[whatwg] audio and video: volume and muted as content attributes?

[Bjartur Thorlacius]

On 5/31/10, Silvia Pfeiffer <silviapfeiffer1 at gmail.com> wrote:
> On Tue, Jun 1, 2010 at 6:48 AM, bjartur <svartman95 at gmail.com> wrote:
>>>I just came across a curious situation in the spec: IIUC, it seems the
>>>@volume and @muted attributes are only IDL attributes and not content
>>>attributes. This means that an author who is creating an audio-visual
>>>Webpage has to use JavaScript to turn down (or up) the loudness of
>>>their media elements or mute them rather than just being able to
>>>specify this through content attributes.
>>>If you want to control the volume for the user after the page loads
>>>then yes, you'll need JavaScript.
>>>I've searched the archives and didn't find a discussion or reasons for
>>>this. Apologies if this has been discussed before.
>>>
>>>I am guessing the reasons for not having them as content attributes is
>>>that anything that requires muting of audio-visual content is assumed
>>> to need JavaScript anyway.
>>
>> Exactly.
>>
>>>However, if I have multiple videos on a page, all on autoplay, it
>>>would be nice to turn off the sound of all of them without JavaScript.
>>>With all the new CSS3 functionality, I can, for example, build a
>>>spinning cube of video elements that are on autoplay or a marquee of
>>>videos on autoplay - all of which would require muting the videos to
>>>be bearable. If we added @muted to the content attributes, it would be
>>>easy to set the muted state without having to write any JavaScript.
>>
>> If you need the audio to be muted you should use CSS. If you need to
>> control volume dynamically you need scripting.
>
> I am not aware of a CSS property for media elements that lets you
> control the muted state. Can you link me to a specification?
Well, http://www.w3.org/TR/CSS2/aural.html defines volume and
play-during. Play-during can stop, autoplay and repeat sounds.
It's not obvious to me how this will apply to elements that represent
audiovisual content but volume: silent; unambiguously mutes content.
Decorating audio (such as background music in games or videos)
seem to be even more easily styled for some reason. Multiple
soundtracks can be muxed and assigned different loudness.
Also @media aural {display: none;} can be used on audio elements
but I haven't read the specs properly so I don't know if that would hide
an <video> element when inside of an @media aural clause.

CSS 3 aural is still to be done so more capabilities may be suggested.

>> Well, you have a point. That can be done by increasing the volume
>> of the soundtrack itself, metedata (like embedded volume metadata in
>> MPEG files) and should be possible in CSS. Adding it to HTML as well
>> seems redundant.
>
> Are you saying that a Web author needs to edit the media resource in
> order to change the default volume setting for the resource? I think
> that's a bit of a stretch. Also, if you have a pointer to how this can
> be done in CSS, that would be highly appreciated.
Not necessarily, just pointing out that it would be a good idea to fix the
soundtrack if it's broken. CSS is perfect for these kind of things so I
recommend extending that rather than HTML.

-- 
kv,
  - Bjartur