Requirements for an Internet Audio Codec
RFC 6366

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Internet Engineering Task Force (IETF)                          J. Valin
Request for Comments: 6366                                       Mozilla
Category: Informational                                           K. Vos
ISSN: 2070-1721                                 Skype Technologies, S.A.
                                                             August 2011

                Requirements for an Internet Audio Codec

Abstract

   This document provides specific requirements for an Internet audio
   codec.  These requirements address quality, sampling rate, bit-rate,
   and packet-loss robustness, as well as other desirable properties.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6366.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Valin & Vos                   Informational                     [Page 1]
RFC 6366                Audio Codec Requirements             August 2011

Table of Contents

   1. Introduction ....................................................2
   2. Definitions .....................................................3
   3. Applications ....................................................3
      3.1. Point-to-Point Calls .......................................3
      3.2. Conferencing ...............................................4
      3.3. Telepresence ...............................................5
      3.4. Teleoperation and Remote Software Services .................5
      3.5. In-Game Voice Chat .........................................5
      3.6. Live Distributed Music Performances / Internet
           Music Lessons ..............................................6
      3.7. Delay-Tolerant Networking or Push-to-Talk Services .........6
      3.8. Other Applications .........................................7
   4. Constraints Imposed by the Internet on the Codec ................7
   5. Detailed Basic Requirements .....................................8
      5.1. Operating Space ............................................9
      5.2. Quality and Bit-Rate .......................................9
      5.3. Packet-Loss Robustness ....................................10
      5.4. Computational Resources ...................................10
   6. Additional Considerations ......................................12
      6.1. Low-Complexity Audio Mixing ...............................12
      6.2. Encoder Side Potential for Improvement ....................12
      6.3. Layered Bit-Stream ........................................13
      6.4. Partial Redundancy ........................................13
      6.5. Stereo Support ............................................13
      6.6. Bit Error Robustness ......................................13
      6.7. Time Stretching and Shortening ............................14
      6.8. Input Robustness ..........................................14
      6.9. Support of Audio Forensics ................................14
      6.10. Legacy Compatibility .....................................14
   7. Security Considerations ........................................14
   8. Acknowledgments ................................................15
   9. Informative References .........................................15

1.  Introduction

   This document provides requirements for an audio codec designed
   specifically for use over the Internet.  The requirements attempt to
   address the needs of the most common Internet interactive audio
   transmission applications and ensure good quality when operating in
   conditions that are typical for the Internet.  These requirements
   also address the quality, sampling rate, delay, bit-rate, and packet-
   loss robustness.  Other desirable codec properties are considered as