Magnified Caption Files

(copying the WCAG Low Vision TF)

All,

As you are possibly aware, we are currently closing off some old comments
with the VTT Working Group (with spill-over to the TTML / IMSC Working
Group) around the ability to enlarge caption text to support Low Vision
users.

Sylvia Pfeiffer responded with the following:

If I understand correctly, you'd like me to add authoring guidance around
magnification and its potential impact.

Could it be done with a single paragraph such as:
*"Authors of WebVTT caption and subtitle files are encouraged to test the
rendering of their files using Assistive Technology. Specifically, the use
of magnification tools by low-vision users may require editing their files
to allow for sufficient space within cue lines and cue line heights. It is
recommended to allow for a 200% magnification without clipping."*

My personal opinion is that this is effectively what we seek (Ref: WCAG SC
1.4.4 Resize Text), but before I respond more formally to the GitHub issue (
https://github.com/w3c/webvtt/issues/426) I'd welcome some feedback.

LVTF, does this sound right? LV members, have you encountered something
like this previously? (the ability to enlarge caption files independent of
the video?)

APA - are we comfortable with Sylvia's proposal? Would something like this
also meet our needs with the TTML / IMSC group?

Given that the VTT WG are keen on disposing with all comments, I'd like to
try and resolve this one fairly quickly.

Thoughts?

JF
-- 
John Foliot
Principal Accessibility Strategist
Deque Systems Inc.
john.foliot@deque.com

Advancing the mission of digital accessibility and inclusion