[whatwg] Type strings to specify number of AAC audio channels

[Ian Hickson]

On Mon, 23 Sep 2013, Bolin Hsu wrote:
>
> Since the royalty for decoding surround sound AAC is higher than stereo 
> AAC, some platforms can decode stereo AAC but not surround sound AAC. 
> But the type string passed to HTMLMediaElement.canPlayType(type) doesn't 
> specify number of channels. I discussed this with some colleagues before 
> I found this list. Has this been covered by standard? Below are some 
> ideas came up during discussion:
> 
> - Use a new codec string, such as 
> HTMLMediaElement.canPlayType('audio/mp4; codecs="aac51"')
> 
> - Add a new parameter, such as
> HTMLMediaElement.canPlayType('audio/mp4; codecs="mp4a.40.2", channels="6")

These seem like appropriate approaches. They would merely need updates to 
the relevant RFCs.


> - Add new element for platform configuration. Some platforms can only
> output stereo audio, so the surround sound is down mixed to stereo. This
> can potentially query the platform if it can really output 6 simultaneous
> audio streams, amount other things:
> HTMLNewElement.getCapability('audio')

I don't think this would be appropriate for an element. As an API, it's a 
client capability query, which, if we support it, would probably belong to 
an API for doing such things. Not sure what the right spec would be for 
that. Anyone?

-- 
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