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Timed Text Markup Language
Timed Text Markup Language (TTML), previously referred to as Distribution Format Exchange Profile (DFXP), is one of W3C's standards regulating timed text on the internet.
In 2010, after discussions about its adoption in HTML5, WHATWG opted for a new but more lightweight standard based on the popular SRT format, now named WebVTT.〔(【引用サイトリンク】title=WebVTT versus TTML: XML considered harmful for web captions? )〕 Nonetheless, in February 2012 the FCC declared SMPTE closed-captioning standard for online video content, a superset of TTML, as "safe harbor interchange, delivery format"〔(【引用サイトリンク】title=FCC Declares SMPTE Closed-Captioning Standard For Online Video Content As Safe Harbor Interchange, Delivery Format )〕
It is not clear whether the HTML5 specification will document the usage of any other timed text format with the <track> tag. However, as of February 2015, W3C only documents the usage of WebVTT with HTML5 and its specification had 434 entries in its commit history, ranging from March 2013 to January 2015, while the latest TTML specification hadn't been modified since September 2013. Recent versions of Internet Explorer introduced support for TTML files in the <track> element,〔(【引用サイトリンク】title=Simple Delivery Profile for TTML Captions )〕 while other browsers still require Javascript, such as in the W3C Timed Text Working Group's (2009 demo ) of DFXP features. TTML is still the format of choice for some applications that don't rely on HTML5, such as the popular set-top box Roku.〔(【引用サイトリンク】title=Roku Closed Caption Support )〕
== Profiles ==
The DFXP standard specified a wide range of features, many of which are not necessary for specific applications. For this reason, the standard developed the concept of profiles, which are subsets of required features from the full specification. This way, a player that only implements a partial set of features, for example, can define its own profile and claim support to it. The specification was thus renamed to TTML, accounting only to the markup language, and defined three standard profiles: DFXP Transformation, DFXP Presentation and DFXP Full. Not satisfied with the list of features defined by TTML, the Society of Motion Picture and Television Engineers (SMPTE) created its own profile, which extended the full DFXP profile and defined new features, not included in the TTML specification.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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