RE: [Discuss-gnuradio] fractional_interpolator_cc?

[Clark Pope]

I think I just figured it out: The actual interpolation is 1/ the value you feed it. I assumed the second parm was to be the interpolation factor but looking at the .cc file I see it's inverted internally. If I put in 0.5 I get twice the output like I expect. (Tried this previously but it threw an error somewhere else which I mistakenly thought meant the interp parm had to be >=1). Thanks

> Date: Tue, 21 Oct 2008 10:34:14 -0400
> From: address@hidden
> To: address@hidden
> Subject: Re: [Discuss-gnuradio] fractional_interpolator_cc?
> CC: address@hidden
>
> On Tue, Oct 21, 2008 at 10:15 AM, Clark Pope <address@hidden> wrote:
> >
> > I'm not able to get this function to work correctly. I have it just connected between a snapshot file and an output file. I set the interpolation factor to 2.0 and the output file ends up half the size of the input file. It's like it is a decimation block instead of interpolation?
>
> How does the rational resampler work out - or can you not represent
> the ratio as a rational number?
>
> Are you calling it correctly? It seems as if there is a phase shift
> as well as an interpolation ratio being passed in.
>
> http://gnuradio.org/trac/browser/gnuradio/trunk/gnuradio-core/src/lib/filter/gr_fractional_interpolator_cc.cc#L38
> http://gnuradio.org/trac/browser/gnuradio/trunk/gnuradio-core/src/lib/filter/gr_fractional_interpolator_cc.cc#L67
>
> There may be an issue here:
>
> http://gnuradio.org/trac/browser/gnuradio/trunk/gnuradio-core/src/lib/filter/gr_fractional_interpolator_cc.cc#L49
>
> Might be upside down?
>
> Brian

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