Registration of Media Type audio/mobile-xmf
Register a MIME type for compact mobile music files.
Kosonen, T. and T. White, "Registration of Media Type audio/mobile-xmf", RFC 4723, DOI 10.17487/RFC4723, December 2006, <https://www.rfc-editor.org/info/rfc4723>.
@misc{rfc4723,
series = {Request for Comments},
number = 4723,
howpublished = {RFC 4723},
publisher = {RFC Editor},
doi = {10.17487/RFC4723},
url = {https://www.rfc-editor.org/info/rfc4723},
author = {T. Kosonen and T. White},
title = {{Registration of Media Type audio/mobile-xmf}},
pagetotal = 8,
year = 2006,
month = dec,
} RFC text
Contents
Network Working Group T. Kosonen
Request for Comments: 4723 Nokia
Category: Informational T. White
MMA
December 2006
Registration of Media Type audio/mobile-xmf
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2006).
Abstract
The MIDI Manufacturers Association (MMA) and the Association of
Musical Electronics Industry (AMEI) have produced the Mobile XMF
standard, which was developed particularly for mobile MIDI
applications. Mobile XMF is a very compact media type providing
high-quality synthetic audio content for music downloading and
messaging applications that require MIME registration. This document
registers the media type audio/mobile-xmf.
1. Introduction
MIDI content is used commonly in the Internet. Typically, MIDI data
is stored in the Standard MIDI File (SMF) format [8]. This MIME type
registration uses the Mobile XMF file format for the encapsulation of
SP-MIDI [3,4] and Mobile DLS (Downloadable Sounds) [2] data.
The MIDI Manufacturers Association (MMA) and the Association of
Musical Electronics Industry (AMEI) have produced the Mobile XMF
standard [1], which was developed particularly for mobile MIDI [7]
applications.
2. Registration of audio/mobile-xmf
Type name: audio
Subtype name: mobile-xmf
Required parameters: none
Optional parameters:
revision: Mobile XMF file type revision ID
revision is the Mobile XMF file type revision ID number from
the XmfFileTypeRevisionID field of the XMF Meta File format
2.00. revision is encoded in hex in US-ASCII.
prl: Playback resource list
prl contains the playback resources included in all Content
Description MetaDataItems of the Mobile XMF file. prl contains
two-digit hexadecimal numbers representing data bytes from the
Content Description Meta Data. Each resource is listed exactly
once. A playback resource contains two parts: a prefix and
data. prl is a sequence of two-digit hexadecimal numbers
encoded in US-ASCII. Thus, prl has an even number of
hexadecimal digits.
Example: If the file includes Playback Resource Lists such as
[00h 01h 00h 02h] and [00h 01h 00h 03h], the corresponding prl
is 000100020003 containing playback resources 01, 02, and 03
each with the prefix 00.
minimum-pr: Minimum playback requirements
minimum-pr contains the Maximum Instantaneous Resource (MIR)
values from the first row of all MIR Count Tables corresponding
to the playback resources listed in prl. Only the largest
value from the values of the same resource is chosen.
minimum-prl is a sequence of two-digit hexadecimal numbers
encoded in US-ASCII. Thus, minimum-prl has an even number of
hexadecimal digits.
minimum-pr requires the use of prl, and the values in
minimum-pr must be in the same order as the resources in prl.
minimum-pr is the more important of minimum-pr and total-pr,
because it defines the minimum playback requirements.
Example: If the file includes the first rows of MIR Count
Tables such as [02h 00h] and [01h 01h] corresponding to the
above Playback Resource Lists, the corresponding minimum-pr is
020001. (02 is the largest of 2 and 1, 00 is the largest of 0,
and 01 is the largest of 1.)
total-pr: Total playback requirements
total-pr contains the MIR values from the last row of all MIR
Count Tables corresponding to the playback resources listed in
prl. Only the largest value from the values of the same
resource is chosen. total-pr is a sequence of two-digit
hexadecimal numbers encoded in US-ASCII. Thus, total-pr has an
even number of hexadecimal digits.
total-pr requires the use of prl, and the values in total-pr
must be in the same order as the resources in prl.
