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

On 1/30/14, keenerd <keenerd@gmail.com> wrote:
> On 1/30/14, Anders Lynge Esbensen <anders@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