RFC 2733 (rfc2733) - Page 1 of 26

An RTP Payload Format for Generic Forward Error Correction

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Network Working Group                                       J. Rosenberg
Request for Comments: 2733                                   dynamicsoft
Category: Standards Track                                 H. Schulzrinne
                                                     Columbia University
                                                           December 1999


       An RTP Payload Format for Generic Forward Error Correction


Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

   This document specifies a payload format for generic forward error
   correction of media encapsulated in RTP. It is engineered for FEC
   algorithms based on the exclusive-or (parity) operation. The payload
   format allows end systems to transmit using arbitrary block lengths
   and parity schemes. It also allows for the recovery of both the
   payload and critical RTP header fields. Since FEC is sent as a
   separate stream, it is backwards compatible with non-FEC capable
   hosts, so that receivers which do not wish to implement FEC can just
   ignore the extensions.

Table of Contents

   1     Introduction ...........................................    2
   2     Terminology ............................................    2
   3     Basic Operation ........................................    3
   4     Parity Codes ...........................................    5
   5     RTP Media Packet Structure .............................    6
   6     FEC Packet Structure ...................................    7
   6.1   RTP Header of FEC Packets ..............................    7
   6.2   FEC Header .............................................    7
   7     Protection Operation ...................................    9
   8     Recovery Procedures ....................................   10
   8.1   Reconstruction .........................................   10
   8.2   Determination of When to Recover .......................   12



Rosenberg & Schulzrinne     Standards Track
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