Re: [Cellar] Experimental elements

Steve Lhomme <slhomme@matroska.org> Sun, 24 June 2018 13:31 UTC

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From: Steve Lhomme <slhomme@matroska.org>
Date: Sun, 24 Jun 2018 15:31:55 +0200
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To: Codec Encoding for LossLess Archiving and Realtime transmission <cellar@ietf.org>
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Subject: Re: [Cellar] Experimental elements
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PS: I apologize in advance but I won't be able to make it to the
CELLAR virtual meeting on Tuesday, I have previous commitments to
attend.

2018-06-24 15:30 GMT+02:00 Steve Lhomme <slhomme@matroska.org>rg>:
> As discussed in
> https://github.com/Matroska-Org/ebml-specification/issues/157 We need
> a clean way to define experimental elements. So that new elements can
> be added/tested while not having to iterate the DocType version each
> time. Especially as the they are meant to be backward compatible as
> much as possible.
>
> I added to proposal on GitHub:
> - https://github.com/Matroska-Org/ebml-specification/pull/180 a simple
> DocType sub-version that allows iteration between different versions
> before new elements are finalized in a new DocTypeVersion.
>
> - https://github.com/Matroska-Org/ebml-specification/pull/181 a list
> of DocTypeExtension which allow different groups to work on different
> subsets of elements, each with their own name (or workgroup or
> namespace).
>
> In any case elements from each proposal don't have to be handled so
> long as the EBML Reader can handle the DocTypeReadVersion. But if they
> can, it's nice.
>
> Following this concept, I wonder if Tags could exist as a Matroska
> Extension, possibly not part of the main DocTypeVersion at all.
>
> Jerome wanted some extra elements, this could be done this way as well
> in a clean way.
>
> Note that an extension version depends on the DocTypeVersion it's in.
> So moving from matroska v4 to matroska v5, each "independent"
> extension should have an update if they want to keep working. Or we
> could not do that at all and allow extensions having a life of their
> own. Maybe there could be 2 types of extensions: those which goal is
> to be merged in the main DocTypeVersion, those standalone.
>
> The DivX elements are good examples of extensions that could leave on
> their own. And we wouldn't have to put them in the main spec and
> wonder how they could work. On the other hand these old files don't
> advertise this extension...
>
> --
> Steve Lhomme
> Matroska association Chairman



-- 
Steve Lhomme
Matroska association Chairman