[AG-TECH] AGN Audio Lip Sync

[Brian Corrie]

Hi Randy,

A restart of rat seems to fix the problem so I don't think it is a time
problem (no evidence of that mind you). Our situation doesn't drift like
Bob's though. We have used it for long periods of continuous time and it is
fine, but sometimes we will come in and there is a serious 3-5 second lag.
Restarting rat fixes it immediately and we do not have problems afterward...

Brian


> -----Original Message-----
> From: Randy Groves [mailto:randy.groves at boeing.com]
> Sent: Tuesday, September 16, 2003 11:36 AM
> To: ag-tech at mcs.anl.gov
> Subject: RE: [AG-TECH] AGN Audio Lip Sync
> 
> 
> How much, if any, would the local machine time vs. the remote 
> nodes' time 
> have to do with this?  Would it help to make sure that NTP is 
> running and 
> appropriately syncing the system time?
> 
> -randy
> 
> At 08:04 AM 9/16/2003, Brian Corrie wrote:
> >When a lip synch is noticed, always the first solution is to 
> restart rat. It
> >does tend to drift over time. The size of the drift in the 
> time you mention
> >seems rather large. That is a bit odd. We see this 
> occasionally if we leave
> >things on over long periods of time, but it is certainly not 
> consistent (we
> >don't seem to degrade as a direct function of time).
> >
> >I am not sure why the sync slippage occurs (don't know 
> enough about rat/vic
> >and the RTP encoding) so I can't diagnose why you are seeing 
> what you see.
> >The only thing that pops into my head is that if there is 
> packet loss it may
> >have some impact (the protocols are supposed to handle that, 
> but...). Also,
> >computationally, if the vic or rat processing can't keep up 
> and falls behind
> >this may be the culprit. I can't remember if we see lag in 
> the video or in
> >the audio in our case. With UDP and RTP, one would think 
> that this would not
> >happen (you would just see packet loss instead) but again I 
> am not sure...
> >
> >That probably didn't help much did it 8-)
> >
> >Brian
> >
> >
> > > -----Original Message-----
> > > From: Wachtel, Robert L [mailto:Robert.Wachtel at mso.umt.edu]
> > > Sent: Tuesday, September 16, 2003 7:23 AM
> > > To: ag-tech at mcs.anl.gov
> > > Cc: Christensen, Scott A
> > > Subject: [AG-TECH] AGN Audio Lip Sync
> > >
> > >
> > > Are there any recommended solutions to the following audio video
> > > synchronization difficulty?
> > >
> > > Symptom: A progressively increasing sync delay between 
> the video and
> > > audio received from other sites within a venue. Lip sync 
> is very close
> > > when initially entering a venue, and then consistently 
> the audio is
> > > progressively delayed behind the video. After an hour 
> uptime we can
> > > notice a difference of up to 3 seconds. If we kill and
> > > restart just the
> > > rat, the sync will be restored and then begin slipping again.
> > >
> > > System:
> > > AGN 1.2
> > > Audio Box: Monarch AMD dual processor 4GB RAM, Creative 
> Audigy sound
> > > card, Red Hat Linux 7.3 OS
> > > Video Display: Monarch AMD dual processor 4GB RAM, Matrox 
> G450 x4 MMS
> > > quad head display card, Windows 2000 Pro OS
> > >
> > > Local Network:
> > > 100Mb Switched to desktop
> > > 1Gb Campus backbone
> > >
> > > Any suggested solutions or additional diagnostic measures would be
> > > appreciated.
> > >
> > > Thanks,
> > > Bob Wachtel
> > > Director
> > > Presentation Technology Services (PTS)
> > > The University of Montana
> > > Missoula, MT 59812
> > > Phone: 406-243-2857
> > > FAX: 406-243-2689
> > >
> 
> 
> 
>