[mythtv-users] XBox TVOut Quality

Derek Watson magic_cure at hotmail.com
Tue Dec 16 20:52:53 EST 2003


It's pretty simple to change the overscan using xbv. Try this...

xbv -auto XRES YRES HOC VOC

Where HOC and VOC are horizonatal overscan correction, and vertical overscan 
correction respectively. Larger numbers are more tightly underscanned.

I use "xbv -auto 800 600 4 4" to get the perfect underscan, but you'll have 
to experiment for your TV.

The only problem with this approach is that the frame rate drops to about 
15fps after running xbv. I've also tried using nvtv instead, with the same 
result.

Others are obviously having the same problem, but no one seems to know what 
the solution is. It's only apparent when running mythtv (mplayer runs at 
full frame rate), so I suspect a component that mythtv relies upon for 
rendering that mplayer doesn't use. Can anyone suggest a starting point to 
look at? Could it be related to the vblank interval getting screwed up?

I've had a dig around in the xbox nv driver source code for the 
initialisation routines, and it's using the framebuffer to set up the 
screen. So it's obviously possible to request a resolution + other bits from 
the fb driver without killing the registers since it's done when X starts.

I'm still investigating the possibility of hacking either the fb driver, 
since I see in the initialisation routines used there that the overscan 
correction is hardcoded.

Does anyone have overscan on the xbox working, or know anyone that has it 
working?

Derek.

>From: Bruce <mythtv at bruce.homelinux.com>
>Reply-To: Discussion about mythtv <mythtv-users at mythtv.org>
>To: Discussion about mythtv <mythtv-users at mythtv.org>
>Subject: Re: [mythtv-users] XBox TVOut Quality
>Date: Mon, 15 Dec 2003 23:49:55 -0500
>
>How does one adjust the xbv?
>
>Thanks,
>
>Bruce
>
>Wayne Hogue wrote:
>
> > >On Mon, Dec 15, 2003 at 09:29:07AM -0800, wishbone at h4b.org wrote:
> > > > Hmmm if you're picky then it will most likely drive you crazy.. =)  
>It's
> > >not a
> > > > myth issue though, it's a XFree86/xbox issue.  I think there are 
>some
> > >solutions
> > > > out there, but it hasn't bothered me enough to really put effort 
>into
> > >fixing
> > > > it.  Check out the usual xbox linux sites for info on that..
> > >
> > >OK, will do.  So far, I see a mention of "nvtv" use.  I will further
> > >investigate.  In the meantime, can someone in MythLand assure me that
> > >it's possible to get OverScan working (i.e., Has anyone gotten it to
> > >work for them)?  If it _is_ possible, then I am fairly confident I will
> > >be able to get it going.  Thanks!
> >
> > It is the xbox video that needs adjusting.  Need to use xbv and adjust 
>the
> > overscan for your TV.  On my box a value of 9 completely fills the 
>screen.
> >
> > As for the DVD add on.  Its the remote.  Under linux you can play DVDs 
>w/o
> > it.  But it works so well with Myth, you will certainly want to get one.
> >
> > FYI, you can get a refurbed unit from EBay for $118.99 the guy has a few 
>100
> > of em and its a buy now option.  You can also get the remote for about 
>$10
> > from ebay.  they retail for $30.  So thats abother good deal.   All in 
>all,
> > for $150 (with the shipping) you can has an excelent Media Player that
> > supports MythTV and looks good sitting with the other AV equipment.
> >
> > -Wayne
> >
> > _________________________________________________________________
> > Don’t worry if your Inbox will max out while you are enjoying the 
>holidays.
> > Get MSN Extra Storage!  http://join.msn.com/?PAGE=features/es
> >
> >   
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