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Re: [Discuss-gnuradio] Fractional Resampler discards samples
From: |
Andrej Rode |
Subject: |
Re: [Discuss-gnuradio] Fractional Resampler discards samples |
Date: |
Thu, 04 Feb 2016 10:38:28 +0100 |
User-agent: |
KMail/4.14.10 (Linux/4.1.15-gentoo-r1; KDE/4.14.16; x86_64; ; ) |
Thanks for the reply
> 03.02.2016 22:36, Andrej Rode wrote:
> > (with a resampling rate of 1 and a phase offset) also
>
> I presume that's "... and a ZERO phase offset", right?
Yes, you guessed right somehow I left the word zero out.
> So I used the source, Luke, and
>
> 1. these are not the resamplers you're looking for (probably), unless
> you're really going for non-rational ($\frac1\pi$) or really
> really-close-to-1 ratios, and
> 2. the point where the phase delay is implemented is by using the MMSE
> interpolator[1], which really is just a set of FIRs, from which the
> right one is selected by definition of the µ to use.
I have not selected this resampler by myself and just recognised some weird
behaviour in the channel model block.
I have just ran some tests and it seems there is not just a delay:
(again resampling rate=1.0 phase offset=0)
First five input samples:
[(1+0j), (0.9980267284282716+0.06279051952931337j),
(0.9921147013144779+0.12533323356430426j),
(0.9822872507286887+0.18738131458572463j),
(0.9685831611286311+0.2486898871648548j)]
First five output samples:
((0.9822872281074524+0.187381312251091j),
(0.9685831665992737+0.24868988990783691j),
(0.9510565400123596+0.30901700258255005j),
(0.9297764897346497+0.3681245446205139j),
(0.9048270583152771+0.4257792830467224j))
A delay would be something I expect but completely removing samples? Is it
possible the first 3 samples are used to initialize the filter? Maybe I can
also dig through the source but not until evening.
Regards,
Andrej
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