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WebVTT 1.0 is part of the deliverables of the Timed Text WG

The Timed Text WG charter has been updated in March 2014. It includes delivery of a WebVTT 1.0 specification as a W3C Recommendation.

This means, a snapshot of the WebVTT specification has been taken, FSA commitments have been made, and the specification was submitted to the Timed Text WG as input to the standardization process. All features in this snapshot will now be tested across the different implementations, in particular across browsers. Those features that have been implemented interoperably will be taken to Recommendation over the next year.

This Community Group will continue to work on the WebVTT specification to address new features and collaborate with the Timed Text WG on any bugs found with the submitted specification.

Carriage of WebVTT and TTML in MP4 files

As a result of the 105th MPEG meeting (see Press Release), MPEG has concluded its study of the carriage of Timed Text in the ISO Base Media File Format (MP4). The study resulted in draft standards for the carriage of WebVTT and TTML content that have reached Final Draft stage (FDAM 2 for 14996-12/15444-12 and FDIS for 14496-30).  They are considered complete and are submitted to National Bodies for final vote. This post gives an overview of these draft documents. Continue reading

First Draft of Conversion of 608/708 captions to WebVTT published by Web Media Text Tracks Community Group

On 2013-06-06 the Web Media Text Tracks Community Group published the first draft of the following specification:

Participants contribute material to this specification under the W3C Community Contributor License Agreement (CLA).

If you have any questions, please contact the group on their public list: public-texttracks@w3.org. Learn more about the Web Media Text Tracks Community Group.

WebVTT in Media Transport Formats

WebVTT is quite a powerful format. It has been developed to transport timed data chunks, including captions, subtitles, video descriptions, chapters, and in fact any chunk of data that cues up with a time segment of a media element.

The TextTrack API in HTML5 that provides the means to synchronize timed data chunks with media elements is specified generically such that these cues can come from a <track> element, from JavaScript, or from text tracks provided in-band in a media resource.

The support of WebVTT in <track> elements in browsers is coming along nicely – Safari has released it, IE10, Opera and Chrome have previews and will release it in their next versions, and the Firefox community is also highly active.

As can be expected, support of WebVTT in media transport formats is taking a bit longer to specify and implement. However, we are already seeing specifications for these formats, even though at the time of writing of this article, as far as we know, there are no implementations of any of these specifications yet.

  • WebVTT in WebM was the first specification for encapsulating WebVTT in a media container.
  • WebVTT in Apple’s HTTP Live Streaming has been published just recently and details how to use WebVTT for captions with m3u8. While it right now covers plain cues only and no CSS styling, it is the first format to show how HTTP adaptive streaming formats can make use of WebVTT.

Other formats where we heard that work is happening, but no public specifications have been made available yet include WebVTT in MP4 containers, WebVTT in Ogg, and WebVTT in MPEG DASH.

WebVTT support in browsers

In recent months, several of the big browsers have either released <track> element support with WebVTT or are providing experimental builds with support.

IE 10

Microsoft provided <track> element support in the Internet Explorer 10 Platform Preview 4 to developers on 30th November 2011. IE 10 supports basic versions of both the WebVTT and the TTML format.

The browser preview can be downloaded. A test page has been provided. Documentation is available.

Google Chrome

Google Chrome 18 added <track> element support behind a flag in about November 2011. You can activate it by going to chrome://flags and “Enable element”. Google Chrome only supports WebVTT.

There is extensive documentation at HTML5Rocks.

Safari

Apple released <track> element support in Safari 6 in July 2012. Safari also only supports WebVTT. Like Google Chrome, it builds on the implementation in WebKit, which is trying to be fairly feature-complete for WebVTT.

Opera

In August 2012 Opera released an Opera Next version with WebVTT and <track> support. There is also a Opera Developer blog post on <track> to explain this feature further.

What about Firefox?

Firefox has some work in progress supporting WebVTT, but there aren’t any official builds with support available yet.

In any case: there is still lots to do. Several of the browser implementations don’t support the full feature set yet. Where they do, they may not be interoperable since the spec may have been interpreted slightly differently, or may have changed since the implementation.

We’re starting to create a test suite with example WebVTT files that test different features. The simple “show text at certain time interval” support is certainly interoperable, but some of the more advanced layout features may not be.

It’s certainly time to start experimenting with the feature, even if you may still need a JavaScript polyfill or a specific video player that supports track through other means:

First Draft of WebVTT published by Web Media Text Tracks Community Group

On 2012-08-10 the Web Media Text Tracks Community Group published the first draft of the following specification:

Participants contribute material to this specification under the W3C Community Contributor License Agreement (CLA).

If you have any questions, please contact the group on their public list: public-texttracks@w3.org. Learn more about the Web Media Text Tracks Community Group.

Greetings

Just joined this group. Great to see some faces from the “old days”.

I’m especially interested in using text tracks to support lectures where technical text (especially programming code and markup) is being discussed and illustrated, but I’m also interested in a broader interpretation of ‘text’, for example music scores, mathematical equations, scientific calculations and other non alpha-numerical glyph-based media, which might usefully be synchonised with video.

CG started

Welcome to the newly started “Web Media Text Tracks Community Group” – also by some called the “Captioning CG” or the “WebVTT CG”.

Our work will encompass more than just captioning and more than just WebVTT, therefore the broader title. But we will indeed have a large focus on captioning to begin with and one core aim is to make sure WebVTT offers all the features that a professional captioning format requires.

We will start discussions once representatives of the major browser vendors have joined. It is their implementation work that we want to guide through this group and their questions that we want to address.

Note that I’ve started a WebVTT twitter channel where I am planning to post about the discussion results and spec changes that we make in this CG. If anyone would like to help me with the twitter channel, let me know and I can add you as an author.

I’m looking forward to a flourishing and very productive new CG!