[MPEG-OTSPEC] AHG Zoom Meeting announcement and agenda

Tue Dec 12 19:18:12 CET 2023

Dear all,

Thank you for your active participation in the AHG Zoom meeting today. Like
we discussed during the call, we will continue the discussion of remaining
issues offline on this email list and on GitHub (see summary below) and
will reconvene again for another AHG Zoom meeting on January 9, 2024 at
15:00 UTC. This will allow us additional time for final corrections and
clarifications (if needed) to be completed prior to the input contribution
deadline of Jan. 15 [for the next WG meeting taking place on Jan. 22-26,
2024).

Here is a brief summary of the discussion and the resolutions / action
items (my apologies if I missed anything - please feel free to comment on
it):
1. On "Beyond 64K glyph limit" proposed changes
- Introduce new 'MAXP' table tag duplicating both table versions (0.5 and
1.0) and updating data fields as necessary (considering the outcome of any
additional discussions we may have);
- We will not deprecate GSUB contextual substitutions (type 5 and type 7).
- On glyph substitutions: while the number of glyphs in a ligature won't be
affected by increased number of glyphs within a font, the number of
possible ligatures and glyph substitutions may increase as a result of
glyph limit increase. Coverage tables can become quite large - we discussed
and agreed that certain counts and offsets need to be revisited
(potentially changing coverage / classdef offsets from Offset24 to Offset32
data type.
- Font collections: in order to enable the use of new / hybrid fonts as
part of a collection, we agreed to introduce two new TTC header formats
bumping their minor versions to .1 and adding two new fields "numFonts" and
"tableDirectoryOffsets" in each header format.
- COLR table: future changes to accommodate a larger number of base glyphs
would be needed. As an interim solution, in order to enable the use of a
larger number of components we agreed to introduce a new PaintFormat.
- Cubic outlines / control points: while discussing flags (bit 7) we agreed
that unnecessary constraints can be removed allowing the bit7 flag to be
set on both off- and on-curve points. In addition, the current
specification is too concise and may need to clarify runtime behaviour.
- Variable composites: this section will be moved out of the GLYF table
into a separate VARC table. to be drafted and presented for review and
offline discussion by the end of this week (before or on Dec. 15).
2. Working Draft updates:
- Previously discussed and agreed changes for representative instance and
condition value proposals have been introduced in the last revision; there
are additional changes needed to address technical issues in the Condition
Table specification (2nd paragraph, see comment in the WD text). Peter C.
will review the spec changes that were introduced as part of OT 1.8.4 / 1.9
updates and prepare an input contribution to address this and other
portions of the OFF.
3. Extra topics:
- We discussed the possibility of making CPAL optional to allow having
COLR table without CPAL;
- There was a brief discussion of a prior attempt to introduce 'dmap' (as
in delta 'cmap') table for use in TTCs.
- Previously, we started the discussion of the "Feature variations: New
substitution mechanism" document as part of the Portland AHG meeting in
August; we ran out of time and failed to discuss it during the AHG meeting
in September and postponed it until after the October WG meeting. Skeff
will prepare a draft proposal outlining the spec changes, and we will
review and discuss it both offline and at the upcoming Jan. 9 AHG Zoom call.

I will send a new meeting invite with the updated agenda for Jan. 9 Zoom
call no later than Dec. 22nd.

Thank you,
Vladimir

On Fri, Dec 1, 2023 at 2:43 PM Vladimir Levantovsky <
vladimir.levantovsky at gmail.com> wrote:

