new FM demodulator

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Nikos Balkanas nikos.balkanas at eyeonix.com
Thu Jan 30 16:21:46 UTC 2014


On Thu, Jan 30, 2014 at 5:35 PM, keenerd <keenerd at gmail.com> wrote:

> On 1/30/14, keenerd <keenerd at gmail.com> wrote:
> > On 1/30/14, Anders Lynge Esbensen <anders at lyes.dk> wrote:
> >> I've implemented a faster FM demodulator for rlt_fm.
> >
> > Let me see if I can get a fixed-point version written.
>
> I've cleaned it up and it is in my repo.  You can enable it with "-A ale"
> https://github.com/keenerd/rtl-sdr/commit/025fb56dff98
>
> Some quick benchmarks:
> std: 10%
> fast: 7%
> lut: 7%
> ale: 7%
>
> Sound quality is also noticably worse with ale, but that might be from
> an error in the fixed point conversion.  How does the math look to
> you?
>

I have also be playing around with the atan demodulators. gnuradio uses
fast-atan tables instead of the libC version.
I dunno how libc implements it, but they could be worth considering...

Nikos



>
> -Kyle
> http://kmkeen.com
>
>
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