Re: [Discuss-gnuradio] Re: Multiplying blocks

[Eric Blossom]

On Fri, Jun 09, 2006 at 03:58:58PM -0700, Johnathan Corgan wrote:
> Eric Blossom wrote:
> 
> The application here is to multiply an incoming stream of floats by an
> analysis window and pass it off for further vector processing, and
> ultimately send it through an FFT block.  For example, google WOLA DFT
> or check this link:
> 
> http://www.epn-online.com/page/15837/efficient-digital-channelisers-for-fpgas-mixed-radix-fft-designs.html
> 
> and specifically the diagram here:
> 
>
> http://www.epn-online.com/common/inc/loadimage.php?name=33/10/G-09946C.JPG

OK.

Here's how I think you could do it without any new code (admittedly
it's a bit ugly): 

Use vector_source_f to provide your window, and set the repeat argument to True.

Before using stream_to_vector on the data, mulitply by the repeating
window using

  gr.multiply_ff (or _cc as the case may be)

The run the output of that into gr.stream_to_vector



> > One idea has been to use the "Universal function" (ufunc) idea from
> > NumPy and Numeric:
> 
> Yes, your example would work nicely for what I think is needed.
> 
> > Are you interested in building something along these lines?
> > It would be a *very* useful contribution.
> 
> I might be interested but every time I try to understand what you're
> doing with SWIG to bridge the C++ and Python worlds, I get a serious
> migraine (that's over and above the minor headache stemming from
> deciphering the autotools) :-)

Oh come on, it's not that hairy ;)

Mostly the SWIG .i file is a subset of the .h file. 
Just add the GNURADIO_SWIG_BLOCK_MAGIC call at the top ;)

As long as your constructor and methods arguments are ints,
longs, floats, gr_complex or std::vector<foo> of them, pretty much
everything just works.  If you've got questions, just ask.

Regarding the autotools:  Mostly you've just got to add 3 lines to
the existing Makefile.am.  One each for the .h, .cc and .i file.

There's the also the "How to write a block" article.  It walks you through
building an extension outside of gnuradio-core.
http://www.gnu.org/software/gnuradio/doc/howto-write-a-block.html

> -Johnathan, AE6HO

Eric