RFC 3119 (rfc3119) - Page 1 of 19
A More Loss-Tolerant RTP Payload Format for MP3 Audio
Alternative Format: Original Text Document
Network Working Group R. Finlayson
Request for Comments: 3119 LIVE.COM
Category: Standards Track June 2001
A More Loss-Tolerant RTP Payload Format for MP3 Audio
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 (2001). All Rights Reserved.
Abstract
This document describes a RTP (Real-Time Protocol) payload format for
transporting MPEG (Moving Picture Experts Group) 1 or 2, layer III
audio (commonly known as "MP3"). This format is an alternative to
that described in RFC 2250, and performs better if there is packet
loss.
1. Introduction
While the RTP payload format defined in RFC 2250 [2] is generally
applicable to all forms of MPEG audio or video, it is sub-optimal for
MPEG 1 or 2, layer III audio (commonly known as "MP3"). The reason
for this is that an MP3 frame is not a true "Application Data Unit" -
it contains a back-pointer to data in earlier frames, and so cannot
be decoded independently of these earlier frames. Because RFC 2250
defines that packet boundaries coincide with frame boundaries, it
handles packet loss inefficiently when carrying MP3 data. The loss
of an MP3 frame will render some data in previous (or future) frames
useless, even if they are received without loss.
In this document we define an alternative RTP payload format for MP3
audio. This format uses a data-preserving rearrangement of the
original MPEG frames, so that packet boundaries now coincide with
true MP3 "Application Data Units", which can also (optionally) be
rearranged in an interleaving pattern. This new format is therefore
more data-efficient than RFC 2250 in the face of packet loss.
Finlayson Standards Track