[mythtv] [PATCH] Potential display aspect ratio patch for non-4:3

[Chris Pinkham]

> >I have a 1280x800 resolution laptop and noticed that the code was assuming
> >my display is 16:9 since it's not 4:3.  This causes the 4:3 aspect video to
> >have black bars added that are too large so the video is displayed at almost
> >a 4:4 ratio instead of the desired 4:3 ratio.  Instead of assuming the
> >display is 16:9 if it's not 4:3, the attached code will calculate the
> >desired video width based upon the video ratio and the display height.
> 
> Remember that you can also set "DisplaySize" in your xf86config file in 
> order to tell it what the REAL aspect ratio is of your screen.  For 
> example I can only get my tvout to work in 720x576 instead of 768x576 
> and so I set the DisplaySize variable and now mplayer, myth, etc all get 
> the video display aspect just perfect.

The width and height in MM that Myth is getting are correct though.  Why would
I want to fudge the numbers in my XF86Config file to fix Myth?  My screen
actually is a 1280:800 (ie, 1.6:1) ratio screen.  It is a widescreen laptop
by Dell (although you could also think of it as a 1280x1024 screen with
the bottom 2 inches chopped off). :)  The code currently assumes
anything that's not 4:3 is 16:9.  When I display full-screen on the 1280x800
display, a 4:3 image should be displayed at 1066x800 pixels (4:3).  The
current code puts in black bars on each side that are ~200 pixels wide which
makes the actuall image displayed 880x800 which is almost a square.  My
calculation would put in black bars which are ~107 pixels wide giving a
display area of 1066x800 which is 4:3.  On a 16:9 ratio screen (for example
1600x900) it would still give the correct size black bars as well (in this
instance 200 pixels wide each).

formula is:

dispxoff += (dispwoff - (disphoff * XJ_aspect)) / 2;
(1600 - (900 * 4/3)) / 2 = 200 (16:9 actual screen has 200 pixel borders)
(1280 - (800 * 4/3)) / 2 = 107 (1280x800 screen has 106 pixel borders)
(640 - (480 * 4/3)) / 2   = 0   (640x480 screen has 0 borders

It seems like the replacement calculation I made in the code will work no
matter what the aspect ratio is because it calculates rather than assuming
16:9, but I'd like to for someone with a 16:9 screen to test (or anyone
with non-16:9 screens as well).

-- 

Chris