The audio/mpeg Media Type (RFC3003)
Original Publication Date: 2000-Nov-01
Included in the Prior Art Database: 2019-Feb-14
Internet Society Requests For Comment (RFCs)
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. [STANDARDS-TRACK]
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 (C) The Internet Society (2000). All Rights Reserved.
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: email@example.com Subject: Registration of MIME media type audio/mpeg
MIME media type name: audio
MIME subtype name: mpeg
Required parameters: none
Optional parameters: none
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 encod...