Timed Text
Encyclopedia
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.
SMPTE have created additional metadata structures for use in TTML and developed a profile of TTML called SMPTE-TT. 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>
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
Teleprompter
An autocue is a display device that prompts the person speaking with an electronic visual text of a speech or script. Using a teleprompter is similar to the practice of using cue cards...
applications.
Timed text for MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
movies and cellphone media is specified in MPEG-4 Part 17 Timed Text
MPEG-4 Part 17
MPEG-4 Part 17, or MPEG-4 Timed Text, or MPEG-4 Streaming text format is the text based subtitle format for MPEG-4, published as ISO/IEC 14496-17 in 2006...
, 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.
SMPTE have created additional metadata structures for use in TTML and developed a profile of TTML called SMPTE-TT. 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
Synchronized Multimedia Integration Language
SMIL , the Synchronized Multimedia Integration Language, is a W3C recommended XML markup language for describing multimedia presentations. It defines markup for timing, layout, animations, visual transitions, and media embedding, among other things...
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
Streaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
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
SubRip
SubRip is a software program for Windows which "rips" subtitles and their timings from video. It is free software, released under the GNU GPL...
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="
<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>
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 standardDAISY Digital Talking BookDAISY is a standard for digital talking books. DAISY books are typically used by people have "print disabilities," including blindness, impaired vision, dyslexia...