[mythtv-users] How I got great quality TV-out on my nVidia MX4000

[Cory Papenfuss]

> I meant to ask.  The picture looks properly overscanned?  i.e. you are
> not seeing all 7??x48? (forget what res you said you have your modeline
> at) pixels right?  Just the ones that would normally show up on a real
> broadcast -- missing that certain percentage of those around the border.
>
 	If by "properly overscanned" you mean not seeing all 720x480, then 
yes, it is.  It's actually pretty easy to change the horizontal 
overscanning by just padding the sides with black, but keeping the active 
video the same.  It's a pretty easy modeline mod.  Changing the vertical 
overscanning is a different story, since you're stuck with the 525 lines 
for NTSC.  If you want it underscanned vertically, you'd need to reduce 
the number of active picture scanlines down from 480.  That's what all the 
tvout over/underscanning adjustments are doing... they just don't tell 
you that in so many words, and do some scaling in the scanline conversion. 
Bottom line is, the TV only shows Y lines vertically, and Y < 480 for 
normal TVs with overscanning.  Since horizontally is defined in analog, 
you can fill in the time for a sing sweep with as many dots as you like... 
so long as it takes 1/15734ths of a second to do each one.

-Cory


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* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *
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