Re: Processor Profile, Content Profile and codecs

Le 07/10/2015 17:48, Glenn Adams a écrit :
> Document Interchange Context abstracts the delivery context, allowing, 
> for example, the envelope or container to specify a profile without 
> doing so in the document itself. Though I would always prefer the 
> document to do so.
I agree, it is very fragile to specify the profile outside of the 
document because the information might get lost in a workflow, or worse 
become invalid.

>
> As for finding what processor profile applies to a document, it is 
> rather more complicated than simply looking for a ttp:profile 
> attribute, even in TTML1.
That's what I fear.
> This is because it is possible to declare a profile within the 
> document instead of by reference, i.e., by using the ttp:profile element.
Well, I think this is a bit over-engineered. You can't build a video 
stream saying I use this feature from this profile and that feature from 
that other profile. You indicate the smallest profile that supports all 
features.

>
>             - the ttp:profile element does not have a designator
>             attribute.
>
>         What would a designator attribute be for? Features have
>         designators, not
>         profiles. There is a use attribute though.
>
>     According to the registry, profiles have designators. According to
>     5.2 in TTML1, profiles have designator. It seems very hard to
>     determine if a document can be played by a player by inspecting
>     all features to see if they match existing profiles.
>
>
> Not really. This has been implemented multiple times without 
> difficulty. The process works as follows:
>
>   * determine the effective processor profile EPP that applies to
>     document D
>   * for each feature F in EPP
>       o if F is required, but not supported, then abort processing
>         unless abort is overridden
>   * for each extension E in EPP
>       o if E is required, but not supported, then abort processing
>         unless abort is overridden
>
> There is nothing difficult about this process.
Difficult might not be appropriate word. Not affordable might be better. 
I want a *simple* way to find the profile. Checking each feature, each 
extension is too much for me.

I'm considering applying the following algorithm, to find the profile 
identifier(s) to produce the codecs:
- if the document is TTML1,
     - if the ttp:profile attribute is present, use it
     - if ebutt:conformsToStandard exist, use them and combine them
     - otherwise return a full profile (which one?)
- if the document is TTML2,
    - if the ttp:processProfiles is present, use it
    - if ttp:profile elements with designators are present, use them and 
combine them,
    - otherwise return a full profile

Would that work?

Cyril

-- 
Cyril Concolato
Multimedia Group / Telecom ParisTech
http://concolato.wp.mines-telecom.fr/
@cconcolato

Received on Thursday, 8 October 2015 07:54:15 UTC