W3C home > Mailing lists > Public > public-html@w3.org > February 2013

RE: Proposed extension to HTML5.1 for rollup captions

From: Paul Cotton <Paul.Cotton@microsoft.com>
Date: Wed, 20 Feb 2013 20:28:42 +0000
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: public-html <public-html@w3.org>
Message-ID: <AB5704B0EEC35B4691114DC04366B37F202A6710@TK5EX14MBXC295.redmond.corp.microsoft.com>
> One proposals was picked and developed further: http://www.w3.org/community/texttracks/wiki/MultiCueBox

Has the TextTracks Community Group published a  Final Specification and has the W3C issued a call for participants to sign the Final Specification Agreement<http://www.w3.org/community/about/agreements/final> [1] for that Final Specification?  Shouldn't this be done before the material is adopted into the HTML WG?

HTML WG co-chair

[1] http://www.w3.org/community/about/agreements/

Paul Cotton, Microsoft Canada
17 Eleanor Drive, Ottawa, Ontario K2E 6A3
Tel: (425) 705-9596 Fax: (425) 936-7329

From: Silvia Pfeiffer [mailto:silviapfeiffer1@gmail.com]
Sent: Wednesday, February 20, 2013 12:57 AM
To: public-html
Subject: Proposed extension to HTML5.1 for rollup captions

Hi all,

This is a proposal to extend the TextTrack API in HTML with new objects that will enable the display of captions/subtitles as scrolling text, and introduce the ability to move a group of caption/subtitle cues from one location on the video viewport to another. The feature will allow presenting rollup captions from all text track formats that a browser supports, including WebVTT and TTML.

Specification: https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/region.html#extension-of-the-html-texttrack-api
(Only the Appendix is relevant to the HTML WG).

I'm looking for feedback on this feature here. If there are no objections and sufficient support for these features, I suggest adding them to the HTML5.1 specification.

The use case:
Summary: Video users of diverse nations are used to the use of rollup captions from TV. Deaf users have asked to have all TV content be displayed on the Web in the same format. In the US it is a legal requirement to support rollup captions on all video devices.

The display of captions/subtitles as scrolling text is known as "rollup captions" (e.g. [0]). It is one of three standard display styles for captions on TV [1]. It is often used when material is live captioned and for post-production broadcast programming that only has one speaker. [2]

Rollup is part of the Consumer Electronics Association specifications of captioning for analog TV (CEA608) and for digital TV (CEA708). It is not only supported on TV but also on DVD through the SCC format [4]. It is used in the US, Canada [5], Australia, and probably other countries. The QuickTime file format supports it (e.g. [6]).

Rollup captions on all video devices, including devices that display Web content, are a legal requirement in the US, introduced through the Communications and Video Accessibility Act (CVAA) by the Federal Communications Commission (FCC) 79.103 [7].

The proposal:
Summary: Introduce a TextTrackRegion object that is a video viewport region and can hold multiple TextTrackCues. The properties of TextTrackRegion specify the display location and text scrolling mechanism for the cues it contains.

In the TextTracks Community Group we have analysed how to introduce rollup captions using WebVTT and the HTML <track> element.

11 different proposals were analysed: http://www.w3.org/community/texttracks/wiki/RollupCaptions .

One proposals was picked and developed further: http://www.w3.org/community/texttracks/wiki/MultiCueBox
There is a trial implementation in JavaScript for WebVTT: https://github.com/silviapfeiffer/WebVTT-with-regions
Example rendering: http://html5videoguide.net/test/WebVTT-with-regions/player.html (needs a browser that supports TextTrack, so don't use Firefox).

An experimental implementation in WebKit is forthcoming: https://bugs.webkit.org/show_bug.cgi?id=109570

Note: Ian Hickson is not supportive of this feature in WebVTT: https://www.w3.org/Bugs/Public/show_bug.cgi?id=20349 and recommends browsers to implement SCC [4] support instead. However, the objects proposed in this extensions specification would still be required to represent the feature.

Are there any objections towards introducing these extensions into HTML5.1?

[0] http://www.slideshare.net/prithviraj_karbar/roll-up-captions-sample
[1] http://www.dcmp.org/caai/nadh38.pdf
[2] http://abercap.com/blog/2009/03/17/understanding-the-differences-between-roll-up-captioning-pop-on-captioning-and-subtitling/
[3] http://www.atsc.org/cms/standards/a53/a_53-Part-3-2009.pdf
[4] http://www.theneitherworld.com/mcpoodle/SCC_TOOLS/DOCS/SCC_FORMAT.HTML
[5] http://www.cab-acr.ca/english/social/captioning/captioning.pdf
[6] http://zeitanker.com/common/movies/PedPoster.mov
[7] http://www.hallikainen.com/FccRules/2012/79/102/index.php

Best Regards,
Received on Wednesday, 20 February 2013 20:30:06 UTC

This archive was generated by hypermail 2.3.1 : Thursday, 29 October 2015 10:16:31 UTC