Re: [web-audio-api] decodeAudioData should accept a mime-type (#7)

> [Original comment](https://www.w3.org/Bugs/Public/show_bug.cgi?id=18510#10) by Philip Jägenstedt on W3C Bugzilla. Tue, 28 Aug 2012 15:08:27 GMT

(In reply to [comment #10](#issuecomment-24244121))
> (In reply to [comment #9](#issuecomment-24244116))
> > (In reply to [comment #8](#issuecomment-24244108))
> > > I would also prefer decodeAudioData to accept a non-optional mimeType argument,
> > > and I think we raise an error if the mimeType argument is not supported by the
> > > engine.  The reason that I would advocate for this change is that the audio
> > > codecs supported by each engine (potentially on each platform) is different,
> > > and that makes sniffing even worse than it already is.
> > 
> > Can you clarify how varying codec support between browsers and platforms make
> > sniffing any harder? AFAIK, none of the formats supported by any browser are
> > hard to sniff or possible to mistake for another supported format.
> 
> They won't make sniffing harder -- it just makes people rely on sniffing
> potentially multiple audio streams, which means that the browser engine needs
> to download the first few kilobytes of all of them until it finds one which it
> can decode.
> 
> The idea that I'm going after is very similar to the HTML5 source element.  The
> source element allows the browser engine to select the encoding that it
> supports *without* needing to download all of the available resources and sniff
> them.  If decodeAudioData takes a mimetype argument, then the browser engine
> can also avoid having to download the resource just to find out that it cannot
> decode it.

decodeAudioData takes an ArrayBuffer, so by the time you can call it you have already downloaded the data. I think that using HTMLMediaElement.canPlayType() to determine which format is supported and only downloading that data ought to be sufficient.

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