Internet Engineering Task Force M. Nilsson INTERNET DRAFT 26 April 2000 Document: draft-nilsson-audio-mpeg-02.txt Expires 26 October 2000 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- Drafts. 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 http://www.ietf.org/shadow.html. 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. 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. Nilsson [Page 1]
Internet DRAFT The audio/mpeg Media Type April 2000 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: Data concatenated with the MPEG stream might contain executable code. This executable code can only be executed by a program that looks for it and is not executed by an MPEG audio decoder when it attempts to play the file. It's simply ignored. Interoperability considerations: MPEG audio has proven to be widely interoperable across computer platforms. Published specification: see [MPEG-1] and [MPEG-2] Nilsson [Page 2]
Internet DRAFT The audio/mpeg Media Type April 2000 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, "ID3v2 informal standard". <url:http://www.id3.org/id3v2-00.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) Nilsson [Page 3]
Internet DRAFT The audio/mpeg Media Type April 2000 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 Rydsvgen 246 C. 30 S-584 34 Link÷ping Sweden Email: nilsson@id3.org Nilsson Expires 26 October 2000 [Page 4]