[mythtv-users] Vertical scaling in HD shows

Michael T. Dean mtdean at thirdcontact.com
Tue Apr 1 00:25:49 UTC 2008

On 03/31/2008 07:44 AM, Doug Larrick wrote:
> DaveD wrote:
>>   dimensions:    1920x1200 pixels (524x321 millimeters)
> I think this is your problem.  MythTV computes the screen aspect ratio
> from the display size (524x321 mm).  In your case this is somewhere
> between 16:9 (which would be ~524x295 mm) and 16:10 (which would be
> ~524x328 mm)  It is probably snapping the display's aspect ratio to 16:9
> instead of 16:10.  Inserting a "DisplaySize" directive in your xorg.conf
> in the appropriate location (Google is your friend) should fix it up.


And, if you (or anyone else) would like to do a good deed for the
community, you could update those pages and:


for 0.21 to get rid of all mention of the requirement for 100x100DPI and
instead specify that the only requirement is that the display be
configured with the appropriate aspect ratio as determined by the
physical measurement of the screen.  Therefore, the DisplaySize or DPI
can be adjusted as desired so that fonts appear at a size that's
readable.  (I.e. though many would claim my using 100x100DPI on my 67"
HDTV, which actually has a 33x33DPI, is wrong, I would argue that anyone
who configures X to use 33x33DPI is wrong as an 8pt font would be only
3.67pixels high, 10pt is 4.583, 12pt is 5.5, etc.--all of which are
unreadable, and since many apps use these font sizes by default...)

For the DisplaySize, it's as simple as choosing any 2 values that are
multiples of the aspect ratio (i.e. for 16:9, you could use "16 9", "32
18", "128 72", "160 90", "320 180", "480 270", or whatever--even, to get
good font sizes, using the values in the table of DisplaySizes that give
100x100DPI with square pixels).

For the DPI setting that NVIDIA allows, it's more difficult as the user
would have to do the math to determine what values to use.  Therefore,
it's more appropriate to use DisplaySize (which means that DPI must
/not/ be specified) for 0.21 and above.  However, you can mention that
for a display with square pixels (i.e. whose pixel aspect ratio equals
the screen's physical aspect ratio), simply choosing the same DPI value
for X and Y will work--e.g. 100x100DPI, 80x80DPI, 133x133DPI, or whatever.

You may want to explicitly mention that choosing to use a DisplaySize
that results in a DPI near 100 will likely make fonts in all apps (even
xterms, etc.) readable even with the 10-foot user interface.


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