[MPEG-OTSPEC] Note on VARC conditions and condition set negation

[Behdad Esfahbod]

I won't be making any changes for next week. Will work for the next
deadline, if there's any.

behdad
http://behdad.org/


On Thu, Apr 11, 2024 at 5:42 PM Skef Iterum via mpeg-otspec <
mpeg-otspec at lists.aau.at> wrote:

> I guess I can answer my own question here: You have your current
> proposal document and we have newfeatvar_spec.pdf. If you want to
> propose this change for the April working group meeting *cleanly* you can
> do that by making an *additional* proposal *against* those two documents,
> and emailing it here first. (newfeatvar_spec has all of the relevant VARC
> content because of the editorial direction I took with it.)
>
> That would presumably propose to:
>
>    1. Eliminate condition formats 2 and 4 from newfeatvar_spec.
>    2. Change format 3 back to 2.
>    3. Add the three additional formats.
>    4. Note in the condition set section that that mechanism has been
>    partially superseded
>    5. Make the appropriate changes to 6.2.10.
>
> This way the alternate system is genuinely severable from the
> content that has already been discussed and approved as part of the
> Ad Hoc process.
>
> I've already indicated what some of the 6.2.10 changes would be,
> but they are:
>
>    1. The LookupCondition record now just has a conditionOffset and a
>    lookupIndexListOffset, from which lookups are taken when the
>    (now potentially compound) condition at that offset is true.
>    2. Assuming we're eliminating the condition set, you'll need to note
>    somewhere appropriate that a 0 offset to a condition means the
>    condition is true (as is true of condition sets).
>
> I don't recommend getting rid of the conditionSet in the
> FeatureVariationRecord
> because of the versioning issues that would introduce.
>
> This still raises a lot of questions about lack of input and very short
> engineering
> time, but it means that people could take it or leave it at the meeting on
> its
> merits, rather than feeling pressured by it's sudden inclusion in a
> document
> already tracked for approval.
>
> Skef
> On 4/11/24 16:09, Skef Iterum via mpeg-otspec wrote:
>
> The current newfeatvar_spec document has the negated conditions and
> reorders the section on condition sets and conditions. This sort of
> addition would need coordination between the two documents. I'm on PTO
> Friday through Monday. How is this going to happen before the 17th?
>
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