This sounds interesting - do you have any sample code? Can anybody explain the concept of "size" of an fft (Arg 1 of fft . fft_vcc ) comes into play if the output of that FFT generates as many samples as it receives?
----- Original Message ----- From: "John Malsbury" <jmalsbury.perso...@gmail.com> To: "Brad Hein" <k1...@comcast.net> Cc: "Martin Braun" <martin.br...@ettus.com>, discuss-gnuradio@gnu.org Sent: Friday, October 17, 2014 1:50:31 AM Subject: Re: [Discuss-gnuradio] help accessing fft bins in python script Sometimes when I want to grab samples and perform some periodic operation like CNR estimation, or fine-frequency estimation I sometimes use a vector_sink, and then two function probe blocks - one to read the data and one to reset it (yes I call the reset function from the function probe). This seems to work wonderfully for certain corner cases where a vector sink doesn't work well. And I mostly use this technique when I want to prototyping something quickly before writing a block. But am I asking for trouble with memory allocation issues??? Also, I was thinking, it would be good to have the option, either a block parameter or an overloaded function) to reset the vector_sink, each time .data() is called... I can code this up unless anyone thinks this functionality would lead to regressions. But I agree the vector sink block is much more convenient for FFTs... -John On Thu, Oct 16, 2014 at 5:37 PM, Brad Hein < k1...@comcast.net > wrote: Is there any way to access the fft bins from python without writing a custom block? From: "Martin Braun" < martin.br...@ettus.com > To: discuss-gnuradio@gnu.org Sent: Thursday, October 16, 2014 2:02:03 PM Subject: Re: [Discuss-gnuradio] help accessing fft bins in python script A very simple way would just be to write your block downstream of the FFT in Python. You can then operate on the vectors in the work function. M On 10/16/2014 07:44 PM, mle...@ripnet.com wrote: > The vector sink is for debugging only. Don't use it in production code, > because there's no convenient way to > > vacuum it out, so it grows without bound. > > > > When I've had this problem, I use a vector-probe block, and have a > function probe running at a couple of Hz, > > and then leverage the dependency-tree evaluator to have my own > function called with the result of the > > function probe. There are other ways, that's the one I personally > find most convenient. But there are message > > queues and sundry other methods as well. > > > > > > > > > > On 2014-10-16 13:36, Brad Hein wrote: > >> >> Using qa_fft.py for inspiration[1], I'm trying to feed a raw capture >> file into an fft of size 32 and then review the 32 fft bins at an >> instantaneous point in time[2]. I must be doing something wrong >> however because when I review the vector sink's data() method, it >> returns a rather large array (compared to the 32-element array I am >> expecting). data() seems to return an array with the same number of >> elements as samples fed into the fft. I just want an array of the 32 >> fft bins so I can calculate the relative power in the given band. >> >> Any help/pointers appreciated! >> Thanks >> >> >> [1] >> http://gnuradio.org/redmine/projects/gnuradio/repository/revisions/master/entry/gr-fft/python/fft/qa_fft.py >> >> >> [2] >> https://github.com/regulatre/grfun/blob/9dbbf676d2fea013787720273af0b419699c75a4/hello-fft/decodeDump162.py >> >> >> >> [Brad Hein] >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org <mailto: 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 > _______________________________________________ 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
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