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

Robert O'Callahan robert at ocallahan.org
Sun Jul 12 14:46:31 PDT 2009

On Sun, Jul 12, 2009 at 3:44 AM, Philip Jägenstedt <philipj at opera.com>wrote:

> 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?

Reject that type in favour of a type for which canPlayType returns
"probably", or reject that type in favour of plugin-based fallback.

System media frameworks need to start exposing which codecs they support, if
they don't already. In the meantime, you can probably identify a minimal set
of codecs that the framework definitely supports.

> 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.

No, "video/ogg" means the codecs are unspecified, not that no codecs are
used. As soon as you add a "codecs" parameter, you are promising that those
are all the codecs needed by the file. So every file that's "video/ogg;
codecs=vorbis" is also "video/ogg".

"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
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