Re: Slow video

Roadkill On the Information SuperHighway! (warren@sniff.shr.dec.com)
Mon, 10 Mar 1997 14:39:24 -0500


Mark;

the "51,200" that you see is the DTE speed or the spped of the modem to PC bus.
What you really want is the speed that the two modems connect at or modem to
modem speed. To get this you need to change one of your modems reporting
parameters (usually ATW? for Hayes command language). Look up th "W" command
in your modems users guide. You can set it in your dialup networking connectionsince optional modem settings are looked at last by Win95. This will over-ride
the the default value.

But getting to the cause of your slow video.... it's due to the slow connection
speed which for you is actually 33.6kbps or less depending on what the two
modems negotiate at connection time. To get resonable refresh rates you will
need ISDN (both channels ~128kbps) at a minimum.

But wait...there's less! Don't give up because there are tricks to improve
your video experience. If your goal is point to point communication where
the other person is also on a modem you could try this.

Drop your maximum xmission rate down to 10 - 14 kbps. Use the audio
from a program called "SpeakFreely" (www.fourmilab.ch) and set the audio
compression to "GSM" and "SIMPLE." This drops your audio bandwidth down to
to the point where both your video from Cu-Seeme and audio from SpeakFreely
will fit within your total bandwidth. The advantage of this setup is the
audio is much more consistant and reliable the Cu-Seeme audio over a narrow
bandwidth connection.

Having done that your video will still be slow but the audio will
be perfect. Well,,,,perfect if you can't tell the difference between
Donald duck and Luciano Pavarotti. It's a far better thing to miss some
video frames then audio frames.

Other tricks to improve your video are: use dark stationary background;
don't move more then you hav to; make yourself smaller by positioning the
camera further away; use side lighting so only half your face is shown. In
general; the video frame is split up into small squares (8x8 pixels I believe)
and only the squares that change are sent. Hence; the less the scene changes
the less the bandwidth and the higher effective frame rate.

Finally; if you run out and buy your own T3 connection you can
forget about everything I just said. :-)

Warren

----------------------------- Cut Here --------------------------------

I'm hoping someone can give me some pointers on what may be the cause of
slow video on CU-SeeMe. I am consistently getting extremely low kbps
(1-5 range) and non-existent fps (rarely above 0). Other people on the
same reflector as I am tell me they're getting 5-10 kpbs (or more) and
sometimes up to 3-4 fps.

I'm running the White Pine version 2.1.1 under Windows 95. My computer
is a Pentium 200 with 32MB of RAM and a 33.6 modem. When I connect, the
dial-up networking says I'm connecting at 51,200.

I'm beginning to think it may just be my ISP that's slowing down the
process. I'm using AT&T Worldnet.