Re: [Discuss-gnuradio] Bug in fmdet_cf_imp.cc

[CEL]

Hello Eugene,

Thanks! I.. uh. wat?! There's a lot of interesting things in the code
of that block. d_8 being a constant with value 8 not being the largest
surprise; I see that this should be a derivative-approximating filter,
right, which inherently needs to have high-pass characteristics, and
honestly, odd symmetry would be good, so yeah, without knowing what
exactly I'm looking at here, it seems this is the right thing to do.
Can you point me at the source for the Taylor series (it looks like
one) you're citing in your last email?

Taking a step back, Sdot is really just the result of a FIR filter
applied to the input signal, isn't it? So, let's add that to the list
of things to actually use VOLK on to speed things up.

Best regards,
Marcus

On Fri, 2018-06-08 at 18:48 +0000, Eugene Grayver wrote:
> Hello,
>  
> There is a bug in the FM demod.  Unbelievably (almost), I reported a
> bug in the same line a couple of years ago.  At that time I also
> goofed (should have not retyped it).  The equation is STILL wrong!
>  
> Sdot = d_scl * (-S0+d_8*S1-d_8*S2+S4);
>  
> Should be
>  
> Sdot = d_scl * (-S0+d_8*S1-d_8*S3+S4);
>  
>  
> 
>  
> It is crazy that the basic FM demo works at all.
>  
>  
> _______________________
> Eugene Grayver, Ph.D.
> Aerospace Corp., Sr. Eng. Spec.
> Tel: 310.336.1274
> ________________________
>  
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

smime.p7s
Description: S/MIME cryptographic signature