[whatwg] Serving up Theora <video> in the real world

Philip Jägenstedt philipj at opera.com
Sat Jul 11 08:44:25 PDT 2009

On Sat, 11 Jul 2009 14:38:02 +0200, Robert O'Callahan  
<robert at ocallahan.org> wrote:

> On Sat, Jul 11, 2009 at 11:51 PM, Philip Jägenstedt  
> <philipj at opera.com>wrote:
>> Yes, I'm saying that when codecs are provided true means "probably" and
>> otherwise it means "maybe", because the distinction is pointless.
> IIRC some browsers using system media frameworks don't know what codecs  
> they
> support, so they still need to be able to answer "maybe" when codecs are
> provided; you still need a three-valued result.

Opera is one such browser (when using GStreamer), but even if we return  
"maybe" for "video/ogg; codecs=uncertain-codec", what could be done with  
the information? The only way of knowing is trying to play it, which is  
what the resource selection algorithm would do. That's true of both  
"maybe" and "probably", neither are actual guarantees. Is there any use  
case for distinguishing them? This is primarily a disagreement about what  
kind of API is more aesthetically pleasing, either way exposes the same  
(useful) information.

> I still think it would confuse authors if you return true for  
> canPlayType(T)
> and false for canPlayType(U) where U is a subset of T.

"video/ogg; codecs=vorbis" (U) is not a subset of "video/ogg" (T) as the  
codecs in T is the empty set, not the set of all codecs. Or did you have  
some other values of U and T in mind?

Philip Jägenstedt
Core Developer
Opera Software

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