> Dear all,
>
> This is just a friendly reminder that we will have the AHG Zoom meeting in
> just over a week from now, on Dec. 12.
> Please review the agenda and the documents linked to each agenda item, and
> prepare your comments ahead of time - this will help us make our meeting
> time more productive [and, hopefully, shorten the meeting time to better
> accommodate our Japanese participants who will be joining late at night].
>
> Thank you,
> Vladimir
>
>
> On Wed, Nov 22, 2023 at 1:48 PM Vladimir Levantovsky <
> vladimir.levantovsky at gmail.com> wrote:
>
>> Dear all,
>>
>> According to the AHG mandates I shared earlier, we will hold the AHG Zoom
>> meeting on Dec. 12, 2024 at 15:00 UTC to review the proposed changes
>> outlined in the "Technologies under consideration for ISO/IEC 14496-22
>> 5th edition Open Font Format
>> <https://www.google.com/url?q=https://www.mpeg.org/wp-content/uploads/mpeg_meetings/144_Hannover/w23265.zip&sa=D&source=calendar&usd=2&usg=AOvVaw25m9Ay4YP6_EiDUnFEMAwA>"
>> document, and review the current version of the Working Draft of the 5th
>> edition ISO/IEC 14496-22. Please see below the new Zoom meeting info and
>> agenda, and please review the documents ahead of time to make the use of
>> AHG meeting time most efficient and productive. (The meeting is scheduled
>> for two hours but I hope that we will be able to accomplish our goals ahead
>> of time.)
>>
>> The AHG meeting will be held under the following ISO rules and policies:
>> - Declaration for participants in ISO activities
>> <https://www.google.com/url?q=https://www.iso.org/declaration-for-participants-in-iso-activities.html&sa=D&source=calendar&usd=2&usg=AOvVaw2n2ZhkFMkQBjPrst6wyAbi>
>> - ISO Code of Ethics and Conduct
>> <https://www.google.com/url?q=https://www.iso.org/files/live/sites/isoorg/files/store/en/PUB100011.pdf&sa=D&source=calendar&usd=2&usg=AOvVaw3R7JNkexzilX-qCtg_vrzR>
>> - Guideline for Implementation of the Common Patent Policy for
>> ITU‑T/ITU‑R/ISO/IEC
>> <https://www.google.com/url?q=https://www.iso.org/files/live/sites/isoorg/files/developing_standards/resources/docs/20221216_Guidelines_for_Implementation_of_the_Common_Patent_Policy.pdf&sa=D&source=calendar&usd=2&usg=AOvVaw3236BoeE5tQKR46VIx_R2a>
>>
>> Agenda
>> 1. Overcoming 64K glyph limit and other updates.
>> The content of the proposal summarized by the "Technologies under
>> consideration for ISO/IEC 14496-22 5th edition Open Font Format
>> <https://www.google.com/url?q=https://www.mpeg.org/wp-content/uploads/mpeg_meetings/144_Hannover/w23265.zip&sa=D&source=calendar&usd=2&usg=AOvVaw25m9Ay4YP6_EiDUnFEMAwA>"
>> document has been updated by authors to accommodate comments and
>> corrections discussed during the WG Font break-out group session - please
>> review the changes:
>> https://github.com/harfbuzz/boring-expansion-spec/blob/main/iso_docs/WG03-beyond-64k-glyphs-2023-11-20.pdf
>> <https://www.google.com/url?q=https://github.com/harfbuzz/boring-expansion-spec/blob/main/iso_docs/WG03-beyond-64k-glyphs-2023-11-20.pdf&sa=D&source=calendar&usd=2&usg=AOvVaw06F5OqaCXHnNNtH0YMmg7N>
>>
>> Goal - review and discuss proposed table changes, and provide AHG
>> recommendations;
>>
>> 2. Review the text of the updated WD of ISO/IEC 14496-22 5th edition
>> Open font format
>> <https://www.google.com/url?q=https://www.mpeg.org/wp-content/uploads/mpeg_meetings/144_Hannover/w23170.zip&sa=D&source=calendar&usd=2&usg=AOvVaw20amv1y6ikAAZdkad37arZ> that
>> incorporates previously adopted changes to Condition Value and
>> Representative Instance proposals.
>> - Review tracked changes;
>> - Review and discuss the current description of the Condition Table (2nd
>> paragraph in particular, see comment in the WD text in subclause 6.2.9) that
>> is technically incorrect since it is referring to non-existent version
>> number of the ConditionSet table.
>> Goal - provide AHG recommendation / future updates.
>>
>>
>> Zoom meeting info: REDACTED
>>
>> Due to public availability of the email list archive, the meeting info
>> cannot be shared on the list. All AHG members who previously joined AHG
>> meetings in the past were already invited to attend.
>> If you did not receive the invitation and would like to attend, please
>> contact me directly.
>>
>
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