TTML Simple Delivery Profile for Closed Captions (US)

Table of Contents

• 1. Introduction
• 2. Terms, Definitions, and Conventions
• 3. Conformance
• 4. Structural Constraints
  • 4.1 Use of Constrained TTML Feature #content
  • 4.2 Use of Constrained TTML Feature #profile
• 5. Style Constraints
  • 5.1 Use of Constrained TTML Feature #backgroundColor-*
  • 5.2 Use of Constrained TTML Feature #color
  • 5.3 Use of Constrained TTML Feature #extent-region
    • 5.3.1 Examples
  • 5.4 Use of Constrained TTML Feature #fontFamily-generic
  • 5.5 Use of Constrained TTML Feature #fontSize
  • 5.6 Use of Constrained TTML Feature #styling-*
• 6. Layout Constraints
  • 6.1 Use of Constrained TTML Feature #layout
• 7. Timing Constraints
  • 7.1 Use of Constrained TTML Feature #timing
  • 7.2 Use of Constrained TTML Feature #animation
• 8. Other Constraints
  • 8.1 Encoding Constraints
  • 8.2 Ease of Use Constraints
• 9. Features in TTML 1.0 Used in This Profile
• 10. Error handling
• A. Future Needs for TTML next for Simple Delivery
  • A.1 Values for font family support
  • A.2 Support for character edge features
  • A.3 Specify rendering model that accounts for drawing performance
• B. Mapping of US Government Requirements to Constrained Profile Features
• C. Code points
• D. Color values
• E. Acknowledgements
• F. References
  • F.1 Normative references
  • F.2 Informative references

1. Introduction

TTML 1.0 [TTML10] provides many features to satisfy captioning and subtitling requirements, not all of which are intended for end user display. Requirements have been identified by key video and content communities to define an interoperable delivery profile using the core features specifically designed for online presentation of TTML. Such a profile allows the community of TTML users to construct constrained presentation engines for TTML. This document defines the behavior expected of a TTML content player using the presentation processor constraints for such an online delivery profile.

The Simple Online Delivery profile is focused on streamlined delivery of closed captions on the Internet. This interoperability profile supports core TTML features to deliver legacy formats such as [CEA608] and [CEA708] content, and, as such, is targeted primarily for use in US markets.

The Simple Delivery Profile for Closed Captions focuses on interoperability using [TTML10] to support delivery of closed captions for video content. Other profiles based on [TTML10] may target other types of subtitles such as on-screen text or graphics. This interoperability profile is a proper subset of [TTML10] intended to support features required for US Government closed captioning requirements for online presentation.

2. Terms, Definitions, and Conventions

The terms and definitions in [TTML10] serve as the basis for this interoperability profile. The following terms supplant those found in [TTML10].

When this document refers to a TTML element type and no namespace prefix is specified, then the tt namespace prefix is implied. This prefix and other explicit namespace prefixes used herein correspond to those TTML namespaces defined in [TTML10] Section 5.1.

3. Conformance

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words must, must not, required, should, should not, recommended, may, and optional in this specification are to be interpreted as described in [RFC2119].

This profile defines (1) constraints on documents and (2) minimum requirements for a TTML presentation processor capable of presenting such constrained documents.

A document conforms to this profile if it:

1. contains all elements and attributes required by this profile;
2. does not contain or employ elements and attributes that are prohibited by this profile; and
3. satisfies all other semantic constraints defined by this profile.

A conformant document is said to be strictly conformant if it does not contain any feature that is not explicitly specified as included in this profile.

A TTML presentation processor conforms to this profile if it:

1. implements support for the profile definition specified in Features in TTML 1.0 Used in This Profile; and
2. implements support for all other semantics explicitly defined by this profile.

The semantics defined in [TTML10] apply unless otherwise constrained in this profile.

Claims of document conformance must make use of the following profile URI, identified with the indicated profile name:

Conformance to this profile does not preclude:

1. use of other features defined in [TTML10], in which case such behavior is not defined here; or
2. use of other profiles that may implement the features in this profile.

5. Style Constraints

<region xml:id="r1" tts:backgroundColor="#00000000"/>
...
<p region="r1" tts:backgroundColor="#1049edff">
  Twinkle, twinkle, little bat!<br/>
  How <span tts:backgroundColor="#ed1078ff">I wonder</span> where you're at!
</p>

<?xml version="1.0" encoding="utf-8"?>
<tt xml:lang="en-us" xmlns="http://www.w3.org/ns/ttml" 
    xmlns:s="http://www.w3.org/ns/ttml#styling" 
    xmlns:p="http://www.w3.org/ns/ttml#parameter">
  <head>
    <p:profile use="http://www.w3.org/ns/ttml/profile/sdp-us"/>
    <styling>
      <!-- A typical transparent region with centered text that has an outline -->
      <style xml:id="bottomMidStyle" s:textAlign="center" s:textOutline="#000000ff 5%" s:backgroundColor="#00000000" 
                s:color="#ffffffff" s:origin='20% 58%' s:extent='60% 18%'/>
    </styling>
    <layout>
      <!-- typical 'Pop-up' type region -->
      <region xml:id="bottomMid" style="bottomMidStyle" />
    </layout>
  </head>
  <body>
    <div style="defaultFont">
      <p region="bottomMid" begin='00:00:00.101' end='00:00:03.000'> This is a Pop-up caption. </p>
    </div>
  </body>
</tt>

<style xml:id="bottomMidStyle" s:textAlign="center" s:textOutline="black 1px" s:backgroundColor="transparent" 
       s:color="#ffffffff" s:origin='20% 58%' s:extent='60% 18%'/>
<style xml:id="topMidStyle" s:textAlign="center" s:textOutline="black 1px" s:backgroundColor="transparent" 
       s:color="#ffffffff" s:origin='20% 10%' s:extent='60% 18%'/>

