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48 lines
1.5 KiB
C++
48 lines
1.5 KiB
C++
/**
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* 2_convolve_overlap_save.cpp
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* Written by Clyne Sullivan.
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*
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* This convolution examples takes an overlap-save approach, where samples from the previous run
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* are saved so that the overall operation is not interrupted (i.e. the observed output will
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* transition smoothly between processed "chunks").
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*
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* Note that there are still improvements that can be made to the code; for example, notice every
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* spot where an integer/float conversion is necessary. Operations like these may slow down the
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* computation.
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*/
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adcsample_t *process_data(adcsample_t *samples, unsigned int size)
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{
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static adcsample_t buffer[SIZE];
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constexpr unsigned int filter_size = 3;
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float filter[filter_size] = {
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0.3333, 0.3333, 0.3333
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};
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// Keep a buffer of extra samples for overlap-save
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static adcsample_t prev[filter_size];
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for (int n = 0; n < size; n++) {
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buffer[n] = 0;
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for (int k = 0; k < filter_size; k++) {
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int i = n - (filter_size - 1) + k;
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// If i is >= 0, access current sample buffer.
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// If i is < 0, provide the previous samples from the 'prev' buffer
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if (i >= 0)
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buffer[n] += samples[i] * filter[k];
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else
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buffer[n] += prev[filter_size - 1 + i] * filter[k];
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}
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}
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// Save samples for the next convolution run
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for (int i = 0; i < filter_size; i++)
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prev[i] = samples[size - filter_size + i];
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return buffer;
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}
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