[Playlist] some extensions, timing and meta tracks

[Lucas Gonze]

Hello Łukasz,

> I would like to discuss some changes and extensions to XSPF
> specification.

Let me say in advance that the bar is extremely high for such changes. 
For example, if there were mortal danger.


> I suggest allowing (changing MUST NOT to SHOULD NOT) the user-agent
> usage of duration (4.1.1.2.14.1.1.1.10) element. User should be able to
> force the software to use it.

Very interesting idea!  I see where you're going with this.

The trick is that the semantic of the duration element is not the same one 
you're thinking of.  It is really a query value to aid with content 
resolution.  It is a MUST NOT on using that for any sort of ground truth 
because we didn't want user agents to treat it as display metadata, the 
reasoning being that their own calculations of the duration would be more 
accurate and shouldn't have to clash with the XSPF value.

Your idea is to use this as a performance instruction to the player: 
"Player, perform rendering for $duration milliseconds."

Are you working on a user agent, or is this a theoretical exercise?

Is your intent to build a slide show format?  If so, the trick with XSPF 
is that the media type determines everything about the rendering, so what 
you would do is define a new media type which represents a slide, then 
write a handler for that media type.

-Lucas