[Discuss-gnuradio] Fractional resampling

Hi,

having looked at the current codebase, I find two resamplers suitable
for interpolation rates close to 1: gr_fractional_interpolator and
gr_pfb_arb_resampler. I can see the latter is newer.
Here some questions:

1) When would I use which one, or is gr_fractional_interpolator
simply older? I can tell they use different approaches (MMSE vs. linear
interpolation), but don't really know what to do with this
information :)

2) Concerning gr_fractional_interpolator: The first parameter, called
phase_shift in the block definition and is later on referred to as
'mu', seems to be an initial fractional delay. For an infinite
stream, why does this matter? It seems to be important, otherwise it
would not be the first argument of the block constructor (or is this
coincidence? If it's pretty much irrelevant, why not make it second
and then give it mu=0 as default value?)

3) Concerning gr_pfb_arb_resampler (I hope I've understood the code
correctly): This uses a PFB to get the sampling rate close to what we
want, and then linearly interpolates. Isn't this a bit inaccurate?
I'm afraid I haven't got Harris' book right here, so I can't check
the reference, but perhaps someone who's already used this resampler
can share some experience?

Thanks a lot for any answers! They'll be greatly appreciated.

Cheers,
MB
--
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

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Building 05.01
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Phone: +49 721 608-3790
Fax: +49 721 608-6071
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KIT -- University of the State of Baden-Württemberg and
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