[mythtv-users] Fix for distorted image on CRT TV

[Cool Frood]

On 8/8/06, Steve Daniels <steve.p.daniels at googlemail.com> wrote:
>
>
> > -----Original Message-----
> > From: mythtv-users-bounces at mythtv.org [mailto:mythtv-users-
> > bounces at mythtv.org] On Behalf Of Joe Votour
> > Sent: 09 August 2006 04:06
> > To: Discussion about mythtv
> > Subject: Re: [mythtv-users] Fix for distorted image on CRT TV
> >
> > > Cool Frood wrote:
> > >
> > >>Hi,
> > >>
> > >>I have a standard CRT TV (Philips 20" flat screen) which I'm using
> > >>with an NVidia FX5200 using an S-Video TV-out.  The problem that I
> > >>face is that the image on the screen is somewhat distorted, with the
> > >>top of the image being narrower than the bottom.  Also, the image is
> > >>very slightly tilted clockwise.  I also noticed that the curving of
> > >>the image at the top becomes more pronounced when the screen is
> > >>showing brighter colours?  Is this to be expected, or is there
> > >>something I can do to fix it?  It's not very annoying, but I'd really
> > >>like to get an image quality close to what I can get by directly
> > >>hooking up the cable box to the TV.
> > >>
> > >>Thanks.
> > >>
> > > I get similar effects to what you describe also using a FX5200 (replaced
> > > my 5600 with it as this particular card doesn't have a fan on it), but
> > > I'm currently only using Composite out (I keep meaning to try S-vid to
> > > see the quality difference but it means a bit of mucking around that I
> > > haven't had time to do recently).
> > > My pic on the TV , while of a fairly good quality (I've also got a
> > > PVR-350 in the box that I used to use for TV out, but I now want the
> > > accelerated OpenGL etc for goom, xmame, stepmania  etc etc), definately
> > > seems to have what you describe, the top part of the picture bends in,
> > > and there is also a very noticeable brightening/darkening of the whole
> > > display when I move the cursor/highlight bar over the various menu
> > > options -  currently using GANT theme, so I think maybe it's linked to
> > > the colours displayed with the associated icons for each option.
> > >
> >
> > Back when I was using S-Video for TV output, I would see the same problem.
> >  Now that I'm using VGA (my current TV has a native VGA connection), I
> > don't have the problem (that I've noticed).
> >
> > I noticed though that in comparing the size of the picture from the nVidia
> > and the PVR-350, that the PVR-350 actually displayed less of the picture -
> > it was overscanning (as it was intended to do).
> >
> > I would try comparing the picture that you see on the nVidia card to the
> > one that you see on the TV.  If you see more picture on the nVidia card
> > (at the edges), then increase the overscan on the nVidia card until the
> > effect goes away.
> >
> > You'll lose some of the items at the bottom of the screen in the MythTV
> > configuration menus, but they weren't really designed with the concept of
> > "hidden zones" (defined in the NTSC specification) very well.
> >
> > -- Joe
>
> Which is what the appearance settings can be used for, you can allow the
> video output to be displayed full screen as it were, and then restrict the
> control gui to top/left offsets and height and width values iirc.
>
> HTH
>
> Steve :-)
>
Somehow I couldn't figure out how to use the offset values correctly.
When I tried to change the x-offset, it make the image move up by
changing the y-offset and I gave up at that point.  Perhaps if I try
harder, I'll figure it out.

In any case, I tried hooking up my DVD player with the same S-Video
cable, and I didn't get any distortion yet.  I didn't try the test to
figure out if my regular TV signal chops off more of the image than
the TV-out does.  However, when I tried my DVD player, I managed to
get the S-Video cable more untangled from the rest of the cables, so I
seem to be getting less distortion now.  It's not perfect, but I think
I can live with it at this stage.  If I'm feeling enthusiastic, I'll
try increasing the overscan.

Thanks,

Akshat