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

[Doug Larrick]

On 02/02/04 16:01:01, Chris Pinkham wrote:
> How about these formulas (yDPMM unused but given for reference)::
> 
> First example shown with a 1600x900 screen that's 320x180mm w/ square
> pixels.
> 
> 	float xDPMM = pixels_wide / x_mm;          1600 / 320 = 5.0
> 	float yDPMM = pixels_high / y_mm;          900  / 180 = 5.0
> 
> 	float x_mm_needed = y_mm * XJ_aspect;      180 * 4/3  = 240
> 	int   x_pix_needed = x_mm_needed * xDPMM;  240 * 5    = 1200
> 
> 	1200/900  = 4/3 aspect ratio
> 	1200/1600 = 3/4 width of 16:9 screen.
> 
> 	dispxoff += (diswpoff - x_pix_needed) / 2; (1600 - 1200) / 2 =
> 200;
> 	diswpoff =  x_pix_needed;                  1200              =
> 1200;
> 
> This equates with the current method of using 3/4 of the 16x9  
> screen's
> width.
> 
> Now testing 1024x1024 non-square pixels w/ 320x180mm physical size.
> 
> 	xDPMM = 1024 / 320 = 3.2000
> 	yDPMM = 1024 / 180 = 5.6888
> 
> 	x_mm_needed  = 180 * 4/3 = 239.999 (say 240)
> 	x_pix_needed = 240 * 3.2 = 768
> 
> 	768 / 1024 = 3/4 width of 16:9 screen.
> 
> 	dispxoff += (1024 - 768) / 2 = 128;
> 	dispwoff = 768;
> 
> Now for my 1280x800 screen which is 332x208mm physical size (99%
> square pixel)
> 
> 	xDPMM = 1280 / 332 = 3.8554
> 	yDPMM = 800  / 208 = 3.84615
> 
> 	x_mm_needed  = 208 * 4/3    = 277.3326
> 	x_pix_needed = 277.3326 * 3.8854 = 1077.548
> 
> 	1078 / 800  = ~4/3
>     1078 / 1280 = ~85% of 1280x800 screen (which is accurate since
> it's not
> 	                                       16:9, but more like
> 14.5:9)
> 
> 	dispxoff = (1280 - 1078) / 2 = 101
> 	dispwoff = 1078;

This looks right to me.

-Doug
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
Url : http://mythtv.org/pipermail/mythtv-dev/attachments/20040202/ff838884/attachment.pgp