Re: CU-SEEME Setup Optimization Guide

Mark Allard (mallard@mail.arc.nasa.gov)
Wed, 4 Dec 1996 09:27:44 -0800 (PST)


Here is some guidance on optimization of White Pine CU-SeeMe kindly
provided by the White Pine folks.
Hope it helps with various update rate annoyances,
M

These notes apply to Enhanced CU-SeeMe, v2.1.

Video Performance

Significant improvements in video performance levels can be achieved, by
ensuring that you correctly set up the codec settings, within the video
preferences. Most of the options shown below are within the Configure=8A
button on the Preferences screen. There is some element of experimentation
that may produce further improvements, but the settings shown below should
give optimal settings for most purposes.

Point-to-Point / Working Reflector
Connection
28.8k modem connection
Quality 50 - 60 50 - 60
Smeared I Frame Rate 0 255
Gamma Correction Factor 33 33
Apply Noise Reduction Filter ON ON
Lossless Luminance ON ON
Lossless Chrominance OFF OFF
ME Search Radius 0 0

ISDN (128kb) connection
Quality 60 - 70 60 - 70
Smeared I Frame Rate 255 128
Gamma Correction Factor 33 33
Apply Noise Reduction Filter OFF OFF
Lossless Luminance ON ON
Lossless Chrominance OFF OFF
ME Search Radius 0 0

LAN connection
Quality 60 - 80 60 - 80
Smeared I Frame Rate 128 128
Gamma Correction Factor 33 33
Apply Noise Reduction Filter OFF OFF
Lossless Luminance ON ON
Lossless Chrominance ON ON
ME Search Radius 0 0

Adjusting these above settings can have a dramatic affect on performance.
If you wish to experiment, here is some guidance:

* Reducing the quality setting increases the speed, and vice versa. Lower
quality settings should generally be used on slower network connections.
* Motion estimation is a very CPU intensive process. Setting the ME search
radius to "0", turns off motion estimation. This increases performance,
but at the expense of more bandwidth being used. For a "moving head" type
of picture, turning on motion estimation is not necessary, but if the
subject in the local video window moves a lot, turning up the motion
estimation may give better results.
* Switching to gray scale, as opposed to color, bypasses all the color
processing, and gives additional performance.
* Checking the option for the "Noise Reduction Filter" activates a software
noise filter that attempts to remove most of the camera / capture board
"noise". This gives additional compression, but at the expense of
performance.
* Avoid the "lossless" options in the settings, to get the best
performance. Each of these options can easily quadruple the bandwidth
requirements to keep a given speed.
* Set your communications parameters to coincide with the amount of
available bandwidth. For example, on a 28.8kbit/s modem connection, you
may want to allocate a maximum of 12kbit/s for transmission, and 12kbit/s
for reception. On a point to point LAN connection, for maximum
performance, you can easily set your transmit and receive speeds to several
hundred kbit/s.

Systems issues

The following factors have the most effect on performance, and should be
taken into consideration:

* Camera: The performance of the video codec is affected by the
performance of the camera. Cameras which generate "noise" in the signal,
make it difficult to generate high performance, as it is not possible to
compress a noisy signal as much as a clean one. The two main factors which
contribute to the noise level generated by a camera are the optics and
fluctuations due to any "auto white balance" feature. Cameras with high
quality optics (such as most camcorders) and cameras with manual override
of the auto white balance will give better performance.
* Capture boards: If you are using a video capture board in your computer,
then the faster the capture rate, and the higher the capture resolution,
then the better the overall performance. 30 fps capture boards, with a
minimum resolution of 320 x 240 with "truecolor" or "millions of color"
image depth are recommended.
* Video cards: The most important part for video playback is the rate of
pixel painting on the screen. For example, to play back a video image at
full VGA resolution at 30 fps, you need a throughput of 10M pixels /
second. True color capabilities and a minimum screen resolution of 800 x
600 makes the video look better and display faster.
* Microphones: Use a good quality microphone, that generates good audio
levels. Even inexpensive microphones often have built-in amplification, and
these give good results.
* Network connection: In general, the faster the better.

Sound

The performance and quality of sound can be controlled by the following:

* Use an audio codec setting, appropriate to the bandwidth available. For
example, there is no point in using the Intel DVI 32kbit/s audio codec on a
28.8kbit/s modem connection. Not only will you not get audio, you will
have left no bandwidth for video.
* On a 28.8kbit/s modem connection, use either the DigiTalk 8.5kbit/s or
the Voxware 2.4kbit/s audio codecs. The Voxware codec is primarily
intended for speech, but the DigiTalk codec gives acceptable quality for
music as well as speech.
* Both the Digitalk and Voxware codecs offer two settings, standard and
high. The high setting is best used on a "lossy" connection, such as the
Internet. This setting introduces a level of redundancy in the audio that
is sent, to allow the receiving PC to more accurately reconstruct the sound
pattern sent.

M