Video Capture from the screen - possible?

Steve Loboyko (slob@MINDSPRING.COM)
Wed, 18 Jan 1995 23:21:53 -0500


It has been suggested to capture video from a program displaying video to
yield better hardware-independence for Cu-SeeMe.

Well, it would be nice, but I don't think it would be feasible, I considered
writing my own teleconferencing program for Windows using this principle,
but, in a strange turn of events, I thought before coding...

It would be just too darned slow. Assuming your bitmap on the screen were a
true bitmap and not a "hole" in your window (like those boards that use the
"feature connector" make, the data flow would be:

driver (wfw or some other program) > display program (i.e., like the one
with VfW, PC memory >Video RAM>
PC memory > compression >tcpip

Instead of Cu-SeeMe's (i think)

VfW driver >PC memory >compression >tcp/ip >video RAM (ya should get a rate
like what you put out)

Video memory is already hurt by wait states on all but the hottest boards,
and no bargain even on my 1024/768/256 BitBlt in hardware VLB board.

Also, you would be at the mercy of the display program for yields.

I think that a Mac based program would have similar constraints.

However, I think that there is room for another videoconferencing program
that would be more like slow scan TV for those of us (like me), with a
dial-up connection, that would place a high priority on audio and a low
priority on video, yielding maybe a frame every three seconds. Such a
program _could_ be a lot more independent of hardware...and less than a
propeller head / rocket scientist (i.e., me) could write it...

PS: the capture a window feature would be very useful for showing a distant
party somthing on your screen, though, kind of like what the high-end
videoconferencing systems have...

Remember that scene in Star Trek, where the "bad captain" says, "if I am
wrong, may the gods strike me dead now???" Well, if I am...
Steve Loboyko
Software Engineer
cR Solutions, Incorporated
11285 Elkins Rd suite G-1
Roswell GA 30076

slob@mindspring.com
hhtp://www.mindspring.com/~slob/home.html

________________________________________

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