720x576Noscale does scale 720x576Over doesn't scale

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Glidos
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720x576Noscale does scale 720x576Over doesn't scale

Post by Glidos » Sat Sep 13, 2008 5:12 pm

I've recently set up a MythTV frontend using Minimyth on a board with a CN700 and a
VT1622A. I'm using TV out via S-Video to a CRT TV with Scart input. I initially set up
mode 720x576Noscale, and was pleased to find the TV image fitted to the TV screen
exactly, but there were a few strange things that started to make me think that the image
was being scaled:

1) The OSD images had to be adjusted to about 650x550, for it to also fit the
TV screen.

2) The TV image showed various artifacts that could be exaplain by scaling (jagged
diagonal edges, rippling during pans, a general softness of focus).

When I first looked at the X screen via VNC I found TV was being scaled. The X screen was
720x576, but the decoded TV image was being mapped onto a 650x550 subarea, and this area
was somehow mapping exactly onto the TV screen.

I've just swapped to using the mode 720x576Over. I get a much better quality image, and
now the TV image extends off the edge of my TV screen by the same amount as the OSD. If I
look via VNC, I can see the TV image mapping directly to the full 720x576 area of the X
screen.

Anyone know what's going on here? Also, anyone know how I should adjust the mode to fit
correctly to the TV. I have no real experience of adjusting X. Is there a tool that
allows on-the-fly adjustment of mode variables?

Cheers,
Paul.

Pablo
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Post by Pablo » Sat Sep 13, 2008 9:58 pm

Whether or not MythTV television playback uses the same size as the MythTV GUI is controlled by the MythTV setting "Use GUI size for TV playback" on the "Screen settings" screen under the "Utilities/Setup -> "Setup" -> "Appearance" menu.

The *Noscale and *Over Xorg modes control whether or not the openChrome driver scales the image.

For the best image quality, the best configuration is usually to uncheck the MythTV setting and use *Noscale mode for the Xorg mode.
MiniMyth running on an Acer ApireRevo 3610 and a Zotac ZBOX-ID80-U. Find out more at my MythTV page.

Glidos
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Posts: 164
Joined: Tue Sep 02, 2008 8:50 am

Post by Glidos » Sat Sep 13, 2008 11:44 pm

What you describe is exactly what I expected, but that's not what it does. I didn't check the MythTV setting. When I used Noscale, it did scale to exactly the subarea of the X screen that appears on the TV. When I used Over, it did not scale and the quality was good.

Glidos
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Posts: 164
Joined: Tue Sep 02, 2008 8:50 am

Post by Glidos » Sat Sep 13, 2008 11:56 pm

The problem I have now is that not all of the X screen is visible on the TV. I'm guessing I need to adjust the mode variables directly, but I'm yet to find out how to do it.

Glidos
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Post by Glidos » Sun Sep 14, 2008 8:18 pm

Sorry, I was talking rubbish: I did have "Use GUI size for TV playback" set. The theme I'm using makes it difficult to tell if an option it checked. Now I've unchecked it, I have Over and Noscale working much the same as each other.

I still have only a subarea of the X screen visible on the TV. Is there anything I can do about that?

Pablo
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Post by Pablo » Tue Sep 16, 2008 5:02 am

There are settings in the menus for adjusting the size and position of the MythTV GUI. You can find them on the same screen as the "Use GUI size for TV playback".

You might also try using the "Screen Setup Wizards", but I have never used them.
MiniMyth running on an Acer ApireRevo 3610 and a Zotac ZBOX-ID80-U. Find out more at my MythTV page.

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