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Re: [Discuss-gnuradio] oprofile callgraph question

From: Charles Swiger
Subject: Re: [Discuss-gnuradio] oprofile callgraph question
Date: Sun, 22 Jun 2008 08:03:20 -0400

On Sat, 2008-06-21 at 11:07 -0700, Eric Blossom wrote:
> On Sat, Jun 21, 2008 at 11:01:22AM -0400, Charles Swiger wrote:
> > the bit_timing_loop for 16MHz? I'll check in what I have
> Please do this on a branch.


> > static const double     BANDWIDTH = 0.25;
> > 
> You're still basically hosed if you leave BANDWIDTH at 0.25.
> Our bandwidth of interest is 6MHz (TV channel) and you want to run at
> 16MHz, you'd need it to be 0.375. 

Oh, so *thats* what it means! (Remember the thing about frequency in
radians/sample ;)

>  With regard to NTAPS, you'd want to
> look at the error between the ideal and actual transfer function over
> the frequency range of interest.  IIRC the code in gen_interpolator_taps
> computes this as its metric.  Keep NTAPS a a multiple of 4 since the
> SIMD code is going to round it up to that anyway (padding with zeros).
> Didn't you try the J.O. Smith resampler?  How did that work out?

Yes - I make a block called gr_samplerate_ff linked against Erik de
Castro's libsamplerate and it worked fine with audio - dial tone at
bizzare sample rates came out sounding normal to the ear - but it just
did not work for the bit_timing_loop. What with 1) an external
dependancy, 2) it would use up to 25% cpu just at audio rates on a
1.5Ghz Pentium-M, I just moved on to trying new taps for your existing
fractional resampler.


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