[AG-TECH] Audio losses synch (more technical questions)

White, Derek [NCSUS Non J&J] DWhite11 at NCSUS.JNJ.COM
Fri Jun 7 15:17:46 CDT 2002

I am assuming that the key for lip synch is that rat calculates the
end-to-end delay between encoding and final playback, and then rat sends
rtp.source.playout messages to the local vic. NTP is needed to get accurate
time differences. Vic can then adjust it's playback to match rat. 
This actually works to a point - vic gets the rtp.source.playout message,
but then can't figure out who the sender is! Vic looks through the
cname_hash_table, which is empty. Rat never sent an rtp.source.cname message
to any vic (it does send them to other rat processes though).
I tried a hack where vic sends an rtp.query message to all rats if it gets
an unknown rtp.source.playout message, which is a little too late, and rat
starts getting assertion failures soon after.
I'm not sure where the breakdown occurred. Should rat broadcast cname
messages to all vics on occasion? Should vic ask for cname at a better time?
 - Derek White
ps. This is with rat 4.2.16 built from cvs source. I spent a day trying to
get vic 2.8.ucl-1.1.3-AG to talk to rat 4.2.21, which is hopeless. The newer
mbus code does encryption and authentication in the opposite order, and over
a different part of the message! They silently refuse to talk at all.

-----Original Message-----
From: Nolan, Kevin [NCSUS] [mailto:knolan at ncsus.jnj.com] 
Sent: Friday, May 31, 2002 1:12 PM
To: ag-tech at accessgrid.org
Subject: [AG-TECH] Audio losses synch

I have a question -


We seem to lose synch with audio and video during sessions.  After several
hours of being up, the AG machines seem to fall into a 4 second audio delay
and not synchronize with video.   Is there a way to avoid this?




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