RTP Payload for TTML Timed Text
draft-ietf-payload-rtp-ttml-06

Document Type Active Internet-Draft (avtcore WG)
Last updated 2019-11-20 (latest revision 2019-11-19)
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
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Responsible AD Barry Leiba
Send notices to Roni Even <roni.even@huawei.com>
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RFC Editor RFC Editor state EDIT
A/V Transport Payloads Workgroup                             J. Sandford
Internet-Draft                          British Broadcasting Corporation
Intended status: Standards Track                        19 November 2019
Expires: 22 May 2020

                    RTP Payload for TTML Timed Text
                     draft-ietf-payload-rtp-ttml-06

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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   This Internet-Draft will expire on 22 May 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
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Sandford                   Expires 22 May 2020                  [Page 1]
Internet-Draft       RTP Payload for TTML Timed Text       November 2019

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
   5.  Payload content restrictions  . . . . . . . . . . . . . . . .   5
   6.  Payload processing requirements . . . . . . . . . . . . . . .   6
     6.1.  TTML Processor profile  . . . . . . . . . . . . . . . . .   7
       6.1.1.  Feature extension designation . . . . . . . . . . . .   7
       6.1.2.  Processor profile document  . . . . . . . . . . . . .   7
       6.1.3.  Processor profile signalling  . . . . . . . . . . . .   8
   7.  Payload Examples  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Fragmentation of TTML Documents . . . . . . . . . . . . . . .  11
   9.  Protection Against Loss of Data . . . . . . . . . . . . . . .  11
   10. Congestion Control Considerations . . . . . . . . . . . . . .  12
   11. Payload Format Parameters . . . . . . . . . . . . . . . . . .  12
     11.1.  Clock Rate . . . . . . . . . . . . . . . . . . . . . . .  12
     11.2.  SDP Considerations . . . . . . . . . . . . . . . . . . .  12
       11.2.1.  Examples . . . . . . . . . . . . . . . . . . . . . .  13
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   15. Normative References  . . . . . . . . . . . . . . . . . . . .  14
   16. Informative References  . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  RFC Editor Considerations  . . . . . . . . . . . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   TTML (Timed Text Markup Language)[TTML2] is a media type for
   describing timed text such as closed captions and 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).
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