb_resampler_ccf",
45 gr_make_io_signature (1, 1, sizeof(gr_complex)),
46 gr_make_io_signature (1, 1, sizeof(gr_complex))),
49 /* The number of filters is specified by the user as the filter size;
50 this is also the interpolation rate of the filter. We use it and the
51 rate provided to determine the decimation rate. This acts as a
52 rational resampler. The flt_rate is calculated as the residual
53 between the integer decimation rate and the real decimation rate and
54 will be used to determine to interpolation point of the resampling
57 d_int_rate = filter_size;
58 d_dec_rate = (unsigned int)floor(d_int_rate/rate);
59 d_flt_rate = (d_int_rate/rate) - d_dec_rate;
61 // The accumulator keeps track of overflow to increment the stride correctly.
64 // Store the last filter between calls to work
67 d_filters = std::vector<gr_fir_ccf*>(d_int_rate);
69 // Create an FIR filter for each channel and zero out the taps
70 std::vector<float> vtaps(0, d_int_rate);
71 for(unsigned int i = 0; i < d_int_rate; i++) {
72 d_filters[i] = gr_fir_util::create_gr_fir_ccf(vtaps);
75 // Now, actually set the filters' taps
79 gr_pfb_arb_resampler_ccf::~gr_pfb_arb_resampler_ccf ()
81 for(unsigned int i = 0; i < d_int_rate; i++) {
87 gr_pfb_arb_resampler_ccf::set_taps (const std::vector<float> &taps)
91 unsigned int ntaps = taps.size();
92 d_taps_per_filter = (unsigned int)ceil((double)ntaps/(double)d_int_rate);
94 // Create d_numchan vectors to store each channel's taps
95 d_taps.resize(d_int_rate);
97 // Make a vector of the taps plus fill it out with 0's to fill
98 // each polyphase filter with exactly d_taps_per_filter
99 std::vector<float> tmp_taps;
101 while((float)(tmp_taps.size()) < d_int_rate*d_taps_per_filter) {
102 tmp_taps.push_back(0.0);
105 // Partition the filter
106 for(i = 0; i < d_int_rate; i++) {
107 // Each channel uses all d_taps_per_filter with 0's if not enough taps to fill out
108 d_taps[i] = std::vector<float>(d_taps_per_filter, 0);
109 for(j = 0; j < d_taps_per_filter; j++) {
110 d_taps[i][j] = tmp_taps[i + j*d_int_rate]; // add taps to channels in reverse order
113 // Build a filter for each channel and add it's taps to it
114 d_filters[i]->set_taps(d_taps[i]);
117 // Set the history to ensure enough input items for each filter
118 set_history (d_taps_per_filter);
124 gr_pfb_arb_resampler_ccf::print_taps()
127 for(i = 0; i < d_int_rate; i++) {
128 printf("filter[%d]: [", i);
129 for(j = 0; j < d_taps_per_filter; j++) {
130 printf(" %.4e", d_taps[i][j]);
137 gr_pfb_arb_resampler_ccf::general_work (int noutput_items,
138 gr_vector_int &ninput_items,
139 gr_vector_const_void_star &input_items,
140 gr_vector_void_star &output_items)
142 gr_complex *in = (gr_complex *) input_items[0];
143 gr_complex *out = (gr_complex *) output_items[0];
147 return 0; // history requirements may have changed.
150 int i = 0, j, count = 0;
153 // Restore the last filter position
156 // produce output as long as we can and there are enough input samples
157 while((i < noutput_items) && (count < ninput_items[0]-1)) {
159 // start j by wrapping around mod the number of channels
160 while((j < d_int_rate) && (i < noutput_items)) {
161 // Take the current filter output
162 o0 = d_filters[j]->filter(&in[count]);
164 // Take the next filter output; wrap around to 0 if necessary
165 if(j+1 == d_int_rate)
166 // Use the sample of the next input item through the first filter
167 o1 = d_filters[0]->filter(&in[count+1]);
169 // Use the sample from the current input item through the nex filter
170 o1 = d_filters[j+1]->filter(&in[count]);
173 //out[i] = o0; // nearest-neighbor approach
174 out[i] = o0 + (o1 - o0)*d_acc; // linearly interpolate between samples
177 // Accumulate the position in the stream for the interpolated point.
178 // If it goes above 1, roll around to zero and increment the stride
179 // length this time by the decimation rate plus 1 for the increment
180 // due to the acculated position.
182 j += d_dec_rate + (int)floor(d_acc);
183 d_acc = fmodf(d_acc, 1.0);
185 if(i < noutput_items) { // keep state for next entry
186 count++; // we have fully consumed another input
187 j = j % d_int_rate; // roll filter around
191 // Store the current filter position