Real-Time Transport Protocol (RTP) Payload for Text Conversation Interleaved in an Audio Stream
RFC 4351
| Document | Type | RFC - Historic (January 2006; No errata) | |
|---|---|---|---|
| Authors | Paul Jones , Gunnar Hellstrom | ||
| Last updated | 2018-12-20 | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4351 (Historic) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | csp@csperkins.org, magnus.westerlund@ericsson.com | ||
Network Working Group G. Hellstrom
Request for Comments: 4351 Omnitor AB
Category: Historic P. Jones
Cisco Systems, Inc.
January 2006
Real-Time Transport Protocol (RTP) Payload for
Text Conversation Interleaved in an Audio Stream
Status of This Memo
This memo defines a Historic Document for the Internet community. It
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This memo describes how to carry real-time text conversation session
contents in RTP packets. Text conversation session contents are
specified in ITU-T Recommendation T.140.
One payload format is described for transmitting audio and text data
within a single RTP session.
This RTP payload description recommends a method to include redundant
text from already transmitted packets in order to reduce the risk of
text loss caused by packet loss.
Hellstrom & Jones Historic [Page 1]
RFC 4351 RTP Payload for Text in an Audio Stream January 2006
Table of Contents
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................4
3. Usage of RTP ....................................................4
3.1. Motivations and Rationale ..................................4
3.2. Payload Format for Transmission of audio/t140c Data ........4
3.3. The "T140block" ............................................5
3.4. Synchronization of Text with Other Media ...................5
3.5. Synchronization Considerations for the audio/t140c Format ..5
3.6. RTP Packet Header ..........................................6
4. Protection against Loss of Data .................................7
4.1. Payload Format When Using Redundancy .......................7
4.2. Using Redundancy with the audio/t140c Format ...............8
5. Recommended Procedure ...........................................8
5.1. Recommended Basic Procedure ................................8
5.2. Transmission before and after "Idle Periods" ...............9
5.3. Detection of Lost Text Packets .............................9
5.4. Compensation for Packets Out of Order .....................10
6. Parameter for Character Transmission Rate ......................10
7. Examples .......................................................11
7.1. RTP Packetization Examples for the audio/t140c Format .....11
7.2. SDP Examples ..............................................12
8. Security Considerations ........................................13
8.1. Confidentiality ...........................................13
8.2. Integrity .................................................13
8.3. Source Authentication .....................................13
9. Congestion Considerations ......................................14
10. IANA Considerations ...........................................15
10.1. Registration of MIME Media Type audio/t140c ..............15
10.2. SDP Mapping of MIME Parameters ...........................16
10.3. Offer/Answer Consideration ...............................17
11. Acknowledgements ..............................................17
12. Normative References ..........................................17
13. Informative References ........................................18
Hellstrom & Jones Historic [Page 2]
RFC 4351 RTP Payload for Text in an Audio Stream January 2006
1. Introduction
This document defines a payload type for carrying text conversation
session contents in RTP [2] packets. Text conversation session
contents are specified in ITU-T Recommendation T.140 [1]. Text
conversation is used alone or in connection to other conversational
facilities, such as video and voice, to form multimedia conversation
services. Text in multimedia conversation sessions is sent
character-by-character as soon as it is available, or with a small
delay for buffering.
The text is intended to be entered by human users from a keyboard,
handwriting recognition, voice recognition, or any other input
method. The rate of character entry is usually at a level of a few
characters per second or less. In general, only one or a few new
characters are expected to be transmitted with each packet. Small
blocks of text may be prepared by the user and pasted into the user
interface for transmission during the conversation, occasionally
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