Re: [Discuss-gnuradio] fft_filter_ccc Output Buffer Size

[Dave NotTelling]

After some more research it seems that this is an issue of not having an even multiple of input samples to taps.  For others, here is where I found the answer: http://www.dspguide.com/ch18/2.htm

On Fri, Feb 10, 2017 at 11:19 AM, Dave NotTelling <address@hidden> wrote:

I am trying to use the FFT filter in some c++ code and I'm having issues with seg faulting.  The code below will work, but only because the output buffer is twice as large as the input buffer.  It doesn't have to be twice as large, but it does have to be some number larger than the input buffer.  Why is that?  Also, how do I know what the output buffer size should be?

Thank you!!

[code]

#include <iostream>

#include <gnuradio/filter/fft_filter.h>

#include <complex>

#include <vector>

int main(){

    // Generate a set of zeroed out taps

    std::vector<std::complex<float> > taps(512, std::complex<float>(0.0f, 0.0f));

    // Number of random samples to generate

    const int sampleSize = 30000;

    // Create a vector of 32fc samples.  Don't initialize it to anything, just let it have

    // random data.

    gr_complex * input = (gr_complex *)malloc(sizeof(gr_complex) * sampleSize);

    // Place to store the output samples from the FFT

    gr_complex * output = (gr_complex *)malloc(sizeof(gr_complex) * sampleSize);

    // Create a filter to run the input samples through

    gr::filter::kernel::fft_filter_ccc * filter = new gr::filter::kernel::fft_filter_ccc(1, taps, 1);

    // Filter the input samples

    filter->filter(sampleSize, input, output);

    // Free up the malloc'd input and output storage

    free(input);

    free(output);

    delete filter;

    return 0;

}

[/code]