Example: If the file includes the last rows of MIR Count Tables
such as [05h 02h] and [06h 01h] corresponding to the above
Playback Resource Lists, the corresponding total-pr is 060201.
(06 is the largest of 5 and 6, 02 is the largest of 2, and 01
is the largest of 1.)
Encoding considerations:
mobile-xmf data is binary data and must be encoded for non-binary
transport; Base64 [9] is suitable for Email.
Security considerations:
Many synthetic audio compositions have associated intellectual
property rights. It is conceivable that the rights owners of
mobile-xmf content will want to protect their rights by applying
security mechanisms that prohibit the rendering of the content
without a legally acquired license to do so. These mechanisms
would be applied externally to the Content-Type defined here;
mobile-xmf content itself is not encrypted internally. mobile-xmf
streams do not contain executable content. Mobile XMF players are
robust against corrupted mobile-xmf content, because Mobile XMF
players ignore unidentified content. prl, minimum-pr, and
total-pr parameters can be used to represent Mobile DLS playback
memory requirements for protecting against the excessive usage of
playback memory.
Interoperability considerations:
Mobile XMF is a Musical Instrument Digital Interface (MIDI)
specification developed by MMA and AMEI. Mobile XMF is based on
the XMF Meta File Format Specification v2.00 [5,6], which
standardizes a meta file format for the electronic distribution of
music. mobile-xmf data is stored in XMF file format [5,6].
Published specification:
Mobile XMF Content Format Specification, MMA specification v1.0.,
RP-42, Los Angeles, CA, USA. 2004.
Specification is available from:
http://www.midi.org/about-midi/specshome.shtml
Applications which use this media type:
mobile-xmf is a synthetic audio format for the flexible
presentation of SP-MIDI and Mobile DLS instrument data on a wide
range of playback devices, particularly portable appliances such
as mobile phones, PDAs, and palmtop computers.
Additional information:
Magic number(s):
First twelve bytes:
\130\115\106\137\062\056\060\060\000\000\000\002
File extension(s): mxmf
Macintosh File Type Code(s): mxmf
Person & email address to contact for further information:
Timo Kosonen
Email: timo.kosonen@nokia.com
Intended usage: COMMON
Restrictions on usage: none
Authors:
Timo Kosonen
Email: timo.Kosonen@nokia.com
Tom White
Email: twhite@midi.org
Change controller:
MIDI Manufacturers Association
P.O. Box 3173
La Habra, CA 90632-3173
Tel (714) 736-9774
Fax (714) 736-9775
Point of contact:
Tom White
Email: twhite@midi.org
3. Security Considerations
Security considerations are specified in the MIME subtype
registration contained in Section 2.
4. IANA Considerations
Section 2 of this document registers one MIME subtype.
5. Normative References
[1] Mobile XMF Content Format Specification, MMA specification v1.0.,
RP-42, Los Angeles, CA, USA. 2004.
[2] Mobile DLS, MMA specification v1.0., RP-41, Los Angeles, CA, USA.
2004.
[3] Scalable Polyphony MIDI Specification. December 2001, RP-034,
The MIDI Manufacturers Association, Los Angeles, CA, USA.
[4] Scalable Polyphony MIDI Device 5-24 Note Profile for 3GPP,
December 2001, RP-035, The MIDI Manufacturers Association, Los
Angeles, CA, USA.
[5] Specification for XMF Meta File Format, Version 1.00b. The MIDI
Manufacturers Association, Los Angeles, CA, USA, 2001.
[6] XMF Meta File Format 2.00, RP-043, MIDI Manufacturers
Association, Los Angeles, CA, USA, 2004
[7] MIDI 1.0 Detailed Specification, Document Version 4.2. February
1996, In 'The Complete MIDI 1.0 Detailed Specification, Document
Version 96.1.' The MIDI Manufacturers Association., Los Angeles,
CA, USA.
[8] Standard MIDI Files 1.0, In 'The Complete MIDI 1.0 Detailed
Specification, Document Version 96.1.' The MIDI Manufacturers
Association., Los Angeles, CA, USA.
