Internet DRAFT - draft-walleij-vorbis-mediatype


Network Working Group                                         L. Walleij
Internet-Draft                                  The Ogg Vorbis Community
Expires: November 27, 2001                                  May 29, 2001

                      The audio/vorbis Media Type

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


   The Vorbis audio format aim at becoming a general patent-free
   standard for transporting psychoacoustically compressed audio content
   across computing platforms and networks.  The intention of this
   document is to define the media type audio/vorbis to refer to this
   kind of content when transported synchronously or asynchronously
   across the Internet.  For synchronous transport using the real-time
   transport protocol (RTP) with a Vorbis payload [5] as well as for
   asynchronous transport with the Ogg Bitstream Format [1] this MIME
   type should be used.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

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   document are to be interpreted as described in RFC 2119 [3].

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1. The Vorbis Bitstream Format

   The Vorbis Bitstream format has been developed as a part of a larger
   project aiming at presenting a series of multimedia content carrier
   bitstreams, which are to be freely available for the computing
   community at large, including the Internet community.  These
   multimedia bitstreams are created by software or hardware components
   known as codecs, encoder-decoders.

   Raw packets from these codecs may be used directly by transport
   mechanisms that provide their own framing and packet-seperation
   mechanisms (such as UDP datagrams).

   One such framing and content-separation mechanism is the real-time
   transport protocol (RTP) as described in [5].  In this case the MIME
   type used is audio/parityfec for the wrapping RTP stream, whereas
   this MIME type, audio/vorbis, is used to denote the Vorbis payload
   inside the RTP wrapper.

   For stream based storage (such as files) and transport (such as TCP
   streams or pipes), the Vorbis codec will typically use the Ogg
   Bitstream Format to provide framing/sync, sync recapture after error,
   landmarks during seeking, and enough information to properly seperate
   data back into packets at the original packet boundaries without
   relying on decoding to find packet boundaries.  In this case the
   audio/vorbis MIME type refers to an Ogg Bitstream [1] containing one
   channel of Vorbis audio.

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2. Registration Information


   Subject: Registration of MIME media type audio/vorbis

   MIME media type name: audio

   MIME subtype name: vorbis

   Required parameters: none

   Optional parameters: none

   Encoding Considerations:

   The Vorbis audio data is always wrapped inside an RTP or Ogg
   bitstream when transported with this MIME type, see [5] or [1].

   The Vorbis audio data is binary data, and must be encoded for non-
   binary transport; the Base64 encoding is suitable for Email, Binary
   encoding could also be used.  Further lossless compression may be
   problematic as the Vorbis data is already efficiently compressed
   using psychoacoustic algorithms with highly optimized bit-allocation.

   Security Considerations:

   Ideally, the Vorbis file can not contain security-violating code as
   the format is highly specified, see [1] and/or [2].  However, fields
   can be abused if the receiving decoder implementation has errors or
   extensions that make it possible to embed interpretative or object
   code.  The receiving decoder must therefore take these issues into
   account, and under no circumstances allow untrusted code to be

   The wrapping format, the RTP or Ogg bitstream, could potentially wrap
   any content, even executable code, so for other usage areas than
   Vorbis audio, additional security considerations must be taken.

   Vorbis files are not signed or encrypted using any applicable
   encryption schemes.  External security mechanisms must be added if
   content confidentiality and authenticity is to be achieved.

   Interoperability considerations:

   The Vorbis format has proved to be widely implementable across
   different computing platforms.  A broadly portable reference
   implementation is available under a BSD license.

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   The technology involved in Vorbis encoding and decoding is not
   patented and may be used by third parties without patent licenses or
   similar licensing issues.

   Published specification:

   See [1] and/or [2].

   Applications which use this media type:

   Any application that implements the specification will be able to
   encode or decode Vorbis files.

   Additional information:

   Magic number(s):

   For Vorbis files wrapped inside Ogg bitstream files, the first four
   bytes are 0x4f 0x67 0x67 0x53 corresponding to the string "OggS".
   The Vorbis header will then additionally contain the lowercase string
   "vorbis" (comprising the bytes 0x76 0x6f 0x72 0x62 0x69 0x73) at
   offset 0x1d, where offset 0x00 is the first byte of the file.

   File extension: .ogg

   Macintosh File Type Code(s): OggS

   Object Identifier(s) or OID(s): none

   Person & email address to contact for further information:

   Questions about this proposal should be directed to Linus Walleij
   <>.  Technical questions about the Vorbis format and
   the Ogg bitstream standard may be asked on the mailing lists for the
   Vorbis developer community.  <>

Intended usage: COMMON

   Author/Change controller:

   This document was written by Linus Walleij <>, changes
   of this document will be handled by him or a representative of the Foundation or the vorbis development community.

   The Vorbis format and the framing mechanism of the Ogg Bitstream
   Format is controlled by the Foundation and the respective
   development communities.

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3. Security Considerations

   Security considerations are discussed in the security considerations
   clause of the MIME registration in section 2.

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   [1]  The Foundation, ., "OggSquish logical and physical
        bitstream overview", June 2001,

   [2]  Coleman, M., "Vorbis Illuminated", June 2001,

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Rosenberg, J. and H. Schulzrinne, "Registration of parityfec
        MIME types", RFC 3009, November 2000.

   [5]  Moffitt, J., "RTP Payload Format for Vorbis Encoded Audio", I-D
        draft-moffitt-vorbis-rtp-00.txt, February 2001.

Author's Address

   Linus Walleij
   The Ogg Vorbis Community
   Master Olofs Vag 24
   Lund  224 66

   Phone: +46 703 193678

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