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[Discuss-gnuradio] serial_to_parallel and fft_v{f,c}c


From: Patrick Strasser
Subject: [Discuss-gnuradio] serial_to_parallel and fft_v{f,c}c
Date: Thu, 16 Mar 2006 21:45:05 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050602 Thunderbird/1.0.2 Mnenhy/0.7.2.0

Hello!

I'm playing arround, trying to do FFT.
Connecting some float source to fft_vfc did not work as flow_graph complains about "raise ValueError, 'source and destination data sizes are different'", which means that input data is not matching the input signature.

(BTW: With the Debian package when using fft_vfc with False as second argument for inverse FFT I get

fft_vfc: forward must == true
terminate called after throwing an instance of 'std::invalid_argument'
  what():  fft_vfc: forward must == true

With the current CVS-code I get

    return _gnuradio_swig_python.fft_vfc(*args)
TypeError: in method 'fft_vfc', argument 3 of type 'std::vector<float,std::allocator<float > > const'

I liked the old behaviour much more)

Back to topic:
From Chuck's FFT-example I could see i need some serial/parallel conversion. But I'm completely lost why this is needed as I don't understand all the magic behind the blocks and the different kinds of data that are pushed arround. So I'd be glad if someone could shed some light on the following:
What is serial_to_parallel doing?
Why is this needed?
Why vectors and not the usual block data?
What is the window flag (3rd parameter) in fft_v{f,c}c for?
What would be the best way to document all this in a nice end-user-compatible way? (I suppose users should be able to do their programming in python with some form of documentation that is _not_ C++ source code)

Patrick
--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at  tugraz dot at>
Student of Telematik, Techn. University Graz, Austria




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