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rfc:rfc3003

Network Working Group M. Nilsson Request for Comments: 3003 November 2000 Category: Standards Track

                     The audio/mpeg Media Type

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 (2000).  All Rights Reserved.

Abstract

 The audio layers of the MPEG-1 and MPEG-2 standards are in frequent
 use on the internet, but there is no uniform Multipurpose Internet
 Mail Extension (MIME) type for these files.  The intention of this
 document is to define the media type audio/mpeg to refer to this kind
 of contents.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

1. MPEG audio

 The audio compression defined as layer I, layer II and layer III in
 the MPEG-1 [MPEG-1] and MPEG-2 [MPEG-2] standards is a popular method
 of compressing audio with a low quality loss.  The compressed audio
 is split into several small data frames, each containing a frame
 header and compressed audio data.
 The mime type audio/mpeg defines a elementary byte stream containing
 MPEG frames according to [MPEG-1] and [MPEG-2], possibly interspersed
 with non MPEG data.  Non MPEG data is data without MPEG
 synchronization or in other ways not possible to decompress without
 error.
 Typically MPEG audio meta data is concatenated with the MPEG stream,
 e.g., the meta data format ID3 puts a 128 byte data block in the end
 of the stream while ID3v2 [ID3V2] prepends a data block of variable

Nilsson Standards Track [Page 1] RFC 3003 The audio/mpeg Media Type November 2000

 size to the stream.
 NOTE: MPEG audio was not designed as a file format but as a format
 for transmitting audio streams.  As such, it does not have any well
 defined way of including meta data along with audio information.
 Some products embed meta data using zero amplitude frames or
 disguised as transmission errors.  Others embed the MPEG data in WAV
 format.
 NOTE: The audio/MPS mime type is in use in addition to the
 audio/mpeg.  The MPA [RFC 1890] sub-type refers to MPEG audio when it
 is segmented and send as a Realtime Transport Protocol (RTP) payload.

2. Registration Information

 To: ietf-types@iana.org Subject: Registration of MIME media type
 audio/mpeg
 MIME media type name: audio
 MIME subtype name: mpeg
 Required parameters: none
 Optional parameters: none
 Encoding considerations:
     For use over internet it is assumed that lower layers take care
     of transmission errors, so audio/mpeg data MAY include MPEG
     frames generated without the optional cyclic redundancy checks
     (CRC) for improved audio quality.
     The MPEG audio data is binary data, and must be encoded for
     non-binary transport; the Base64 encoding is suitable for Email.
     Note that the MPEG audio data does not compress easily using
     lossless compression.
 Security considerations:
      MPEG is a tagged data format, and some tags are available for
      private use.  As such, arbitrary material could potentially
      be transferred in the MPEG stream, including executable content.
      Tagged data containing executable content SHOULD never be sent
      and MUST not be executed if it is received.

Nilsson Standards Track [Page 2] RFC 3003 The audio/mpeg Media Type November 2000

                              NOTE
          The requirement that such content not be executed on receipt
          is especially important since situations exist where content
          will be generated independently and therefore could contain
          executable content that the sender is unaware of.
      Audio/mpeg objects are not signed or encrypted internally.
      External security mechanisms must be employed to ensure content
      confidentiality
 Interoperability considerations:
     MPEG audio has proven to be widely interoperable across computer
     platforms.
 Published specification: see [MPEG-1] and [MPEG-2]
 Applications which use this media type:
     MPEG audio is device-, platform- and vendor-neutral and is
     supported by a wide range of encoders and decoders (players).
 Additional information:
     Magic number(s): none
     File extension(s): .mp1, .mp2, .mp3
     Macintosh File Type Code(s): MPEG
     Object Identifier(s) or OID(s): none
 Person & email address to contact for further information:
     The author of this document.
 Intended usage: COMMON
 Author/Change controller: Martin Nilsson (see section 5)
 3.  Security Considerations
 Security considerations are discussed in the security considerations
 clause of the MIME registration in section 2.

Nilsson Standards Track [Page 3] RFC 3003 The audio/mpeg Media Type November 2000

4. References

 [ID3v2]
   Martin Nilsson, "ID3 tag version 2.3.0".
   <url:http://www.id3.org/id3v2.3.0.txt>
 [MPEG-1]
   ISO/IEC 11172-3:1993.
   Coding of moving pictures and associated audio for digital storage
   media at up to about 1,5 Mbit/s, Part 3: Audio.
   Technical committee / subcommittee: JTC 1 / SC 29
 [MPEG-2]
   ISO/IEC 13818-3:1995
   Generic coding of moving pictures and associated audio information,
   Part 3: Audio.
   Technical committee / subcommittee: JTC 1 / SC 29
   and
   ISO/IEC DIS 13818-3
   Generic coding of moving pictures and associated audio information,
   Part 3: Audio (Revision of ISO/IEC 13818-3:1995)
 [RFC2119]
   Bradner, S., "Key words for use in RFCs to Indicate Requirement
   Levels", BCP 14, RFC 2119, March 1997.

5. Author's Address

 Martin Nilsson
 Rydsvagen 246 C. 30
 S-584 34 Linkoping
 Sweden
 EMail: nilsson@id3.org

Nilsson Standards Track [Page 4] RFC 3003 The audio/mpeg Media Type November 2000

6. Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Nilsson Standards Track [Page 5]

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