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Re: [mediaqueries4] Media queries for multichannel audio ?

From: Mark Watson <watsonm@netflix.com>
Date: Thu, 21 Mar 2013 00:26:18 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>
CC: Sylvain Galineau <galineau@adobe.com>, Kenneth Rohde Christiansen <kenneth.r.christiansen@intel.com>, "florian@rivoal.net" <florian@rivoal.net>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <78181253-FF4C-4E6D-88CE-CA189D42A625@netflix.com>

On Mar 20, 2013, at 4:56 PM, Tab Atkins Jr. wrote:

> On Wed, Mar 20, 2013 at 4:49 PM, Sylvain Galineau <galineau@adobe.com> wrote:
>>> Tab suggests we need some way to declare the resolution, or channel
>>> count, of the media to the UA, but that would move the responsibility for
>>> deciding how to match media properties with physical properties from the
>>> user to the UA: a different distribution of responsibility from selection
>>> based on media queries. Why should these particular properties (physical
>>> resolution, audio output channels) be treated differently from others
>>> (color depth, aspect ratio, etc.) ?
>> 
>> Sorry, I don't follow the distribution of responsibility argument at all.
>> I - and, I think, Tab - is suggesting media queries pick the right source
>> so you then know what stream you need.
> 
> I've commented on both sides of this - I don't particularly care
> whether it's done by a MQ selecting the number of output channels, or
> a declaration of the number of output channels that your source has.
> The two are functionally equivalent, though one or the other may be
> more convenient.

They're not really functionally equivalent at all.

In one approach the script says "use this media in these conditions", where the conditions are constraints on properties of the output device, expressed as a media query. The UA chooses the first media for which the constraints hold based on the properties of the output device.

In the other approach, the script says "this media has the following properties", and it is up to the UA to decide how properties of the media should be matched with properties of the output device.

Now, if there is only one sensible mapping between media properties and device properties, and if all UAs implement this same sensible mapping, then perhaps there is no difference. But those a two big "if"s. At least one example where there is ambiguity is if the physical resolution of the display is in-between that of two of the possible media streams: should the UA downsample the high-res content or upsample the low-res one ? An author-provided media query would tell it what to do.

Further, since the approach to date with media queries has been the first one, what would be the rationale for using the second approach for these specific properties (audio channels, physical resolution, supported frame rates) ?

ůMark

> 
> ~TJ
> 
Received on Thursday, 21 March 2013 00:26:47 GMT

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