[mythtv-users] Question about HDTV

[Cory Papenfuss]

On Mon, 21 Mar 2005, Howard Cokl wrote:

> I had my myth box hooked up to my old Hitachi HDTV using an AA 9A60 and it
> appears that the 9A60 makes the convergence go off.  It's not a modeline
> problem because it occurs during boot up before X starts.  I was previously
> using an RCA VHDC300 for the same purpose and it did the same thing but only
> worse.  Is there any thing I can do or look at to fix this?  I am back to
> using S-Video for the time being since the picture is superior to
> vga->transcoder route.  I'm using an nvidia 5200 right now, does this sound
> like a video card problem?
> --
 	I've seen a (really) old CRT projection TV that had differing 
convergence depending on the signal that was being displayed.  Its 
internal test pattern for convergence changed whether there was a channel 
displaying or not.

 	Anyway, the convergence *shouldn't* change unless something is 
broken.  Sometimes moderately designed TV's have issues with sync 
polarity.  I'd try a modeline that changes the sync polarity in case the 
A960 does sync a little different on different polarity.  I don't recall 
if an A960 has adjustments for L/R, but you might want to try that.  It's 
also slightly possible the A960 is broken and has different length in the 
signal path.  You *are* using the same length cables for each of the Y, 
Pb, and Pr, right?  If you're running a 30MHz dotclock down a 2m cable, 
there are 1/3 of a dot to be drawn on the screen *IN TRANSIT* on the 
wire.  Doesn't sound like much, but it's just something that a lot of 
people don't think about.  Longer cables/high dotclocks make it worse.

-Cory

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