Re: [Discuss-gnuradio] How to make an FFT block in c++
On Fri, Oct 18, 2013 at 10:05 PM, Tommy Tracy II wrote: > Hello, > > I'm trying to make an FFT block in my hierarchical block, but I cannot seem > to find the correct syntax. > I'm trying to make it with a BLACKMAN_HARRIS windowing function, and it's > easy in a python program: > > fft_forward = fft.fft_vfc(window_size, True, > (fft.blackmanharris(window_size)), 1) > fft_backward = fft.fft_vcc(window_size, False, > (fft.blackmanharris(window_size)), False, 1) > > > But in a c++ program it gets hairy. Does anyone have any experience with > this? > > gr::fft::fft_vfc::sptr fft_forward = gr::fft::fft_vfc::make(SIZE, true, > gr::filter::firdes::WIN_BLACKMAN_HARRIS, num_threads); > gr::fft::fft:vcc::sptr fft_reverse = gr::fft::fft_vcc::make(SIZE, false, > gr::filter::firdes::WIN_BLACKMAN_HARRIS, false, num_threads); > > I believe what I have wrong is the Windowing, which is of the form: > > const std::vector< float > & window I have only used gr::fft::fft_complex in C++ but I think it uses the same window type. If that's true you can create the window using: window = gr::filter::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, SIZE, 6.76); Alex ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] How to make an FFT block in c++
Thanks a lot. I do have a question about the 6.67 that you pass to the gr::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, SIZE, 6.67); What is the importance of this value? Is this the default BETA? I found that when creating a BLACKMANHARRIS window in python and c++, I got two different results. Sincerely, Tommy James Tracy II Ph.D Student High Performance Low Power Lab University of Virginia Phone: 913-775-2241 On Oct 18, 2013, at 5:20 PM, Alexandru Csete wrote: > On Fri, Oct 18, 2013 at 10:05 PM, Tommy Tracy II wrote: >> Hello, >> >> I'm trying to make an FFT block in my hierarchical block, but I cannot seem >> to find the correct syntax. >> I'm trying to make it with a BLACKMAN_HARRIS windowing function, and it's >> easy in a python program: >> >>fft_forward = fft.fft_vfc(window_size, True, >> (fft.blackmanharris(window_size)), 1) >>fft_backward = fft.fft_vcc(window_size, False, >> (fft.blackmanharris(window_size)), False, 1) >> >> >> But in a c++ program it gets hairy. Does anyone have any experience with >> this? >> >>gr::fft::fft_vfc::sptr fft_forward = gr::fft::fft_vfc::make(SIZE, true, >> gr::filter::firdes::WIN_BLACKMAN_HARRIS, num_threads); >>gr::fft::fft:vcc::sptr fft_reverse = gr::fft::fft_vcc::make(SIZE, false, >> gr::filter::firdes::WIN_BLACKMAN_HARRIS, false, num_threads); >> >> I believe what I have wrong is the Windowing, which is of the form: >> >>const std::vector< float > & window > > I have only used gr::fft::fft_complex in C++ but I think it uses the > same window type. If that's true you can create the window using: > > window = gr::filter::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, > SIZE, 6.76); > > Alex ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] How to make an FFT block in c++
On Fri, Nov 1, 2013 at 6:16 AM, Tommy Tracy II wrote: > Thanks a lot. I do have a question about the 6.67 that you pass to the > gr::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, SIZE, 6.67); > > What is the importance of this value? Is this the default BETA? I found that > when creating a BLACKMANHARRIS window in python and c++, I got two different > results. If I recall correctly that parameter is only used for the Kaiser window and not for the others. Alex ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] How to make an FFT block in c++
You’re right; the following syntax is the least ambiguous for creating Blackmanharris windows in c++: const std::vector< float > fft_window = gr::filter::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, 1024, NULL); Sincerely, Tommy James Tracy II Ph.D Student High Performance Low Power Lab University of Virginia Phone: 913-775-2241 On Nov 1, 2013, at 6:04 AM, Alexandru Csete wrote: > On Fri, Nov 1, 2013 at 6:16 AM, Tommy Tracy II wrote: >> Thanks a lot. I do have a question about the 6.67 that you pass to the >> gr::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, SIZE, 6.67); >> >> What is the importance of this value? Is this the default BETA? I found that >> when creating a BLACKMANHARRIS window in python and c++, I got two different >> results. > > If I recall correctly that parameter is only used for the Kaiser > window and not for the others. > > Alex signature.asc Description: Message signed with OpenPGP using GPGMail ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] How to make an FFT block in c++
On Fri, Nov 1, 2013 at 4:42 PM, Tommy Tracy II wrote: > You’re right; the following syntax is the least ambiguous for creating > Blackmanharris windows in c++: > > const std::vector< float > fft_window = > gr::filter::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, 1024, > NULL); I'm actually going to update that to have a default argument for beta, so you don't even need to set anything if you aren't using a Kaiser window. Tom > Sincerely, > Tommy James Tracy II > Ph.D Student > High Performance Low Power Lab > University of Virginia > Phone: 913-775-2241 > > On Nov 1, 2013, at 6:04 AM, Alexandru Csete wrote: > > On Fri, Nov 1, 2013 at 6:16 AM, Tommy Tracy II wrote: > > Thanks a lot. I do have a question about the 6.67 that you pass to the > gr::firdes::window(gr::filter::firdes::WIN_BLACKMAN_HARRIS, SIZE, 6.67); > > What is the importance of this value? Is this the default BETA? I found that > when creating a BLACKMANHARRIS window in python and c++, I got two different > results. > > > If I recall correctly that parameter is only used for the Kaiser > window and not for the others. > > Alex > > > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
