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Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work
From: |
Fons Adriaensen |
Subject: |
Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work |
Date: |
Tue, 25 Oct 2016 21:21:17 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hi Marcus,
> sorry, please believe me, no-one meant to upset you. I'm a bit surprised
> you're taking this so personally!
I'm pretty sure nobody wanted to upset me ! But apparently nobody is
interested to make the Jack interface work as intended, not even its
author...
> Anyway, how do you estimate the sample rate offset? Buffer fillage
> derivative? As you said, the problem is not lacking a resampler (in
> fact, the GNU Radio PFB resamplers are almost too good for this), or the
> CPU to run it, but to know what your sound cards are doing...
See <http://kokkinizita.linuxaudio.org/papers/adapt-resamp-pres.pdf>
and <http://kokkinizita.linuxaudio.org/papers/adapt-resamp.pdf>
Between the two incoherent domains there is a buffer and a resampler.
The resampler is adjusted so that the average number of samples 'in
the pipeline' is constant. The problem is finding a reliable and
noise-free estimate of that number. At both ends we don't have a
clean continuous stream, but samples are written and read in blocks,
and the timing of those write and read operations can be irregular.
The solution is to have a delay-locked-loop (DLL) at either side
to remove measured timing jitter. This provides a continuous mapping
of time to the number of samples written and read. The difference
between the two is average number of samples in the buffer, which
is compared to a target value. The filtered difference then controls
the resampling ratio.
Ciao,
--
FA
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)
- [Discuss-gnuradio] simple mod-demod combinations doesn't work, MarkO, 2016/10/07
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Sylvain Munaut, 2016/10/08
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, MarkO, 2016/10/09
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Marcus Müller, 2016/10/09
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, MarkO, 2016/10/25
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Marcus Müller, 2016/10/25
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Fons Adriaensen, 2016/10/25
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Marcus Müller, 2016/10/25
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work,
Fons Adriaensen <=
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Kevin Reid, 2016/10/25
- [Discuss-gnuradio] Delay locked loop for the two-clock problem (was: simple mod-demod combinations doesn't work), Marcus Müller, 2016/10/26
- Re: [Discuss-gnuradio] Delay locked loop for the two-clock problem (was: simple mod-demod combinations doesn't work), Fons Adriaensen, 2016/10/26
- Re: [Discuss-gnuradio] Delay locked loop for the two-clock problem, Marcus Müller, 2016/10/26
- Re: [Discuss-gnuradio] Delay locked loop for the two-clock problem, Fons Adriaensen, 2016/10/27
- Re: [Discuss-gnuradio] Delay locked loop for the two-clock problem, Fons Adriaensen, 2016/10/27
- Re: [Discuss-gnuradio] Delay locked loop for the two-clock problem, Biju Ravindran, 2016/10/29
- Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work, Sylvain Munaut, 2016/10/25