[ntp:questions] Re: Where to obtain audioio.h

David L. Mills mills at udel.edu
Mon Sep 8 13:47:27 UTC 2003


Ross,

The various architectures are very different in how they treat the codec
driver and mixer. All I know is the Solaris mixer introduces 10 ms of
jitter and is so far undefeatable. I am told to connect directly to the
driver and avoid the mixer; but the kernel tricks to do that are
elusive. Before Solaris 8 the IRIG driver was good to about 10
microseconds jitter, now it has balooned to 10 milliseconds jitter. See
my comments in the refclock_irig.c driver. Apparently, the increase is
due to some aspect of the mixer I have not been able to defeat. I am not
the expert here, but somebody with a more serious mission should expand
on the ways to avoid this problem.

Ross wrote:
> 
> "David L. Mills" <mills at udel.edu> writes:
> 
> > Tim,
> >
> > Ouch, that must hurt a lot. Far better to hack ./libntp/audio.c and
> > leave the refclock_wwv.c alone. That makes the CHU and IRIG drivers work
> > as well. By the way, using the audio mixer with audio drivers is
> > strongly discouraged, as it introduces some nasty jitter.
> 
> Dear Dr. Mills,
> 
> I must be a little dense, because I can't imagine how you get the audio
> into the ADC without going through the mixer.  Could you expand a little
> on this for the benefit of the chimelorn?  FWIW, I've hacked upon the
> code a little myself, and a great deal of what needed work was precisely
> getting the mixers to fly right (FreeBSD w/ multiple radios environment).
> 
> regards,
> Ross ve6pdq
> --
> Ross Alexander
> (780) 975 3505 cell / (780) 433 6725 home
> ralexan9 at telusplanet.net



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