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## Re: [Discuss-gnuradio] Modifying vectors

**From**: |
Patrick Strasser |

**Subject**: |
Re: [Discuss-gnuradio] Modifying vectors |

**Date**: |
Sun, 19 Mar 2006 22:53:28 +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 |

Eric Blossom wrote:

On Fri, Mar 17, 2006 at 10:27:45AM +0100, Patrick Strasser wrote:

Hello!
fft = gr.fft_vfc(fft_size, True, window.hanning(fft_size))
ifft = gr.fft_vcc(fft_size, False, window.hanning(fft_size))
self.connect(s2p, fft )
self.connect(fft, ifft )
self.connect(ifft, p2s )

>>

now I want to modify data between fft and ifft.
Do I have to make a custom block in python (I'd like to do this anyway...)?

Depends on what you want to do. A few of the blocks support an
optional "vlen" constructor argument. These will apply the given
operation to a vector of items.
If for example you want to independently filter the bins, you could
use gr.stream_to_streams, a bunch of filter blocks, then
gr.streams_to_stream. See

`gnuradio-core/src/python/gnuradio/blksimpl/filterbank.py
`

So you can use these blocks with vectors of that type too. Clever shortcut!

`No, I want to interpolate between the bins. I want to modify the
``spextrum. I know there is at least one other way (resampling), but this
``is the most straight forward way for me.
`

This isn't completely sorted out. Besides adding the "vlen" attribute
to many blocks, we've also considered using a Numeric / NumPy / SciPy
"ufunc" (universal function) mechanism and then a small number of
GNU Radio blocks that know how to apply ufuncs across streams.
"ufuncs" would probably be easier to write in the common cases than
full GNU Radio blocks.

And a ufunc would be able to modify the stream on the fly?
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