[mythtv-users] Which Nvidia card for TV-OUT?

[Jim Paris]

> I don't suppose you're inquisitive enough to have popped the lid off one
> of these? If not would you? I believe I have the appropriate design
> together to build one and would be interested at roughly what's actually
> inside one of these. I just need to get some slightly less off the shelf
> parts (digikey/farnell/RS have them though) and layout the board.
> 
> The way I see it they are very dumb and mainly perform the colour space
> conversion and combine the sync into the Y signal. There can't be that
> much in them given their size either.

The color space conversion is non-trivial, but shouldn't be too bad
with a handful of high-speed opamps.  On the other hand, if you either
have a video card that supports sync-on-green or build a simple sync
combiner circuit, I always thought it would be devilishly clever to
just directly connect the VGA's (R,G,B) to (Pr, Y, Pb), and do the
color space conversion in software.  The signal levels are compatible.
It could be very efficient: for MPEG playback, you could just skip the
YUV->RGB conversion while decoding, and changing the OSD colors
requires no extra work.

Then I realized I could hack a VGA input into my TV, and stopped
thinking about this.  It would still be cool to see, though.

-jim