To capture 640x480 @ 60Hz, you'll need about 20Msps (million samples per second)
to capture the signal.  TI and others make video A/D converters that go into
this range.  Resolutions or refresh rates higher than this make a/d conversion a
bear, though you can get 8-bit video a/d converters that go up to and past
80Msps.  Some LCD displays use this to convert the analog signal back into
digital for the LCD controller...  Very inefficient way of doing things, but
that's what you pay for backwards compatability.  Most newer video cards now
support the digital signals for LCDs to eliminate that double conversion...  It
would be easier to get the display signal off of one of these, rather than
dealing with a/d.

Is there a reason you need to use the video signals?  It may be easier and less
expensive to get the data from the VGA card, or monitor the ISA/PCI bus for vga
write signals.

-Adam

Glenn West wrote:
>
> I'm looking at a application where I can
> capture VGA output in hardware.
> Need A/D converter tripple that will grab
> the signal. Anyone got any idea?