Fwd: Conversion of 608/708 captions to WebVTT - how to map the colour green

FYI

---------- Forwarded message ----------
From: Michael Borthwick <mb@michaelborthwick.com.au>
Date: Mon, Mar 24, 2014 at 7:16 PM
Subject: Conversion of 608/708 captions to WebVTT - how to map the colour
green
To: public-texttracks@w3.org


Dear List Members,

I am Australian media engineer who wrote a technical paper, presented last
year at the SMPTE 2013 Conference in Sydney, entitled "It's not easy being
green - a closed captioning for web case study'.
This dealt with the making some hundreds of closed captioned video clips
available on a client web site in 2011 using DFXP format and JW player.
One of a number of hurdles that were overcome in that project was gaining
an understanding of, and overcoming, an apparent semantic difference
between the colour green when used for closed captions and subtitles in the
broadcast industry and that on the web.

To speak to the essence of a 5 page technical paper I formed the opinion
that it is the intention in the broadcast world, in standards such as
CEA608/708 and the European DVB standard (used in Australia) that the
colour green means that the green value be at its maximum ie in 8 bit RGB
(decimal) 0 255 0.

Colour captions are commonly used in Australia to distinguish between
speakers and are particularly relevant to clarify meaning for the Deaf or
hearing impaired viewer when the speaker is off screen - although green is
arguably the least common of the four colours used.

Literally translating the occurrence of 'green' from a broadcast standard
into a web caption standard that leverages CSS specifications for green of
RGB  (hexadecimal) 008000 yields a darker green with inadequate contrast as
the green channel is not at its maximum.

I would therefore respectfully suggest that the WebVTT Community Group, in
common with others developing cross-domain conversion standards, revisit
the assumption that CEA608 and 708 colours 'map to CSS colors of the same
name' as suggested in Clause 1.6 of the Draft of the conversion document at
https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html

If the desire is to map to a named colour then a more appropriate named
colour might be 'lime' in order to more accurately capture what I believe
to be the broadcast intent.

it is my understanding, based on personal communication with engineers from
the BBC undertaken after the conclusion of my project, that this is the
parsing used when caption files in broadcast formats are mapped for web
display on the BBC's many public-facing platforms.

While the slides from my presentation are available from my LinkedIn
profile, and the paper was made available to conference to attendees, is
not publicly available on the web.
However I am happy to respond to requests off-list should it be of interest
to individual members of the Community Group.

Thankyou for your interest in this important area of web accessibility.



Thanks,

Michael




Michael Borthwick Consulting Pty. Ltd.
GPO Box 1950, 380 Bourke Street, Melbourne Australia 3001
Level 1, 384 Bridge Road, Richmond
Mobile Ph: + 61 418 345 800
http://www.michaelborthwick.com.au