<?xml version="1.0" encoding="utf-8"?>
<tt xml:lang="en-us" xmlns="http://www.w3.org/ns/ttml"
    xmlns:s="http://www.w3.org/ns/ttml#styling"
    xmlns:p="http://www.w3.org/ns/ttml#parameter">
  <head>
    <p:profile use="http://www.w3.org/ns/ttml/profile/sdp-us"/>
    <styling>
      <style xml:id="s1" s:display="none" s:extent='40% 18%'/>
    </styling>
    <layout>
      <region xml:id="r1" style="s1">
        <set begin='00:00:10.000' end='00:00:10.330' s:display='auto'/>
        <set begin='00:00:10.000' end='00:00:10.330' s:origin='10% 10%'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:display='auto'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:origin='10% 10%'/>
      </region>
      <region xml:id="r2" style="s1">
        <set begin='00:00:10.330' end='00:00:10.670' s:display='auto'/>
        <set begin='00:00:10.330' end='00:00:10.670' s:origin='50% 10%'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:display='auto'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:origin='50% 10%'/>
      </region>
      <region xml:id="r3" style="s1">
        <set begin='00:00:10.670' end='00:00:11.000' s:display='auto'/>
        <set begin='00:00:10.670' end='00:00:11.000' s:origin='10% 78%'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:display='auto'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:origin='10% 78%'/>
      </region>
      <region xml:id="r4" style="s1">
        <set begin='00:00:11.000' end='00:00:11.330' s:display='auto'/>
        <set begin='00:00:11.000' end='00:00:11.330' s:origin='50% 78%'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:display='auto'/>
        <set begin='00:00:11.670' end='00:00:12.000' s:origin='50% 78%'/>
      </region>
    </layout>
  </head>
  <body>
    <div>
      <!--four speakers count off, and then all call 'Jump' together -->
      <p begin='00:00:10.000' end='00:00:10.330' region="r1" >One</p>
      <p begin='00:00:10.330' end='00:00:10.670' region="r2" >Two</p>
      <p begin='00:00:10.670' end='00:00:11.000' region="r3">Three</p>
      <p begin='00:00:11.000' end='00:00:11.330' region="r4" >Four</p>
      <p begin='00:00:11.670' end='00:00:12.000' region="r1" >Jump!</p>
      <p begin='00:00:11.670' end='00:00:12.000' region="r2" >Jump!</p>
      <p begin='00:00:11.670' end='00:00:12.000' region="r3">Jump!</p>
      <p begin='00:00:11.670' end='00:00:12.000' region="r4" >Jump!</p>
    </div>
  </body>
</tt>

6. Layout Constraints

<p>I always get the fuzzy end<br/>of the lollipop.</p>

7. Timing Constraints

<p begin='00:00:01.000' end='00:00:11.123' region="r1" >Test</p>

<tt p:frameRate='30' p:frameRateMultiplier='1000 1001' ...>
...
<p begin='00:00:01:00' end='00:00:11:22' region="r1" >Test</p>

8. Other Constraints

9. Features in TTML 1.0 Used in This Profile

The following TTML profile definition formally defines the SDP US profile, designated by the profile designator http://www.w3.org/ns/ttml/profile/sdp-us.

<?xml version="1.0" encoding="utf-8"?>
<profile xmlns="http://www.w3.org/ns/ttml#parameter">
  <features xml:base="http://www.w3.org/ns/ttml/feature/">
    <!-- required (mandatory) feature support -->
    <feature value="required">#animation</feature>
    <feature value="required">#backgroundColor-block</feature>
    <feature value="required">#backgroundColor-inline</feature>
    <feature value="required">#color</feature>
    <feature value="required">#content</feature>
    <feature value="required">#core</feature>
    <feature value="required">#display-region</feature>
    <feature value="required">#displayAlign</feature>
    <feature value="required">#extent-region</feature>
    <feature value="required">#fontFamily-generic</feature>
    <feature value="required">#fontSize</feature>
    <feature value="required">#fontStyle-italic</feature>
    <feature value="required">#frameRate</feature>
    <feature value="required">#frameRateMultiplier</feature>
    <feature value="required">#layout</feature>
    <feature value="required">#length-percentage</feature>
    <feature value="required">#length-positive</feature>
    <feature value="required">#lineBreak-uax14</feature>
    <feature value="required">#presentation</feature>
    <feature value="required">#profile</feature>
    <feature value="required">#structure</feature>
    <feature value="required">#styling</feature>
    <feature value="required">#styling-inheritance-content</feature>
    <feature value="required">#styling-inheritance-region</feature>
    <feature value="required">#styling-inline</feature>
    <feature value="required">#styling-referential</feature>
    <feature value="required">#textAlign-absolute</feature>
    <feature value="required">#textDecoration-under</feature>
    <feature value="required">#textOutline-unblurred</feature>
    <feature value="required">#time-offset</feature>
    <feature value="required">#timing</feature>
    <feature value="required">#writingMode-horizontal-lr</feature>
  </features>
</profile>

10. Error handling

The semantics defined by [TTML10] Section 6.1.1 apply with regard to the presence of a reference to other standard or non-standard profiles. In particular, if an additional, non-standard profile is specified for use by a document and is not dereferencable by the presentation processor, then the document must not be further processed without an explicit override from the end user.

The semantics defined by [TTML10] Section 6.1.3 apply if some standard or non-standard feature is required, the feature is present in the document, and the presentation processor does not support that feature. In this case also, the document must not be further processed without an explicit override from the end user.

If a feature is present in a document and support for that feature is not required by the profile(s) referenced (or defined) by the document, and if the presentation processor does not support or otherwise recognize that feature, then the feature must be ignored.