[mythtv-users] OT - aspect ratio and non-square pixel display

[Michael T. Dean]

On 05/20/2013 05:12 AM, Jeremy Jones wrote:
> On May 19, 2013 10:29 PM, "Michael T. Dean" wrote:
>> On 05/19/2013 10:45 PM, Jeremy Jones wrote:
>>> Hi,
>>>
>>> I have an older wide screen (16:9) plasma with a native resolution of
>>> 1024x768.  It will accept a resolution of 1280x720, but it overscans.  In
>>> the past I just used a setting in the nvidia driver to compensate for the
>>> overscan. At some point that feature of the driver went away. My system
>>> defaulted to the native resolution of 1024x768 and myth has been treating
>>> the display as a 4x3 screen.  I set out to fix this this weekend and found
>>> a page on the MythTV wiki that explained how to set the aspect ratio using
>>> displaysize in the coefficient.conf file.  Trouble is adding that line has
>>> no effect.  It seem that the setting is controlled somewhere else.  I'm
>>> running mythbuntu 12.04.
>>> Anyone know what could be overriding that setting?
>>>
>> coefficient.conf?
> Xorg.conf
> I should really proofread better when using my phone for typing email.
>
>> You need to either set the DisplaySize in X or set the resolution and DPI
>> and let X calculate the display size, so it can calculate the physical
>> aspect ratio.
>>
>>
>> http://www.mythtv.org/wiki/Display_Size
>> http://www.mythtv.org/wiki/Specifying_DPI_for_NVIDIA_Cards
> Yep. That's the page I followed.
>
> The displaysize line in X had no effect. I think something else is
> overriding it, but I can't figure out what.
>

Yes, most distros--in their quest to "help" you by making X 
config-file-less so you don't have to write a config file--do fun things 
like hard-code a -dpi setting on the command line used to start X, which 
tells the server to completely ignore any configuration-file specified 
DisplaySize values and even driver-specific configuration-file values 
such as DPI (and also makes the DPI meaningless).  And, to make matters 
even more fun, different distros have different ways of starting X, so 
finding that -dpi can be a challenge (some may put it into the startx 
script, others call startx -- -dpi 100 or similar from some other script 
and others use other mechanisms).

It's possible something like this is overriding your configuration.

Mike