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Internet Wideband Audio Codec

Document Charter Internet Wideband Audio Codec WG (codec)
Title Internet Wideband Audio Codec
Last updated 2010-01-26
State Approved
WG State Concluded
IESG Responsible AD Ben Campbell
Charter edit AD (None)
Send notices to (None)

Problem Statement
  According to reports from developers of Internet audio applications and
  operators of Internet audio services, there are no standardized,
  high-quality audio codecs that meet all of the following three
  1. Are optimized for use in interactive Internet applications.
  2. Are published by a recognized standards development organization
  (SDO) and therefore subject to clear change control.
  3. Can be widely implemented and easily distributed among application
  developers, service operators, and end users.
  There exist codecs that provide high quality encoding of audio
  information, but that are not optimized for the actual conditions of the
  Internet; according to reports, this mismatch between design and
  deployment has hindered adoption of such codecs in interactive Internet
  There exist codecs that can be widely implemented and easily
  distributed, but that are not standardized through any SDO; according to
  reports, this lack of standardization and clear change control has
  hindered adoption of such codecs in interactive Internet applications.
  There exist codecs that are standardized, but that cannot be widely
  implemented and easily distributed; according to reports, the presence
  of various usage restrictions (e.g., in the form of requirements to pay
  royalty fees, obtain a license, enter into a business agreement, or meet
  other special conditions imposed by a patent holder) has hindered
  adoptions of such codecs in interactive Internet applications.
  According to application developers and service operators, an audio
   codec that meets all three of these would: (1) enable protocol
   designers to more easily specify a mandatory-to-implement codec in
   their protocols and thus improve interoperability; (2) enable
   developers to more easily easily build innovative, interactive
   applications for the Internet; (3) enable service operators to more
   easily deploy affordable, high-quality audio services on the Internet;
   and (4) enable end users of Internet applications and services to enjoy
   an improved user experience.
  The goal of this working group is to ensure the existence of a single
  high-quality audio codec that is optimized for use over the Internet and
  that can be widely implemented and easily distributed among application
  developers, service operators, and end users.  At present it appears
  that ensuring the existence of such a codec will require a development
  effort within the working group, however if a candidate codec is
  presented that achieves the goal then the working group should seriously
  consider stopping its development work.
  The core technical considerations for such a codec include, but
  are not necessarily limited to, the following:
  1. Designing for use in interactive applications (examples include, but
  are not limited to, point-to-point voice calls, multi-party voice
  conferencing, telepresence, teleoperation, in-game voice chat, and live
  music performance)
  2. Addressing the real transport conditions of the Internet as
  identified and prioritized by the working group
  3. Ensuring interoperability and clean integration with the Real-time
  Transport Protocol (RTP), including secure transport via SRTP
  4. Ensuring interoperability with Internet signaling technologies such
  as Session Initiation Protocol (SIP), Session Description Protocol
  (SDP), and Extensible Messaging and Presence Protocol (XMPP); however,
  the result should not depend on the details of any particular signaling
  Optimizing for very low bit rates (typically below 2.4 kbps) and for
  non-interactive audio is out of scope because such work might
  necessitate specialized optimizations.
  Although a codec produced by this working group or another standards
  organization might be used as a mandatory-to-implement technology by
  designers of particular Internet protocols, it is explicitly not a goal
  of the working group to produce or select a codec that will be mandated
  for use across the entire IETF or Internet community nor would their be
  any expectation that this would be the only mandatory-to-implement
  Based on the working group's analysis of the design space, the working
  group might determine that it needs to produce more than one codec, or a
  codec with multiple modes; however, it is not the goal of working group
  to produce more than one codec, and to reduce confusion in the
  marketplace the working group shall endeavor to produce as few codecs as
  In completing its work, the working group should collaborate with other
  IETF working groups to complete particular tasks.  These might include,
  but would not be limited to, the following:
  - Within the AVT WG, define the codec's payload format for use with the
    Real-time Transport Protocol (RTP).
  - Collaborate with working groups in the Transport Area to identify
    important aspects of packet transmission over the Internet.
  - Collaborate with working groups in the Transport Area to understand
    the degree of rate adaptation desirable, and to reflect that
    understanding in the design of a codec that can adjust its
    transmission in a way that minimizes disruption to the audio.
  - Collaborate with working groups in the RAI Area to ensure that
    information about and negotiation of the codec can be easily
    represented at the signaling layer.
  In accordance with the liaison agreement in place, the working group
  will continue to coordinate with the ITU-T (Study group 16), with the
  intent of submitting the completed codec RFC for co-publication by the
  ITU-T if the ITU-T finds that appropriate. The working group will
  communicate a detailed description of the requirements and goals to
  other SDOs including the ITU-T, 3GPP, and MPEG to help determine if
  existing codecs meet the requirements and goals. Information about
  codecs being standardized will be available to other SDOs in the form of
  internet drafts and the working group welcomes technical feedback from
  other SDOs and experts from other organizations.
  Suggested Codec Standardization Guidelines and Requirements for
  achieving the foregoing objectives are provisionally outlined in
  draft-valin-codec-guidelines and draft-valin-codec-requirements
  respectively; these documents will form the starting point for working
  toward consensus and, if accepted as work items of the working group,
  will be refined by the working group in accordance with the usual IETF
  A codec that can be widely implemented and easily distributed among
  application developers, service operators, and end users is preferred.
  Many existing codecs that might fulfill some or most of the technical
  attributes listed above are encumbered in various ways.  For example,
  patent holders might require that those wishing to implement the codec
  in software, deploy the codec in a service, or distribute the codec in
  software or hardware need to request a license, enter into a business
  agreement, pay licensing fees or royalties, or attempt to adhere to
  other special conditions or restrictions.
  Because such encumbrances have made it difficult to widely implement and
  easily distribute high-quality audio codecs across the entire Internet
  community, the working group prefers unencumbered technologies in a way
  that is consistent with BCP 78 and BCP 79.  In particular, the working
  group shall heed the preference stated in BCP 79: "In general, IETF
  working groups prefer technologies with no known IPR claims or, for
  technologies with claims against them, an offer of royalty-free
  licensing."  Although this preference cannot guarantee that the working
  group will produce an unencumbered codec, the working group shall follow
  BCP 79, and adhere to the spirit of BCP 79. The working group cannot
  explicitly rule out the possibility of adopting encumbered technologies;
  however, the working group will try to avoid encumbered technologies
  that require royalties or other encumbrances that would prevent such
  technologies from being easy to redistribute and use.
  1. A set of Codec Standardization Guidelines that define the work
  processes of the working group. This document shall be Informational.
  2. A set of technical Requirements. This document shall be
  3. Specification of a codec that meets the agreed-upon requirements, in
  the form of an Internet-Draft that defines the codec algorithm along
  with source code for a reference implementation.  The text description
  of the codec shall indicate which components of the encoder and decoder
  are mandatory, recommended, and optional.  It is envisioned that this
  document shall be a Proposed Standard document.