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Re: detecting caption files?

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From: John Foliot
Date: Jan 11, 2018 8:55AM

Hi Diane,

Caption files can be tricky things, because there is more than one way of
supplying them on a site: you can use the @track attribute (out of band),
OR, using the appropriate API, the captions can be delivered "in-band".

File formats such as .mp4 and .mkv are "wrapper formats" - containers for
multiple pieces of content (think similar to a .zip file - not exactly, but
a good approximation...). So, for example, an .mp4 file actually contains a
video encoded using a codec like H.264, and audio track using something
like AAC encoding, and... if created properly, the content creator can also
include other content files inside the .mp4 file, like the time-stamped
caption file (.vtt). Placing caption files 'inside' of an .mp4 file happens
at the post-production level (i.e. the video creation tool/suite).

I can double check with Deque's engineers if aXe is programmed to examine
'inside' of MP4 files looking for a caption file, and if so, how, but I
also recall that YouTube also uses a proprietary time-stamp format for
their captions, so if aXe is only looking for WebVTT or TTML
markup/time-stamp formats, it *might* be missing the proprietary format.
(Just a guess at this time).

For testing purposes today, I would recommend you continue with manual
tests: nother requirement is that the end-user can toggle the captions on
or off (when provided as closed captions), and that control/button needs to
also work from the keyboard only, so traditionally when I am testing a
video region/player, I do all the tests (manual and mechanical) at one
time, so, can you toggle captions on or off via the keyboard only will also
determine whether captions exist or not ;)

HTH

JF

On Thu, Jan 11, 2018 at 9:26 AM, Tomlins Diane <
<EMAIL REMOVED> > wrote:

> Hello everyone :)
> Does anyone know of a tool that is able to detect whether or not a caption
> file exists on videos?
> I know that aXe will flag that it can't find a caption file, but when I
> tried it on YouTube, on a video I know has no caption file, it didn't flag
> anything.
>
> Thanks!
>
> Diane R Tomlins
> HCA IT&S | Digital Media
> Accessibility SME
>
>
>
> > > > >



--
John Foliot
Principal Accessibility Strategist
Deque Systems Inc.
<EMAIL REMOVED>

Advancing the mission of digital accessibility and inclusion