Browse Prior Art Database

Options for Repair of Streaming Media (RFC2354)

IP.com Disclosure Number: IPCOM000002924D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 10 page(s) / 27K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

C. Perkins: AUTHOR [+2]

Abstract

This document summarizes a range of possible techniques for the repair of continuous media streams subject to packet loss. The techniques discussed include redundant transmission, retransmission, interleaving and forward error correction. The range of applicability of these techniques is noted, together with the protocol requirements and dependencies.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 11% of the total text.

Network Working Group C. Perkins

Request for Comments: 2354 O. Hodson

Category: Informational University College London

June 1998

Options for Repair of Streaming Media

Status of this Memo

This memo provides information for the Internet community. This memo

does not specify an Internet standard of any kind. Distribution of

this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.

Abstract

This document summarizes a range of possible techniques for the

repair of continuous media streams subject to packet loss. The

techniques discussed include redundant transmission, retransmission,

interleaving and forward error correction. The range of

applicability of these techniques is noted, together with the

protocol requirements and dependencies.

1 Introduction

A number of applications have emerged which use RTP/UDP transport to

deliver continuous media streams. Due to the unreliable nature of

UDP packet delivery, the quality of the received stream will be

adversely affected by packet loss. A number of techniques exist by

which the effects of packet loss may be repaired. These techniques

have a wide range of applicability and require varying degrees of

protocol support. In this document, a number of such techniques are

discussed, and recommendations for their applicability made.

It should be noted that this document is introductory in nature, and

does not attempt to be comprehensive. In particular, we restrict our

discussion to repair techniques which require the involvement of the

sender of a media stream, and do not discuss possibilities for

receiver based repair.

For a more detailed survey, the reader is referred to [5].

2 Terminology and Protocol Framework

A unit is defined to be a timed interval of media data, typically

derived from the workings of the media coder. A packet comprises one

or more units, encapsulated for transmission over the network. For

example, many audio coders operate on 20ms units, which are typically

combined to produce 40ms or 80ms packets for transmission. The

framework of RTP [18] is assumed. This implies that packets have a

sequence number and timestamp. The sequence number denotes the order

in which packets are transmitted, and is used to detect losses. The

timestamp is used to determine the playout order of units. Most loss

recovery schemes rely on units being sent out of order, so an

application must use the RTP timestamp to schedule playout.

The use of RTP allows for several different media coders, with a

payload type field being used to distinguish between these at the

receiver. Some loss repair schemes send multiple copies of units, at

different times and possibly with different encodings, to increase

the proba...