User:Cwmwenallt/SMPTE-TT

SMPTE Timed Text (SMPTE-TT) is a declarative XML-based application of W3C TTML created by SMPTE. SMPTE-TT can be used in modern studio workflows to deliver new high resolution captions or subtitle data over IP networks with improved presentation features, and can be also used to convert legacy data such as CEA-608 or EBU STL.

The key features of SMPTE-TT are
 * More creative freedom compared to legacy formats
 * is XML-based so that content can be formally checked and errors easily detected in a file based workflow
 * can be transported in MXF (ECI-HIPS-MXF)
 * supports the use of subtitles in the web
 * is easily handled by content management systems
 * is already implemented in most subtitling systems (export)
 * can be easily converted to from other formats

The document, formally called SMPTE ST 2052-1:2010, Timed text Format (SMPTE-TT) is part of a series of documents, all of which are made freely available by SMPTE. The first part is the "Roadmap for Format Translation". The main specification SMPTE ST 2052-1:2010 "SMPTE Time Text Format" and the recommended practice  SMPTE ST 2052-10:2010 "Conversion from CEA-608 Data to SMPTE-TT" are also available without charge at the SMPTE Digital Library.

The SMPTE additions include a method to "tunnel" legacy formats within in the XML for example CEA 608 -- so that a receiver that was parsing the XML could also 'un-tunnel' the 608 if the equipment had a composite analog video output to feed a standard television; this feature is unprecedented in broadband caption implementations and has the potential to greatly help the hearing impaired community as they may have legacy boxes that expect “classic” analog waveforms and do not have new devices.

A second addition is also the ability to support graphical pre-formatted captions (for example to convert from used in DVD and Asia) which is not supported in W3C TTML 1.0.

W3C TTML, and hence SMPTE-TT is built around support of international character sets through Unicode and has other expansion capabilities that some of the legacy standards lack. It supports international layout.

An important role of SMPTE-TT is to function as a modern exchange format to repurpose the vast library of existing captioned content (currently stored as CEA 608, EBU STL and so on), unification of exchange is key to cost-reduction in broadband content and thus actually getting the caption material to users on the Web. There is a companion document (a recommended practice) SMPTE RP-2052-10 which gives guidance on how to convert legacy CEA 608 into the XML format.

There is also a free overview document SMPTE 2052-0 which gives the scope of the standard and that walks through some of the use cases.

Extract from Scope
This Standard defines the SMPTE profile of W3C Timed Text Markup Language (TTML), designated SMPTE-TT, which may represent Captions or Subtitles. It identifies the features from TTML required for interoperability between display systems for the format. In order to preserve certain semantic features of the input formats, SMPTE-TT also defines some standard metadata terms to be used, and some extension features not found in TTML.&lt;ref>&lt;/ref>

Technology
Every SMPTE-TT file is also a W3C TTML file, the additions created by SMPTE-TT can be ignored by a standard TTML processor and the content will still work as intended. The additions are primarily in the metadata space and contain facilitites for transporting arbitrary binary data encoded using BASE64, image data and other meta information about the caption format.

TTML was designed by subtitling experts, Broadcasters and Web technologists, and so has most of the features required in a modern caption or subtitling facility, including:
 * Unicode support in order to present special characters(e.g. musicnotes, Asian scripts, Mathematics)
 * Metadata support to indicate for automatic processing (e.g. who is speaking)
 * Capable of positioning of captions anywhere in the picture area, multiple simultaneous captions,
 * Capable of automatic flow for roll-up type scenarios
 * Rich font style support including bold, italic and underline text support.

&lt;img alt="Production workflow with SMPTE TT" src=""> &lt;description of workflow>

The additional functionality of SMPTE-TT was added to facilitate the conversion from pre-existing formats, for archive interchange and redistribution.

Examples
This simple example shows the basic structure of a TTML file, it has four captions, that will be presented in a rollup form. It is a legal SMPTE-TT file, but does not contain any of the SMPTE-TT extensions.

&lt;tt xmlns="http://www.w3.org/ns/ttml" xml:lang="en"> &lt;body> &lt;div> &lt;p begin="00:00:00.00" dur="4s">[Example SMPTE-TT file]&lt;/p> &lt;p begin="00:00:01.32" dur="4s">Hello Wikipedia&lt;/p> &lt;p begin="00:00:02.31" dur="4s">This is a basic Example&lt;/p> &lt;p begin="00:00:03.41" dur="4s">of rollup style captioning&lt;/p> &lt;/div> &lt;/body> &lt;/tt>

Example of image captions
In this following example, more features of TTML are used, including the smpte:backgroundImage attribute which causes a referenced image to be used as the background for a div element. The text it still added to the region, so that it can be used for example for spoken captioning, but it is drawn transparently.

Additionally in this example we can see how regions on the screen can be targetted by individual captions, and also be moved around during the presentation. These features can be used to model CEA 608 presentation features.

&lt;tt xmlns:smpte="http://www.smpte-ra.org/schemas/2052-1/2010/smpte-tt" xmlns="http://www.w3.org/ns/ttml" xmlns:ttm="http://www.w3.org/ns/ttml#metadata" xmlns:tts='http://www.w3.org/ns/ttml#styling' xml:lang="en"> &lt;head> &lt;layout> &lt;region xml:id="imageRegion" tts:color="transparent" tts:origin="0% 0%" tts:extent="100% 100%" > &lt;set begin="0.19305s" end="0.21581s" tts:origin="0px 2px" tts:extent="4px 8px" /> &lt;set begin="5.89876s" end="8.09467s" tts:origin="230px 50px" tts:extent="243px 58px" /> &lt;set begin="8.20106s" end="10.1922s" tts:origin="202px 50px" tts:extent="302px 64px" /> &lt;set begin="10.3032s" end="12.2943s" tts:origin="180px 402px" tts:extent="341px 32px" /> &lt;/region> &lt;/layout> &lt;/head> &lt;body> &lt;div region="imageRegion"> &lt;div begin="0.19305s" end="0.21581s" smpte:backgroundImage="Subtitles_EN/SPU0.png"> &lt;p>[Example SMPTE-TT file]&lt;/p> &lt;/div> &lt;div begin="5.89876s" end="8.09467s" smpte:backgroundImage="Subtitles_EN/SPU1.png"> &lt;p>Hello Wikipedia&lt;/p> &lt;/div> &lt;div begin="8.20106s" end="10.1922s" smpte:backgroundImage="Subtitles_EN/SPU2.png"> &lt;p>This is a basic Example&lt;/p> &lt;/div> &lt;div begin="10.3032s" end="12.2943s" smpte:backgroundImage="Subtitles_EN/SPU3.png" > &lt;p>of pop on style captioning with preformatted background images&lt;/p> &lt;/div> &lt;/div> &lt;/body> &lt;/tt>

Player software

 * Adobe CS4
 * HTML5 DFXP Player prototype
 * CC for Flash component
 * JW FLV Media Player
 * NCAM ccPlayer
 * Microsoft Silverlight Media Framework
 * Microsoft Expression Encoder 4 Silverlight Player Templates

Authoring software

 * Annotation Edit
 * Caption Colorado
 * Caption Wrap
 * Captionate
 * CaptionSync
 * CPC
 * Screen Subtitling
 * SoftelSwift
 * Subtitle-horse
 * FAB Broadcast (only Export)

Endorsements
The Coalition of Organizations for Accessible Technology(COAT) expects this work to go a long way to ensure more carriage of captions on Internet content and will facilitate implementation of the requirements in the 21st Century Communications & Video Accessibility Act of 2010.