[AG-TECH] Voyageur Recording

Lisa Childers childers at mcs.anl.gov
Fri Dec 14 09:33:40 CST 2001


Thanks for the reminder about time-synching.  Everyone in the community
should be running an NTP client on their audio and video machines.
Information on how to do this can be found at

The streams you see labeled "13 Flr Conference Rm" in the Finite Element
Analysis recording have unique ssrc's, which according to the RTP protocol
means they are independent video sources.  Since voyager demultiplexes media
data based on ssrc, they will appear in the stream list as multiple streams.

One possibility for the many streams is that the vic responsible for sending
"13 Flr Conference Rm" was relaunched several times during the recording.
Each time vic restarts a new ssrc is assigned to the stream.  However, a
quick look at the "duration" fields for these streams does not match that
scenario.  I am wondering if this phenomenon might be caused by buggy
multicast.  Perhaps Bill Nickless can chime in on the possibilities here.

The SCGlobal recordings from the showfloor voyager servers are being loaded
onto another voyager server and will be available to the community next
week.  The ones you see on the voyager.mcs.anl.gov server are a small
handful of the total SCGlobal set.

Congrats on the success of your finite element seminar!


-----Original Message-----
From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov]On
Behalf Of Don Morton
Sent: Friday, December 14, 2001 7:29 AM
To: Sergeant A. G. Tech
Subject: [AG-TECH] Voyageur Recording

I recall Mike Daw mentioning a problem on playback with
Voyageur and I tried it for the first time (well, the first
time by myself, without Lisa's supervision :).  I too ran
into problems but then noticed the "time offset" field
(or something like that) in the stream menu, and one site
was offset by over 5 seconds video and 43 seconds audio.
by unclicking those streams from the stream menu, i was
able to do a playback......  So, I know the importance
of time syncronisation has been preached to us but, this
is just a reminder to others who might try this that
one of the first things you might want to do when trying
to playback is "uncheque" the streams with large time
offsets so they don't mess you up.  BTW, I've notified
the "guilty party" about the time sync problem :) :)

Also (question for Lisa) - there were a BUNCH of streams
that said something like "13 Conference Room........ H.261..."
in the menu, then the "expected" streams from our actual
event.  Any idea where all those extras would have come
from?"  The specific event was from Windmer, 12 December,
"Don Morton (Finite Element Analysis)".

Finally, I tried looking for some of our sessions from SC Global
but they seemed pretty incomplete and, in fact, I couldn't find
any of the sessions I participated in.  I can give specifics
to Lisa privately but, am I correct in assuming that a number
of the sessions didn't get recorded or preserved?


   Don Morton                   http://MRoCCS.cs.umt.edu/~morton/
   Department of Computer Science       The University of Montana
   Missoula, MT 59812 | Voice (406) 243-4975 | Fax (406) 243-5139

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