video capture methods

["Dan Hoehnen" <dhoehnen@xxxxxxx>]

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Hi everyone,

I know this topic has been covered before, but I never had a need and so
never really payed close attention.

I need to be able to capture an image from a camera.  The solution should
be
generic in that it uses a video capture card and thus can use any camera. 
I
really don't want to have to buy a QuickCam or other similar camera.  I
want
to be able to add this capability to an existing house that already has
cameras installed.  But, I would still like to hear about any neat
solutions
you have, no matter what type of camera and other hardware is used.

My need is really to be able to capture images when motion is detected in
the driveway or at the front door.  So ideally, I should be able to capture
an image from any camera based on which motion detector saw motion.

It seems that some kind of a capture card with a tuner on it should be able
to be made to  change to the desired channel and capture the image.

Example setup that I think should work:
1) modulate all cameras onto their own channels.
2) feed this signal to video capture card.
3) when motion detected, change capture card tuner to desired channel and
capture.

The 3 challenges I can see right away are 1) how to change the capture
card's channel and 2) how to make sure the saved file gets a new name each
time, or somehow does not overwrite the previous file in case I have not
gotten it yet, and 3) how to tell the card to capture.

I guess I can send keystrokes to the capture card's software to change a
channel and to start the capture.  But, is this reliable?  There is also
software that detects motion from the camera's image changing, maybe this
is
the way to go?  I'd really prefer the first option as it would allow me to
capture an image whenever *I* wanted to, not whenever the *SOFTWARE* wanted
to.

Ideas?

Thanks,
Dan