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Re: [mediaqueries4] Media queries for multichannel audio ?

From: Mark Watson <watsonm@netflix.com>
Date: Wed, 20 Mar 2013 17:17:44 +0000
To: Kenneth Rohde Christiansen <kenneth.r.christiansen@intel.com>
CC: "florian@rivoal.net" <florian@rivoal.net>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <161F8D45-D7EC-4501-A041-22E2937C1A5A@netflix.com>

On Mar 20, 2013, at 9:44 AM, Kenneth Rohde Christiansen wrote:

> Well CSS is defined at arms length :-) but I understand the difficulty
> in defining the common viewing distance (in arms lengths) for TVs.
> 
> Do you have some optimal viewing distance given the screen size. With
> that in mind, a right upscaling (device pixel ratio or device dots per
> pixel - dppx) could be defined for TV browsers, given the screen
> resolution.

That would be needed to solve the general problem of the CSS pixel definition for TVs and therefore the physical size that things-measured-in-CSS-pixels should be rendered.

That's actually not the problem I'm trying to solve. When it comes to rendering video full-screen, you always fill the screen with the video, however near or far the user is sitting. So things appear bigger to users with bigger screens, unlike things-measured-in-CSS-pixels. And so to decide on the appropriate resolution to serve I need to query the physical resolution.

…Mark

> 
> Kenneth
> 
> On Wed, Mar 20, 2013 at 4:37 PM, Mark Watson <watsonm@netflix.com> wrote:
>> 
>> On Mar 20, 2013, at 8:09 AM, Kenneth Rohde Christiansen wrote:
>> 
>>> WebKit has devicePixelRatio so you can device the device size by using
>>> that.
>> 
>> This tells me the ratio between CSS pixels and device pixels, but this is still meaningless for TVs, since there is no definition of CSS pixels for TVs (a bit of a problem generally for web browsers on TVs, but nevertheless…).
>> 
>> What I need is just the device width and height in device pixels, to know when it is not worth delivering a high resolution version of the content. It's not such a big deal with HD, since there are a dwindling number of SD displays, but with 4K this will be an issue.
>> 
>> …Mark
>> 
>> 
>> 
>>> Something to query that should probably be standardized, but
>>> media queries are not exactly for querying exact values.
>>> 
>>> Kenneth
>>> 
>>> On Wed, Mar 20, 2013 at 4:03 PM, Mark Watson <watsonm@netflix.com> wrote:
>>>> Florian, all,
>>>> 
>>>> How do I progress this issue ? Do I need to file a bug ? (where?) Do I need to join the WG ?
>>>> 
>>>> There are also two other issues I'm interested in with respect to TVs:
>>>> - output frame rate (no point giving 60fps content to a 30fps display)
>>>> - screen dimensions in physical pixels (no point giving HD content to an SD display)
>>>> 
>>>> For the latter one, I am unsure about whether this can be derived from the existing width/height and resolution properties. Width and Height seem to be in CSS pixels which are explicitly defined with reference to "computer displays", so it is unlearn what is a CSS pixel on a TV.
>>>> 
>>>> Best regards,
>>>> 
>>>> Mark
>>>> 
>>>> On Mar 19, 2013, at 10:10 AM, Henrik Andersson wrote:
>>>> 
>>>>> Mark Watson skriver:
>>>>>> 
>>>>>> On Mar 19, 2013, at 9:42 AM, Henrik Andersson wrote:
>>>>>> 
>>>>>>> Mark Watson skriver:
>>>>>>>> Hi everyone,
>>>>>>>> 
>>>>>>>> Has there been any dissuasion of media queries for audio media ?
>>>>>>>> 
>>>>>>>> Specifically, I am interested in discovering whether the attached audio device supports multi-channel audio (5.1, 7.1 etc.) so that I can choose an appropriate resource.
>>>>>>>> 
>>>>>>>> I believe it would be sufficient to have a 'channel count' property which is just an integer count of the number of audio channels supported by the output device.
>>>>>>>> 
>>>>>>>> Thanks!
>>>>>>>> 
>>>>>>>> Mark Watson
>>>>>>>> 
>>>>>>>> 
>>>>>>> 
>>>>>>> I'd like to add that it could be useful to know if there is a limit to
>>>>>>> the number of mixer channels available. Some platforms use hardware
>>>>>>> mixers that have a limited amount of channels.
>>>>>> 
>>>>>> Actually, I am interested in the number of physical speakers - or more specifically the number of channels actually output from the device.
>>>>>> 
>>>>>> I have a multichannel stream and a professionally downmixed stereo stream and if there are only two output channels I'd rather provide the stereo stream than have the device do its own downmixing.
>>>>>> 
>>>>>> I distinguish between the number of physical speakers and the number of output channels because there are setups where the audio output is making proper use of the 6 output channels but has less than 6 speakers (for example soundbars, where there is audio processing which tries to simulate the effect of surround speakers using phase manipulations etc.). I consider those setups as having 6 output channels. But if the device is doing straight downmixing to stereo, I'd rather provide the professional stereo stream (which is also less bandwidth).
>>>>>> 
>>>>> 
>>>>> To clarify, I am not saying that your case is the same as mine. I just
>>>>> wanted to add a related thing that could be useful to detect. Some
>>>>> devices simply have limits on the number of sounds they can play at the
>>>>> same time.
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> 
>>> 
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>> 
>> 
> 
> 
> 
> -- 
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> Intel Denmark Aps
> Langelinie Alle 35, DK-2100 Copenhagen
> CVR No. 76716919
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> This e-mail and any attachments may contain confidential material for
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Received on Wednesday, 20 March 2013 17:18:16 GMT

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