Why EDID is not trustworthy for DPI

Matthew Garrett mjg59 at srcf.ucam.org
Thu Oct 6 15:46:26 UTC 2011


On Thu, Oct 06, 2011 at 11:39:16AM -0400, Jon Masters wrote:
> On Thu, 2011-10-06 at 16:20 +0100, Matthew Garrett wrote:
> > On Thu, Oct 06, 2011 at 11:14:56AM -0400, Jon Masters wrote:
> > 
> > > How about "EDID as it exists today". Since you're able to so beautifully
> > > explain what the pitfalls are, I'd assume you've raised this with the
> > > VESA and asked that they revisit this in the future to accurately
> > > provide DPI information that Operating Systems can rely on?
> > 
> > The specification provides everything needed to express this data 
> > accurately, and proves the worth of specifications by virtue of 
> > approximately nobody actually implementing it correctly.
> 
> How about an actual DPI value?

The DPI depends on the mode. Not all the world is an LCD, and even there 
it depends on whether you're native, scaling or scaling with constrained 
aspect ratio.

-- 
Matthew Garrett | mjg59 at srcf.ucam.org


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