What is TTML2?

Timed Text Markup Language 2 (TTML2) is an XML-based language designed for the representation of timed text media, such as subtitles and captions. It serves as a standardized format for the interchange, authoring, and distribution of timed text content across various platforms and systems.

TTML2 is intended for:

  • Interchange: Facilitating the exchange of timed text information among different authoring systems.
  • Transcoding: Converting timed text content into various legacy distribution formats used in subtitling and captioning.
  • Distribution: Serving as a distribution format itself, for example, by referencing TTML content from a <track> element in an HTML5 document or a <text> or <textstream> media element in a SMIL 3.0 document.

System Model

TTML2 operates within a system model that includes authoring, transcoding, distribution, and presentation processes. It defines two classes of processors:

  1. Transformation Processors: Used in authoring systems and validation processors.
  2. Presentation Processors: Used in transcoding systems and rendering processors.

These processors can implement mappings to TTML Intermediate Documents, enabling integration with various media formats and technologies .

Document Structure

A typical TTML2 document consists of:

  • <tt>: The root element.

    • <head>: Contains metadata, styling, and layout information.

      • <metadata>: Includes document-level metadata such as title and copyright.
      • <styling>: Defines style specifications.
      • <layout>: Specifies layout regions.

    • <body>: Contains the timed text content, referencing styles and layouts.

e.g.

<tt xml:lang="" xmlns="http://www.w3.org/ns/ttml">
  <head>
    <metadata/>
    <styling/>
    <layout/>
  </head>
  <body/>
</tt>

Example:

Here’s a simple example of a TTML2 file:

<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml"
    xmlns:tts="http://www.w3.org/ns/ttml#styling"
    xml:lang="en">
  <head>
    <styling>
      <style xml:id="s1" tts:fontSize="16px" tts:color="white" tts:backgroundColor="black"/>
    </styling>
    <layout>
      <region xml:id="bottom" tts:origin="10% 80%" tts:extent="80% 10%"/>
    </layout>
  </head>
  <body region="bottom">
    <div>
      <p begin="00:00:01.000" end="00:00:04.000" style="s1">
        Hello, this is an example of TTML2 subtitles.
      </p>
      <p begin="00:00:05.000" end="00:00:08.000" style="s1">
        These captions are timed and styled.
      </p>
    </div>
  </body>
</tt>
  • <p begin="..." end="...">: Shows the subtitle text with timing.
  • <style> and <region>: Define how and where the text appears.
  • <tt>: Root element of the TTML2 document.

Changes from TTML1

TTML2 introduces several enhancements over TTML1, including:

  • Extended Features: Support for East Asian languages, stereoscopic 3D, and detailed mapping to HTML and CSS.
  • Improved Modularity: Better organization and separation of concerns within the specification.
  • Updated Syntax: Refinements to the language syntax for clarity and consistency.

A detailed summary of changes from TTML1 to TTML2 is available in the TTML2 Change Summary .

Adoption and Industry Support

TTML2 has been adopted and supported by various organizations and standards bodies, including:

  • Netflix
  • Microsoft
  • BBC
  • Apple
  • MovieLabs
  • European Broadcasting Union (EBU)

These contributors have played significant roles in the development and implementation of TTML2 .

How to open TTML2 file?

You can open and view a TTML2 file using different tools, depending on whether you want to read the text, edit the content, or display it as subtitles. TTML2 files are XML-based, so they can be opened in any text or XML editor, but to play or test them as subtitles, you need compatible tools.

To View or Edit

Use any text editor:

  • Windows: Notepad or Notepad++
  • Mac/Linux: TextEdit or VS Code

Just right-click the file → Open with → choose your editor.

To Play as Subtitles (with video)

TTML2 is not supported by most media players directly. You need to convert it to SRT or WebVTT using tools like:

  • Subtitle Edit (free app for Windows)

To Use on a Website

Use it in a <video> tag like this:

<track src="captions.ttml" kind="subtitles" label="English" srclang="en">

Note: Most browsers don’t support TTML directly. Convert to WebVTT for better compatibility.

Reference

For an in-depth understanding and technical details, you can refer to the full TTML2 specification: