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Re: Wide Color Gamut and High Dynamic Range displays

From: Mark Watson <watsonm@netflix.com>
Date: Wed, 28 Jan 2015 11:27:25 -0800
Message-ID: <CAEnTvdDsWdOHWKAusO_0M9mkUdHwrq1wT8Jhaw0F4sEfbkk1PA@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: "www-style@w3.org" <www-style@w3.org>
On Wed, Jan 28, 2015 at 10:32 AM, Tab Atkins Jr. <jackalmage@gmail.com>

> On Wed, Jan 28, 2015 at 9:02 AM, Mark Watson <watsonm@netflix.com> wrote:
> > All,
> >
> > It would be nice to be able to detect whether the display has the
> capability
> > of rendering Wide Color Gamut and High Dynamic Range video.
> The wide gamut, at least, is covered by the (color) MQ
> http://dev.w3.org/csswg/mediaqueries/#color

​That's the bit depth, which is important, but orthogonal to the color
gamut. Greater bit depth means you can identify colors within the supported
colorspace more accurately (less quantization). Wide Color Gamut refers to
an increase in the range of possible colors, such as with BT.2020 [1].

> I'm unsure what High Dynamic Range is, so I dunno if there's anything
> applicable in CSS so far.

​Standard video signals encode luminance within a particular range (up to
100 candelas/m^2). High Dynamic Range refers to signals encoded with a
higher luminance range. To be worth using you need the display itself to
support higher brightness levels (actually most displays go higher than 100
candelas/m^2 these days) but also for the media pipeline to support the
higher luminance range and transmission of that to the display.

In both cases, the relevant capabilities are distinct from the codec: it's
about the interpretation of the 8 or 10 bits per pixel per component that
are the output of the codec.


[1] http://en.wikipedia.org/wiki/Rec._2020​

> ~TJ
Received on Wednesday, 28 January 2015 19:27:57 UTC

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