[9] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
RFC 4648, October 2006.
Authors' Addresses
Timo Kosonen
Nokia
P.O. Box 100
33721 Tampere
Finland
Tel: +358 5048 35206
Fax: +358 7180 35899
EMail: timo.kosonen@nokia.com
Tom White
MIDI Manufacturers Association
P.O. Box 3173
La Habra, CA 90632-3173
USA
Tel: (714) 736-9774
Fax: (714) 736-9775
EMail: twhite@midi.org
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AI ELI5
On this page
§1Introduction
Mobile XMF is a compact audio format designed specifically for mobile devices. It was developed jointly by the MIDI Manufacturers Association (MMA) and the Association of Musical Electronics Industry (AMEI) to enable high-quality synthetic music on phones, PDAs, and similar devices.
Mobile XMF encapsulates two technologies: SP-MIDI (Scalable Polyphony MIDI) for music sequences, and Mobile DLS (Downloadable Sounds) for instrument definitions. The format is much smaller than standard MIDI files, making it ideal for music downloading and messaging on bandwidth-limited mobile networks. However, without a MIME type registration, systems had no standard way to identify and process these files.
Mobile XMF is a very small, high-quality music format made for phones and tablets. This RFC gives it an official name tag so systems know what to do with it.
§2The audio/mobile-xmf MIME Type
RFC 4723 registers the media type audio/mobile-xmf. This type has no required parameters, but supports three optional ones. The revision parameter carries the Mobile XMF file type revision ID from the XMF Meta File format. The prl (playback resource list) parameter describes which instrument resources are included in the file as two-digit hexadecimal codes.
The minimum-pr and total-pr parameters indicate playback resource requirements. These parameters help devices determine if they have enough memory and processing power to play the file. The parameters are encoded as sequences of hexadecimal digits and follow specific ordering requirements tied to the prl parameter.
The MIME type is audio/mobile-xmf. It can include optional notes like the file version and how much memory is needed to play the music.
§3File Format and Transport
Mobile XMF files are stored in XMF file format, which is based on the XMF Meta File Format Specification v2.00. The format is binary and contains both the music sequence (SP-MIDI) and the instrument definitions (Mobile DLS) in a single file.
For transport over non-binary protocols like email, Base64 encoding is recommended. The RFC specifies magic numbers (the first twelve bytes of a Mobile XMF file are fixed: \\130\\115\\106\\137\\062\\056\\060\\060\\000\\000\\000\\002), allowing systems to identify the file type by its header. File extensions are typically .mxmf, and the Macintosh file type code is also mxmf.
Mobile XMF files are binary (computer code), so for email they need to be converted to Base64 text. The file starts with a special signature so the system knows what it is.
§4Security and Interoperability
Mobile XMF content often has intellectual property rights. The RFC notes that copyright owners may apply security mechanisms externally to prevent unauthorized playback. Mobile XMF itself is not internally encrypted, and the format does not contain executable content. Mobile XMF players are designed to be robust against corrupted files, simply ignoring any unrecognized content.
The prl, minimum-pr, and total-pr parameters can serve a protective function by limiting resource consumption, preventing excessive memory usage during playback. Mobile XMF is based on the widely used MIDI specification and is designed for interoperability with a range of playback devices, from phones to handheld computers.
Music files might have copyrights, and some players could lock them with security. The format is safe because it doesn't run code, and players ignore parts they don't understand.
§5Applications and Use
Mobile XMF is intended for music downloading, ringtones, and music messaging on portable devices. The compact size makes it practical for these uses. Applications include mobile phones, PDAs, and other handheld devices that need to play synthetic audio without the overhead of larger MIDI or audio file formats.
The intended usage is marked as COMMON, indicating that the format is suitable for widespread deployment. The MIDI Manufacturers Association maintains control and management of the namespace and the format specification through the change controller role specified in this RFC.
Mobile XMF is used for ringtones, downloaded music, and text message attachments on phones. It's much smaller than other music formats, so it fits on limited devices.