You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
48 lines
1.5 KiB
C++
48 lines
1.5 KiB
C++
4 years ago
|
/**
|
||
|
|
* 2_convolve_overlap_save.cpp
|
||
|
|
* Written by Clyne Sullivan.
|
||
|
|
*
|
||
|
|
* This convolution examples takes an overlap-save approach, where samples from the previous run
|
||
|
|
* are saved so that the overall operation is not interrupted (i.e. the observed output will
|
||
|
|
* transition smoothly between processed "chunks").
|
||
|
|
*
|
||
|
|
* Note that there are still improvements that can be made to the code; for example, notice every
|
||
|
|
* spot where an integer/float conversion is necessary. Operations like these may slow down the
|
||
|
|
* computation.
|
||
|
|
*/
|
||
|
|
|
||
|
|
adcsample_t *process_data(adcsample_t *samples, unsigned int size)
|
||
|
|
{
|
||
|
|
static adcsample_t buffer[SIZE];
|
||
|
|
|
||
|
|
constexpr unsigned int filter_size = 3;
|
||
|
|
float filter[filter_size] = {
|
||
|
|
0.3333, 0.3333, 0.3333
|
||
|
|
};
|
||
|
|
|
||
|
|
// Keep a buffer of extra samples for overlap-save
|
||
|
|
static adcsample_t prev[filter_size];
|
||
|
|
|
||
|
|
for (int n = 0; n < size; n++) {
|
||
|
|
buffer[n] = 0;
|
||
|
|
|
||
|
|
for (int k = 0; k < filter_size; k++) {
|
||
|
|
int i = n - (filter_size - 1) + k;
|
||
|
|
|
||
|
|
// If i is >= 0, access current sample buffer.
|
||
|
|
// If i is < 0, provide the previous samples from the 'prev' buffer
|
||
|
|
if (i >= 0)
|
||
|
|
buffer[n] += samples[i] * filter[k];
|
||
|
|
else
|
||
|
|
buffer[n] += prev[filter_size - 1 + i] * filter[k];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Save samples for the next convolution run
|
||
|
|
for (int i = 0; i < filter_size; i++)
|
||
|
|
prev[i] = samples[size - filter_size + i];
|
||
|
|
|
||
|
|
return buffer;
|
||
|
|
}
|
||
|
|
|