I have a fundamental misunderstanding of the filter system in gnuradio. I would appreciate some help. I wrote a simple C++ testbench to help me figure out what's going on, but it continues to not behave as I expect. I am using fir_filter_fff with 29 taps that I set. I send an impulse into the filter and want to see the filter taps at the output in response. The first sample that comes out is correct, but every sample after the first is either the smallest or largest number representable by float. The code that does this is below.
float impulse[29] = {1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; // 29 samples long
float filter_taps[29] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1} // input to filter
shape_filter = new gr::filter::kernel::fir_filter_fff(1, filter_taps);
for(int i = 0; i < 29; i++) {
filter_out[i] = shape_filter->filter(&impulse[i]);
}
Printing filter_out to the screen produces:
0.1 0 8.12753e-44 1.61149e-43 -4.16205e-20 -8.32411e-20 -1.24862e-19 -1.66482e-19 1.13358e+21
You can see only the first output matches the expected.