Internet DRAFT - draft-nilsson-audio-mpeg
draft-nilsson-audio-mpeg
Internet Engineering Task Force M. Nilsson
INTERNET DRAFT 27 August 2000
Document: draft-nilsson-audio-mpeg-03.txt
Expires 27 February 2001
The audio/mpeg 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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
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Abstract
The audio layers of the MPEG-1 and MPEG-2 standards are in frequent
use on the internet, but there is no uniform MIME type for these
files. The intention of this draft 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
synchronisation or in other ways not possible to decompress without
error.
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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
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.
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.
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
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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 draft.
Intended usage: COMMON
Author/Change controller: Martin Nilsson (see section 5)
3. 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)
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[RFC2119]
S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
<url:ftp://ftp.isi.edu/in-notes/rfc2119.txt>
4. 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 implmentation 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."
5. Authors Address
Martin Nilsson
Rydsv„gen 246 C. 30
S-584 34 Link÷ping
Sweden
Email: nilsson@id3.org
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