[mythtv-users] TV out picture is not rectangular

[Gert van der Knokke]

Hamish Moffatt wrote:

>I've got an ASUS 9180 Geforce4 MX440 card which I'm using for TV out on
>my MythTV pc. The quality is quite good however the sides of the picture
>are not straight. The top and the left are not too bad, but the right
>hand side is quite shocking. 
>  
>
I guess you are normally not seeing the problem while all broadcasts are 
overscan(d) already..

Since your VGA card is purely digital and controlled by a quarz 
triggered PLL in creating the sync and dotclock signals, I cannot 
believe the distortion is coming from the card.

My guess is your TV needs some serious re-adjustment, but to make sure: 
try displaying a test picture with a wide spaced whiteline grid, 
preferably from a TV signal/test pattern generator and see how the 
vertical lines look.
Another simple test: try measuring the black space around a full 
teletext page. (Does it look distorted too ?)

If it is a Sony and several years old: chances are the deflection yoke 
has come loose and slided backward for a  couple of millimeters. Other 
signs of this problem are reduced convergence in one corner (white lines 
look like they have a colored line next to them) Don't try to fix this 
yourself however! Chances are you'll end up with a broken neck (of the 
picture tube that is.. :-) ask a qualified repairman!
Nowadays the yokes are better fixed.

If it is a newer set: chances are it can be fixed through a special 
service menu of your TV set, ask your local repairman if it has any 
(note the brand, type and serial number and possibly a chassis number of 
the set, normally found on the back)
Sometimes you can activate it with the remote using a special code. If 
you don't know what to do with these kind of picture  geometry settings, 
than let a qualified repairman do it for you! You can seriously mess up 
a TV set by making wrong adjustments.

>When I use overscan to make the picture fill the screen, I lose quite a
>lot off the edges in the wider parts. Even as much as losing the right
>hand border in the watch recordings list, for example.
>
>  
>
You can adjust this in the settings. It will display menues and such 
with a presettable offset from left and/or right and up and/or down.

>I was hoping that xvidtune might help, but when I tried it, none of the
>adjustments seemed to have any effect. I saw the picture flicker (I
>turned on auto mode), but not actually move. Does it have any effect
>with TV out usually?
>
>  
>
Probably not since the TV-out is generated by a separate chip on most 
VGA cards. They have there own set of adjustment registers. (only 
positioning, not geometry settings)

>Finally, is there anything that can be done to improve the shape?
>Or is it likely that the TV encoder is just rubbish and I should go
>buy another card?
>  
>
Nope, see above.

>I'm using composite out, as S-video isn't too convenient (picture
>switched through the A/V receiver, etc). However I could try it
>temporarily if there's a suggestion that it might help.
>
>I've tried a couple of different resolutions now and they're much the
>same. I usually run 800x600 but just tried 720x576. I'm using PAL output
>by the way.
>
>  
>
It won't make any difference.

Good luck.

Gert