[mythtv-users] Question about HDTV

Howard Cokl hojoloco at yahoo.com
Tue Mar 22 23:58:35 UTC 2005


On Tuesday 22 March 2005 06:11, Cory Papenfuss wrote:
> 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                   *
> *************************************************************************

Thanks for all the info.  Unfortunately I think I am stuck with an HDTV that 
isn't going to play nicely with my mythbox.  Using the 9A60 the picture is 
less fubar than with the VHDC300 but basically everywhere except the center 
of the screen has convergence problems.  With the VHDC300 the picture was 
offset a couple of inches to the left and any attempt to adjust to the right 
on the VHDC300 resulted in no picture.  The 9A60 doesn't have any external 
adjustments, don't know about inside, don't want to open it up cause I 
wouldn't know what I'm doing anyway.  I also tried using an MX400 last night 
hooked up to the 9A60 with the same results.  So basically I am receiving 
HDTV content and watching it on my HDTV using S-Video.  
I don't think that the 9A60 is broken but my logic coming to this conclusion 
is flawed since I am basing that on the fact that the VHDC300 worked fine 
with an RCA DTC100 and the 9A60 works better than the VHDC300 with myth.  Oh 
well, thanks for your help maybe I'll look into getting an nvidia 6200 with 
component out.

-- 
Howard Cokl
"in a world without walls and fences, 
who needs windows and gates?"



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