Re: [Cellar] [ietf-wg-cellar/ebml-specification] EBML ID 0x80 is marked invalid/reserved but it's used in Matroska (#407)

Adding our Loyal AD ... because I could be wrong, and he would know ...

On Mon, May 10, 2021 at 9:16 AM Michael Richardson <mcr@sandelman.ca> wrote:

>
> Steve Lhomme <notifications@github.com> wrote:
>     > As pointed out by [Paul Foley](
> https://mailarchive.ietf.org/arch/msg/cellar/z_INjU-Vc9FOTDZs9AhdRRjrIig/),
> the 0x80 is EBML ID is said to be invalid in the [RFC text](
> https://datatracker.ietf.org/doc/html/rfc8794#section-5):
>
>     >> The bits of the VINT_DATA component of the Element ID MUST NOT be
> all
>     >> "0" values or all "1" values.
>
>     > But in Matroska we use 0x80 for `ChapterDisplay`.
>
>     > I think the all 0 rules should be removed. In particular because 0x80
>     > is the value that should be used when all VINT_DATA bits are 0, per
>     > this rule:
>
>     >> The VINT_DATA component of the Element ID MUST be encoded at the
> shortest valid length.
>
>     > Changing this text means also editing the IANA registry which lists
> all
>     > the variants of 0 bits as reserved.
>
> I'm not sure how to deal with this.
> It may be that we can put these IANA instructions into the Matroska
> document.
> Obviously, they would ideally go into an EBML-bis document, and that would
> be
> something we'd do if we were revising it now.
>

That would be perfect (if we were doing an EBML-bis document, but I predict
that the answer is - the EBML document is a Proposed Standard, so any
Proposed Standard that (reasonably) updates the instructions to IANA should
be OK. This update is relevant for Matroska, which is also targeting
publication as a Proposed Standard, so that's a fine place to put the
updated IANA instructions.

The EBML RFC IANA instructions would be outdated, but the point of IANA
registries is that the IANA registries are up to date, and you don't have
to chase (in some cases) a few dozen RFCs to find all the rules.

Murray, is that about right?

Best,

SPencer

> IANA instructions are a bit weird in that they are in essence,
> edge-triggered, and once processed in a document, they change.
>
> ( https://en.wikipedia.org/wiki/Interrupt )
>
> --
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