On Fri, 10 Jul 2009 19:23:44 +0200, Aryeh Gregor
<simetrical+...@gmail.com> wrote:
On Fri, Jul 10, 2009 at 4:57 AM, Robert O'Callahan<rob...@ocallahan.org>
wrote:
The way we've implemented in Firefox, we'll return "yes" if you specify
a
codecs parameter and we support every codec in your list. So
v.canPlayType("video/ogg; codecs=vorbis,theora") returns "probably" in
Firefox 3.5. I think this is reasonable because I believe that, modulo
bugs
in our implementation, we support the full Theora and Vorbis specs. On
the
other hand, we will return "maybe" for v.canPlayType("video/ogg"). I
think
this distinction will be useful.
In what use-case would an author want to make use of the distinction?
In either case, your only course of action is to try playing the
video. Maybe you'd try testing all the video types you support, and
if one is "maybe" while another is "probably" you'd go with
"probably"? That seems like a pretty marginal use case to help for
the sake of such a confusing API. Programmers expect binary logic,
not ternary (look at the complaints about SQL's NULL).
I agree that the current interface is ugly and quite fail to see what the
use for it is. With a boolean return value, canPlayType("application/ogg")
would return true if one can demux Ogg streams.
canPlayType("application/ogg; codecs=vorbis,dirac") would return true if
one can demux Ogg and decode vorbis + dirac. Differentiating between
"maybe"/"probably" really seems like an edge use case, but you could if
you really wanted to:
function tertiaryCanPlayType(mime) {
[container, codecs] = mime.split(";");
if (canPlayType(mime)) {
return codecs ? "probably" : "maybe";
} else {
// if there are codecs, canPlayType(container) would tell you if
problem is with the container format or the codecs
return ""; // was "no"
}
}
Unless there's some compelling use case that can't be handled with the
above I'd support canPlayType returning a boolean. The only issue I can
see is that canPlayType(foo)==true might be interpreted as a strong
promise of playability which can't be given. In that case just rename the
function to wouldTryTypeInResourceSelection (no, not really).
--
Philip Jägenstedt
Core Developer
Opera Software
