How to set underscan factor

[Alex Deucher]

On Fri, Jan 21, 2011 at 9:02 AM, Daniel Klaffenbach
<danielklaffenbach at gmail.com> wrote:
> Hi,
>
> I have connected my TV via HDMI to my Radeon HD 3870. I am running the latest
> git versions of Linux 2.6 (with KMS), mesa, libdrm and xf86-video-ati.
>
> Right now the image is either too small for the TV (black area around the
> image, underscan=on), or the image is too large for the TV (window decoration
> etc. missing, underscan=off).
>
> For the reference, this is what I am talking about:
>
> Image with underscan off: http://goo.gl/o8lP4
> Image with underscan on: http://goo.gl/BuBVO
>
> I experimented with the "underscan" parameter using xrandr, but there only
> seems to be "on" and "off". Is there any way to scale the image so it fits to
> the screen? The AMD Catalyst Control Center has a slider for this which works
> well, but I cannot find a corresponding option (underscan/scaling factor) for
> the OSS driver.
>
> A while ago this was all working correctly (I needed to turn underscan off and
> the image would fit perfectly to the screen).


There are underscan controls that were added in 2.6.37.  Controlled
via connector properties just like underscan.  Also, check your TV and
see if it has a a setting (often called fit or 1:1, etc.) that
disables overscan.

Alex

>
>
> Regards,
> Daniel
>
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