Timed Text
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Timed Text refers to the presentation of text media in synchrony with other media, such as audio and video.
Typical applications of timed text are the real time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke, scrolling news items or teleprompter applications.
Timed text for MPEG-4 movies and cellphone media is specified in MPEG-4 Part 17 Timed Text, and its MIME type is specified by RFC 3839.
The W3C has published a Timed Text Markup Language (TTML) specification that covers many aspects of timed text on the Web.[1] SMPTE have created additional metadata structures for use in TTML and developed a profile of TTML called SMPTE-TT[2]. The DECE have incorporated the SMPTE Timed Text in their UltraViolet Common File Format specification.
The issue of developing an interoperable timed text format came up during the development of the SMIL 2.0 specification. Today, there are a number of incompatible formats for captioning, subtitling and other forms of timed text used on the Web. This means that when creating a SMIL presentation, the text portion often needs to be targeted to one particular playback environment. This poses an issue for creating interoperable SMIL presentations. Moreover, the accessibility community relies heavily on captioning to make audiovisual content accessible to a hearing-impaired audience. The lack of an interoperable format adds a significant additional cost to the costs of captioning Web content, which are already high.
Timed Text enriches the user experience for services involving timed text, and is seen as an important stimulus for instance in the usage of captioning and subtitling. The organizations willing to work on Timed Text include vendors of streaming multimedia technology, web browser companies, representatives of the accessibility community, caption content producers and consumer electronics companies.
The following is an extract from the English closed captioning file, in SubRip format, for the 1916 Krazy Kat Bugolist film.
1 00:00:22,000 --> 00:00:27,000 I'll teach thee Bugology, Ignatzes 2 00:00:40,000 --> 00:00:43,000 Something tells me 3 00:00:58,000 --> 00:00:64,000 Look, Ignatz, a sleeping bee
The equivalent in W3C TTML is the following:
<tt xmlns="http://www.w3.org/ns/ttml" xml:lang="en">
<body>
<div>
<p begin="00:00:22" end="00:00:27">
I'll teach thee Bugology, Ignatzes
</p>
<p begin="00:00:40" end="00:00:43">
Something tells me
</p>
<p begin="00:00:58" end="00:00:64">
Look, Ignatz, a sleeping bee
</p>
</div>
</body>
</tt>
[edit] See also
[edit] References
- ^ Glenn Adams (Ed.): Timed Text Markup Language (TTML) 1.0 - W3C Recommendation, 18 November 2010.
- ^ SMPTE (2010-08) (PDF), ST-2052-1; SMPTE Timed Text, Copyright © 2010 SMPTE. August 2010, http://store.smpte.org/product-p/st%202052-1-2010.htm, retrieved 2011-03-25
[edit] External links
- full list of Timed Text files at Wikimedia Commons
- W3C's Video in the Web Activity Statement
- The W3C Timed Text homepage
- Also see DAISY Digital Talking Book standard
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