[mythtv-users] Output to HDTV

Peter Lee petel at cs.cmu.edu
Sat Jan 3 15:33:24 EST 2004

Hi, Shane.

This is possibly unrelated, but:  Are you sure this is a (de)interlacing
problem?  I am also running with a GF4MX (440) on an nForce2 board.  What I
find is that if I have twinview enabled then I get pretty annoying tearing
of the image (especially during fast panning).  As far as I can tell (from
googling around), my video card is not able to do vsync properly when
twinview is enabled.  This affects any video application (mplayer, xine,
etc), even if the application's vsync and double-buffering options are

As a result, like Jarod, I now use only the vga output from my mythtv box.
My plasma monitor has a vga input, so no component video adapter is needed.
The picture is rock-solid.  (Dvds are really beautiful.)  The only downside
of this arrangement, for me, is that the vga mode doesn't provide a
"justification" mode that stretches out the outer left/right edges of 4:3
images (but keeping the middle 50% unaffected) to fill a 16:9 display.  I
much prefer this to simply stretching the entire 4:3 image (and I also don't
care for left-right letterboxing).  Unfortunately, only the svideo and
component video modes support justification.  So, maybe I'll end up going
with Jarod's solution of a component video adapter, after all.

Or maybe I should just get a better video card.  ;-)

Or a separate front-end for each input on my plasma monitor.  ;-O


On Sat, 03 Jan 2004, Shane Warren wrote:
> Jarod C. Wilson wrote:
>> Both DVD and TV look quite good on my system. I'm feeding a 960x540p
>> signal through an Audio Authority 9A60 VGA to Component Video adapter.
>> Perhaps it is something related to your video card. I'm using a GF4MX
>> (nForce2 onboard video, actually). What are you using?
> Actually I'm using an onboard GF4MX on a nForce2 board too.  I was also
> using a 9A60 adapter to get 480p on another TV and it was having similar
> issues, plus that TV had serious overscan problems so much that it
> prompted me to finally buy a new TV.   I wasn't actually all that
> surprised when the new TV showed interlacing effects, it seems like if
> you play back an interlaced stream onto a  progressive scan output you
> will always see the effect unless you take it out w/ either a) software,
> or b) your TV takes it out.
> My TV will de-interlace video but only on the non progressive scan
> inputs (svideo,composite, and one 480i component input).  I'm totally
> surprised you don't see it, I would think this would always be an issue
> unless the source stream wasn't interlaced or the output device was
> de-interlacing it for you.
> Is there a possibility your TV/monitor/projector is doing the
> de-interlacing for you (seems unlikely since you mentioned running in
> 540p mode, which is somewhat equivalent to 1080i right, hmm actually
> maybe thats why maybe your TV always de-interlaces 1080i signals which
> it thinks your signal is, just a thought).  What is the native
> resolution of your output device?
> On my set (DLP rear projection) the native resolution is 1280x720p,
> everything else gets scaled to that.  I guess I could try outputting at
> 540p and see if my TV de-interlaces that since its native output is
> 720p, but I think I would loose some picture quality in the translation too.

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