Re: problems with color and audio

John Ingham (johningh@tafe.sa.edu.au)
Thu, 27 Feb 1997 13:43:23 +0930


Dr. Bob said...

>I had a lot of trouble today connecting with someone else. I'm not sure if
>the problem was me, her, the reflector, bandwidth, some combination of the
>above, or what. I could use some help.

Where at all possible, for best results when using speech in a point to
point call, try to connect direct not via a reflector. By all means use a
reflector as a meeting point to exchange IPs etc, but call direct as soon
as you can.

>It's the Cornell reflector, 4.00b3. I was using 0.87a1 on a 68040 Mac with
>an Ethernet connection. She was using 2.1.1x and Windows with a 33.6 modem.
>I had a basic quickcam, she had a color one.

It is my understanding that at this time Cornell Reflectors do not support
color. Therefore anyone attempting to transmit color will show as a Lurker.

>She showed up as a lurker, and that may just be the way it is (for now)
>with color. Or is there some way to get black and white video from a color
>quickcam?

Yes, she should just choose another codec under Video Preferences. She
should find one called "CU-SeeMe Grey Scale". (Note it is not enough
merely to switch off the color data bitstream as allowed by the White Pine
codec. She must choose "CU-SeeMe Grey Scale").

>At first, neither of us could hear the other. When I switched to delta-mod,
>she was able to hear me. Her bar would darken in the Participants list at
>times, so there seemed to be some recognition of her audio. I had my
>volumes all the way up.
>
>She said the Audio options she had were Digitalk, Voxware, and delta-mod.

The 68040 Macintosh doesn't have enough "horsepower" to run with either the
Digitalk or Voxware audio codecs so that is why you could only communicate
via Delta-mod. However, you need a very good path between you to get good
Delta-mod audio at 16 kbs. You both also need to freeze your transmit
video while transmitting Delta-mod audio when running over a 28,800 bps
modem. And even then you may be disappointed with the results.

Ordinarily I'd recommend running PowWow concurrently and using its
excellent speech capabilities but PowWow is not available for the Macintosh
platform and in any case you'd still need to freeze your transmit video
when speaking - it's just that PowWow degrades much more gracefully than
any CU-SeeMe audio I've ever heard.

>It looked as if her Send and Receive parameters were 10 and 56 and 10 and
>33. Mine were 10, 60, and 60 and 10 and 200.

You should both choose caps to suit the "lowest common denominator" ie her
modem. Also, just because a person is using a fast modem (ie 33.6 kbs)
doesn't mean that their connection is actually running at that speed.
Depending on a number of factors their real connection speed may be more
like 24,000 bps. If you choose too low a cap, all that will result is a
lower frame rate than other might be the case. But if you choose too high
a cap, you'll pay the penalty by sending and receiving broken up pictures.

I hope this sheds some light on your problem.

John Ingham
Supervisor, Technical Operations, CALS (Centre for Applied Learning Systems)
Adelaide Institute of TAFE (Training and Further Education)
GPO Box 1872 Adelaide South Australia 5001
Ph: +61 8 8207 8550 Fax: +61 8 8207 8552
Email: johningh@tafe.sa.edu.au
Web Site: http://www.tafe.sa.edu.au/video-conf/
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