[mythtv-users] Underscan in playback and recording, driver issue?

Brian J. Murrell brian at interlinx.bc.ca
Tue Sep 26 18:53:30 UTC 2006

On Tue, 2006-26-09 at 14:26 -0400, Michael T. Dean wrote:
> On 09/26/06 12:39, R. G. Newbury wrote:
> >Michael T. Dean wrote:
> >  
> >
> >>You use either MythTV to overscan the video during playback or use the 
> >>video drivers (i.e. the NVIDIA drivers) to overscan the entire desktop 
> >>(which gets the video, the menus in MythTV, the desktop outside of 
> >>MythTV, and every other application you run).
> >>
> >I tried playing with over/underscan while running mythfrontend in a 
> >window, output on my NTSC TV. The window size can be set on a per-pixel 
> >basis, but underscan reduces the size of the picture *in that window*, 
> >ie set underscan to -10 both vertically and horizontally and you get a 
> >black border around the picture, *within the window*. The window, as 
> >usual can be moved around on the desktop, which itself is subject to 
> >losing its edges due to the TV's overscan.
> >
> >How does one control the desktop size, so that I can run mythfrontend 
> >without using a window?
> >
> Re-read the above.

Wait a sec... this "overscan" setting in Mythtv does not really control

For example, on my FX5200 with SDTV out, on both the myth menus and
recorded program playback I have a black border around the viewable
area.  This is quite distasteful as it's not a sharp square black border
but skews slightly here and there.

True overscanning would expand the picture so that that edge of
displayable area is outside of the viewable portion of the screen.

Myth cannot do this.  The driver (i.e. for the FX5200) can however with
it's overscan setting.  This is what I use to get a picture that looks
like real TV, not real TV shrunk slightly and in a "box".

The problem with this is that Myth needs an inverse to it's current
overscan feature which is a "UI underscan" so that the visible portion
of the UI fit within the viewable portion of the screen.  This is
because the UI is written to stretch out to the edges of the screen,
which might look good on a computer monitor but with a true overscanning
display device leaves the UI "cut-off", stting outside the viewable area
of the TV screen.

There are "GUI {width,height,X offset,Y offset}" settings which can deal
with this, but i think calling it something more along the lines of "UI
overscan/underscan" and changing the measure from pixels to percentage
to shrink like the overscan settings would make it more intuitive.

Then again, maybe not.  I guess my real beef is calling the "Overscan"
feature "Overscan".  It's not really -- not in the same sense that real
overscanning pushes the edge of the picture off the viewable portion of
the screen.


My other computer is your Microsoft Windows server.

Brian J. Murrell
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