Re: [mediaqueries] Media Source Extensions and device capabilities

On Tuesday 2014-11-18 14:59 +0100, Florian Rivoal wrote:
> > On 14 Nov 2014, at 18:13, L. David Baron <dbaron@dbaron.org> wrote:
> > Then again, I probably wouldn't be against just having a separate
> > unit for device pixels (or, for that matter, for true lengths),
> > although I'm not sure I like 'dpx' as the name (looks too much like
> > 'dpi’).
> 
> We already have dppx (Dots Per PiXels) for the resolution MQ, to query the number of physical pixels in a css pixels, so I don’t think dpx is a name I’d recommend.
> 
> As for physical units for lengths, coming from mostly anyone else, I’d probably reply with the usual story about why this is misguided, but as you know all these already, I am curious as to why you think this is a potentially good idea.

I think it's a potentially good idea here because what we're talking
about is media resource selection.

Consider the problem as follows:  the server can offer a video at
four different resolutions, ranging from, say, 320x180 up to
1280x720.  (I'm making up these details, but this is the general
idea.)  They want to offer the highest quality one that's going to
be useful, but don't want to waste bandwidth sending the high
quality one to a small display.

So the right choice of video is a function of how many *device
pixels* wide and tall the space for the video is.  It's not a
function of CSS pixels; treating it as such would send low quality
video to displays with more than one device pixel per CSS pixel.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
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