Re: Slow fps and no audio ?

Tim_Dorcey@cornell.edu
Sat, 2 Sep 1995 14:54:30 -0400


At 3:15 PM 9/1/95 -0500, Guido J. Deboeck OBPOD 80927 wrote:
>I installed CU-SeeMe0.80b1 on a PowerMac 8100/80, use a QuickCam and
>connect via a 128kpbs ISDN line. Nevertheless all connections I have made
>with colleagues at work (from home) provide max 4-5fps and no audio (the
>transmission is set at max & min 100 kbps. Anyone
>who can help ?

You ought to be able to do pretty decent point-to-point audio and video at
128 kbps. Are you sure you actually have 128 available, or might you have
only 64 for your data traffic?
In version 80b1, the kbps cap applies only to the video (and
Talk/Slide window) traffic, but not to audio. By setting your minimum
transmission rate to 100 kbps, you are saying to blast ahead with the video
at 100 kbps regardless of packet loss. Then, with the default audio
encoding at 32 kbps, you would be attempting to transmit around 132 kbps.
If you truly have 128 kbps available, you would expect a relatively small %
packet loss, and audio should be mostly intelligible. If, on the other
hand, you only have 64 kbps available your audio would be useless with 50%
loss.
I would recommend:

1) Set your minimum transmission rate to 10 kbps, so that CU-SeeMe can
attempt to find the capacity of the channel and not send more than it can
handle. I wouldn't be surprised if you see the cap drop from from 100 to
around 64. On the other hand, if you really do have > 100 kbps available,
having the minimum set to 10 should have no effect. Once you have
determined the capacity of the channel, you might want to set the maximum
kbps to something under that, to allow room for audio. This will not be
necessary in version 83, soon to be released, because video is
automatically throttled back whenever audio is outgoing.

2) Set your audio encoding method to 16 kbps delta-mod. This will degrade
the quality somewhat, but you will have a better chance of getting it
through.

3) Try increasing the "Change Tolerance" under the video Compression
settings. This should increase the frame rate for a given data rate. If
you set it too large, the quality will suffer. You need to experiment, as
the ideal setting depends upon the camera, digitizer, and lighting.

-Tim
__________________________________________________________________
Tim Dorcey Tim_Dorcey@cornell.edu
Sr. Programmer/Analyst (607) 255-5715
Advanced Technologies & Planning
CIT Network Resources
Cornell University
Ithaca, NY 14850
__________________________________________________________________