[mythtv-users] Myth scaling/deinterlacing vs Faroudja

[Robert Johnston]

On 6/24/06, John P Poet <jppoet at gmail.com> wrote:
> If the video on the hard drive is in an interlaced format, it would be
> nice if it could be "fed" to the video card in that same format, and
> passed onto the TV in that same format.  Unfortunately, I don't
> believe you can "feed" most video cards with interlaced data and have
> it pass it onto the TV.  If I am wrong, then please give me an
> example.

The only cards that I know of that handle this correctly are Matrox
ones. And as high-end Matrox cards are primarily used for Video
Titling, Genlocking and Chroma-Keying, it makes sense that they'd take
their "Proper" TV encoder and put it on all their cards.

But, as NVidia cards support outputting interlaced signals, you can
"Cheat" them, using some form of sync (OpenGL VSync usually) to time
your overlay refreshes to each "field" of the interlaced signal.

The only thing you have to be certain of is that you stay up-to-date
with the refreshes, otherwise (if you miss a vsync) you will end up
with double the jitter (As odd frames are being displayed on even
refreshes, and vice-versa). Fortunately, you can use
double(/triple/quadruple/quintuple/...) buffering to eliminate this
problem.

And I believe this is what Myth does (Or at least tries to, from my
experiences using an NVidia card, Interlaced SD video mode, and OpenGL
VSync).
-- 
Robert "Anaerin" Johnston