RTP Payload for TTML Timed Text
draft-ietf-payload-rtp-ttml-03

Document Type Active Internet-Draft (avtcore WG)
Last updated 2019-10-10 (latest revision 2019-10-08)
Replaces draft-sandford-payload-rtp-ttml
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication (wg milestone: Mar 2020 - Submit RTP Payload F... )
Document shepherd Roni Even
Shepherd write-up Show (last changed 2019-09-24)
IESG IESG state IESG Evaluation
Consensus Boilerplate Yes
Telechat date On agenda of 2019-10-17 IESG telechat
Has 2 DISCUSSes. Has enough positions to pass once DISCUSS positions are resolved.
Responsible AD Barry Leiba
Send notices to Roni Even <roni.even@huawei.com>
IANA IANA review state IANA OK - No Actions Needed
A/V Transport Payloads Workgroup                             J. Sandford
Internet-Draft                          British Broadcasting Corporation
Intended status: Standards Track                         October 7, 2019
Expires: April 9, 2020

                    RTP Payload for TTML Timed Text
                     draft-ietf-payload-rtp-ttml-03

Abstract

   This memo describes a Real-time Transport Protocol (RTP) payload
   format for TTML, an XML based timed text format for live and file
   based workflows from W3C.  This payload format is specifically
   targeted at live workflows using TTML.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 9, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions, Definitions, and Abbreviations . . . . . . . . .   2
   3.  Media Format Description  . . . . . . . . . . . . . . . . . .   3
     3.1.  Relation to Other Text Payload Types  . . . . . . . . . .   3
     3.2.  TTML2 . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Payload Format  . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  RTP Header Usage  . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Payload Data  . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  TTML Profile for RTP Carriage . . . . . . . . . . . .   5
   5.  Payload Examples  . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Congestion Control Considerations . . . . . . . . . . . . . .  10
   7.  Payload Format Parameters . . . . . . . . . . . . . . . . . .  11
     7.1.  Clock Rate  . . . . . . . . . . . . . . . . . . . . . . .  11
     7.2.  Mapping to SDP  . . . . . . . . . . . . . . . . . . . . .  11
       7.2.1.  Examples  . . . . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     11.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  RFC Editor Considerations  . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   TTML (Timed Text Markup Language)[TTML2] is a media type for
   describing timed text such as closed captions (also known as
   subtitles) in television workflows or broadcasts as XML.  This
   document specifies how TTML should be mapped into an RTP stream in
   live workflows including, but not restricted to, those described in
   the television broadcast oriented EBU-TT Part 3[TECH3370]
   specification.  This document does not define a media type for TTML
   but makes use of the existing application/ttml+xml media type
   [TTML-MTPR].

2.  Conventions, Definitions, and Abbreviations

   Unless otherwise stated, the term "document" refers to the TTML
   document being transmitted in the payload of the RTP packet(s).

   The term "word" refers to byte aligned or 32-bit aligned words of
   data in a computing sense and not to refer to linguistic words that
   might appear in the transported text.

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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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