Re: Once upon a time, there was a device...

["Michael J. Mahon" <mjmahon@aol.com>]

Jon wrote:
> Hehe,
> This topic seems to eternally come in and out of the group :D.  Is
> there a way do make a DIY circuit to convert the RGB to component ?  or
> maybe there's an off the shelf chip that does that already and all you
> got to do is connect the wires to it?

Yes, it seems ripe for inclusion in the FAQ, if it's not already there.

Component video is just a re-encoding of the RGB signals, complicated
slightly by the need to add composite sync to the Y signal.

All of this is pretty simple analog circuitry, involving three or four
video opamps, which are now a dime a dozen.  Many of them are rail-to-
rail, so they only need a +5v supply (present on many RGB connectors).

I published a URL for an manufacturer's appnote on this three years
ago, but it seems to have gone dead.  A URL to a .gif of a similar
circuit (for VGA in, therefore needing to create composite sync)
appeared in this forum recently.

Altogether, a triple- or quad- video opamp and a dozen resistors and
a couple of decoupling capacitors would do the job, so the cost should
be under $10.  Of course, a box, connectors, and labor could run that
up some, but the $100+ boxes being sold that do exactly the same thing
are clearly priced for the "home theater" market.

-michael

Parallel computing for 8-bit Apple II's!
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