Re: (no subject)

John Osborne (josborne@magna.com.au)
Mon, 12 Feb 1996 07:43:00 +1000


Dave....
You'll be glad you checked :-)

The QuikCam is a *digital* camera, not an analogue one like you typical
hand-help camcorder. Consequently, it can feed digital data directly
into your parallel port where the CUSEEME software can pick it up.

What a lot of people don't realise is that parallel ports aren't just
for printers, and they are bi-directional, i.e., they can take data
*input*, not just output. Furthermore, as the name parallel implies,
all databits arrive in parallel, as apoopsed to your serial port where a
data byte must be decomposed into a serial stream of bits to be sent
out, or a stream of databits reassembled into a complete data byte
before being delivered to an application.

On a parallel port, all the data bits comprising the data byte are sent
on their own individual "pins" so no assembly/disassembly is required.
Databits can appear on the pins slightly "before" or "after" each other
(a function of cable length and other factors). This is called "skew".
Longer cables increase skew. This is why parallel cables are typically
no more than 2 metres long, where as a serial connection can go for
kilometres.

To compensate for this, one of the parallel pins is called the STROBE
line. It signals when all the data bits have arrived. The maximum
strobe rate determines the aggregate send/receive rate of your parallel
port. In a perfect world the aggregate data rate would be around 13
megabytes/second, if your PC could keep up with it.

Sorry to waffle on for so long.

Regards, John

Dave wrote:
>
> I'm sure that this is correct, but let me check.... If I purchase a
> connectrix camera (the little round one), I STILL need some kind of
> videodigitizing hardware (videospigot, a-v mac,etc) in order to use
> CU-SEE ME.
> Thak you
> Dave