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[whatwg] Scripted querying of <video> capabilities

From: Eric Carlson <eric.carlson@apple.com>
Date: Thu, 13 Nov 2008 11:19:07 -0800
Message-ID: <58FD84AD-22BE-48FF-9350-4694EF726431@apple.com>

On Nov 13, 2008, at 10:52 AM, Jeremy Doig wrote:

> did this thread go anywhere ?
>

   See http://www.whatwg.org/specs/web-apps/current-work/multipage/browsers.html#dom-navigator-canplaytype 
.



> i'm concerned about the "maybe" case - looks way too much like:
> http://en.wikipedia.org/wiki/DShow#Codec_hell
>
> also - when you probe for mime type, do you mean the entire "type"  
> parameter (including the codecs string) ? for example, there are too  
> many cases where just passing "video/mp4" would be insufficient.  
> (fragmented index support ? base/main/high profile ? paff ? cabac ?)
> <source src="video.mp4" type="video/mp4; codecs=&quot;avc1.42E01E,  
> mp4a.40.2&quot;">
>
   My interpretation is that it does, and the vagueness of many MIME  
types is the reason for the "maybe" case.

eric



> On Wed, Oct 15, 2008 at 11:14 PM, Maciej Stachowiak <mjs at apple.com>  
> wrote:
>
> On Oct 15, 2008, at 1:44 AM, Ian Hickson wrote:
>
>
> On Tue, 14 Oct 2008, Robert O'Callahan wrote:
> On Tue, Oct 14, 2008 at 12:13 PM, Maciej Stachowiak <mjs at apple.com>  
> wrote:
>
> While the underlying media frameworks can't necessarily answer, "if I
> give you a file with this MIME type, can you play it?", they can at
> least give a yes/no/maybe answer, which can still be quite helpful,
> since the UA will know it does not need to check some media streams at
> all.
>
> I agree. If the API lets us answer "maybe", there is not much need or
> temptation to lie, and we can still return information that could be
> useful to scripts.
>
> I have added window.navigator.canPlayType(mimeType). It returns 1,  
> 0, or
> -1 to represent positive, neutral, and negative responses.
>
> This API would be tempting to treat as a boolean but would of course  
> do completely the wrong thing. I think it would be better to either  
> ensure that the positive and neutral responses are both values that  
> JS would treat as true (for instance make the values true, "maybe"  
> and false), or else make all of the return values something self- 
> descriptive and symbolic (for instance the strings "yes", "maybe"  
> and "no"). I think 1, 0, -1 are neither clear nor likely to be in  
> any way beneficial for perforamnce.
>
> Regards,
> Maciej
>
>

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