RTP Payload for Redundant Audio Data (RFC2198)
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
C. Perkins: AUTHOR [+7]
This document describes a payload format for use with the real-time transport protocol (RTP), version 2, for encoding redundant audio data. [STANDARDS-TRACK]
Network Working Group C. Perkins Request for Comments: 2198 I. Kouvelas Category: Standards Track O. Hodson V. Hardman University College London M. Handley ISI J.C. Bolot A. Vega-Garcia S. Fosse-Parisis INRIA Sophia Antipolis September 1997
RTP Payload for Redundant Audio Data
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.
This document describes a payload format for use with the real-time transport protocol (RTP), version 2, for encoding redundant audio data. The primary motivation for the scheme described herein is the development of audio conferencing tools for use with lossy packet networks such as the Internet Mbone, although this scheme is not limited to such applications.
If multimedia conferencing is to become widely used by the Internet Mbone community, users must perceive the quality to be sufficiently good for most applications. We have identified a number of problems which impair the quality of conferences, the most significant of which is packet loss. This is a persistent problem, particularly given the increasing popularity, and therefore increasing load, of the Internet. The disruption of speech intelligibility even at low loss rates which is currently experienced may convince a whole generation of users that multimedia conferencing over the Internet is not viable. The addition of redundancy to the data stream is offered as a solution . If a packet is lost then the missing information may be reconstructed at the receiver from the redundant data that arrives in the following packet(s), provided that the average number
Perkins, et. al. Standards Track [Page 1]
RFC 2198 RTP Payload for Redundant Audio Data September 1997
of consecutively lost packets is small. Recent work [4,5] shows that packet loss patterns in the Internet are such that this scheme typically functions well.
This document describes an RTP payload format for the transmission of audio data encoded in such a redundant fashion. Section 2 presents the requirements and motivation leading to the definition of this payload format, and does not form part of the payload format definition. Sections 3 onwards define the RTP payload format for redundant audio data.
The requirements for a redundant encoding scheme under RTP are as follows:
o Packets have to carry a primary encoding and one or more redundant encodings.
o As a multitude of encodings may be used for redundant information, each block of redundant encoding has to have an encoding type identifier.
o As the use of variable size encodings is desirable, each encoded block in the packet has to have a length indicator.
o The RTP header provides a timestamp field tha...