Re: fast connection, slow fps

Brad Klein (
Tue, 25 Feb 1997 13:39:10 -0800 (PST)

Hi John,

First of all, let me thank you, enthusiastically, for answering my post so
thouroghly. I am about to give up. Actually I have given up. The only
thing I am holding onto is this listserv in hopes of seeing a solution to
my problem.

> You say that you are"on a very crowded T1" - presumably via a LAN - but
> what network connection are YOU using on your 7100 Brad, Ethernet or
> Apple's Localtalk?

> And what are you comparing your results to - another
> CU-SeeMe user on the same LAN, or perhaps are your expectations based on
> dedicated Videoconferencing codecs or maybe on broadcast TV?
I cu with folks from within the same LAN, the same WAN and also across the
country. If I am within the same LAN or WAN the conferences are
moderatly acceptable. However, when I do a direct connection from here
(west coast, USA) to the east coast, either via a direct connection OR a
with our sun reflector, the fps is undetectable and the audio freeze
is non-existant.

> you are trying to run CU-SeeMe faster than your network connection you are
> bound to get lost packets and inferior results. With CU-SeeMe if you
> over-run your available bandwidth you will ALWAYS get degradation and
> poorer results than if you cap to within the available bandwidth.
Our available bandwidth is 1/3 T1. It leads into the WAN that ultimately
supports way too many educational users. I believe my real problem exists
at the WAN level. We are due for an upgrade soon.

Using Cornell v0.85b1, I used some specs from one of your postings back
on Jan. 2,'97, and set my recieve and transmit caps LOW,
"tranmission" min 5, max 10
"reception" min 5 max 60
"refresh interval" of 30
"change tolerance" of 40
Audio - 50ms and whatever mod I can get to work best, usually delta mod

> You say that your T1 is very crowded, and you quote 100 mhz or less. Quite
> a lot less actually because a T1 connection's maximum theoretical
> throughput is only about 1.5 million bits per second - nothing like 100 mhz
> (at the risk of comparing apples with oranges!) Even if you're running an
> Ethernet LAN connection, at (say) 100 kbs just one CU-SeeMe connection is
> taking up a sizable chunk of the available bandwith on an already "very
> crowded T1", and Ethernet is notorious for rapid degradation due to packet
> collisions as usage increases.
I do believe this is my problem. Until the upgrade goes through, I won't
be able to test this theory.

> It is some time ago that I did the test, but running my 7100/80av on an
> Ethernet with CU-SeeMe capped at 100 kbs gave reasonable quality results
> with sound in a point-to-point connection with someone on my own LAN. But
> it depends a lot on your expectations. I wasn't expecting to see
> full-screen, full 30 fps motion. What are you expecting to see?
If I could get a constant 4-6fps with audio I would be a happy camper. I
invariably get 1 or .5 or less with no audio.

In your Jan. mail you mentioned that "He who does not see(hear) a problem
is the most likely CAUSE of the problem." I can't help but think that this
fits me.

Thanks again.

Brad Klein
VolcanoWorld Online Education
Educational Service District 112, Vancouver, WA