Network Working Group P. Frojdh
Request for Comments: 4613 U. Lindgren
Category: Informational M. Westerlund
Ericsson
September 2006
Media Type Registrations for Downloadable Sounds
for Musical Instrument Digital Interface (MIDI)
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 Internet Society (2006).
Abstract
This document serves to register a media type for Downloadable
Sounds.
Table of Contents
1. Introduction ....................................................1
2. Security Considerations .........................................2
3. IANA Considerations .............................................2
3.1. Media Type for Downloadable Sounds .........................3
4. References ......................................................5
4.1. Normative References .......................................5
4.2. Informative References .....................................5
1. Introduction
The present document seeks to register a media type for Downloadable
Sounds (DLSes). The DLS format is used to define instruments for
widely used wavetable synthesizers associated with the standards
[DLS1, DLS2, MDLS]. DLSes and their associated standards are
maintained and defined by two organizations, the Musical Instrument
Digital Interface (MIDI) Manufacturers Association (MMA) and the
Association of the Musical Electronics Industry (AMEI).
The media type defined here is needed to identify DLS files correctly
when they are served over HTTP, included in multi-part documents, or
used in other places where media types are used.
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2. Security Considerations
The DLS format may contain audio, displayable text data, and modeling
parameters (a.k.a. articulation parameters). In addition, the DLS
format contains a so-called conditional chunk that is 'active' in the
sense that it affects the execution of a DLS file parser. However,
the DLS format does not currently define any scripting mechanism.
Clearly, it is possible to author malicious files that, for example,
contain large amounts of data always blocked by a conditional
statement; i.e., no synthesizer loads the instruments.
However, for DLS, clients can and usually do protect themselves
against these kinds of attacks. A key point is that conditional
chunks are optional, that is, a parser does not have to execute a
conditional chunk. However, if a parser evaluates a conditional
chunk, it is still possible to parse its content and draw to a
conclusion as to whether it is usable for a particular synthesizer
engine.
Note that selected metadata fields may include information partly
intended to protect the media against unauthorized use or
distribution. In this case, the intention is that alteration or
removal of the data in the field would be treated as an offense under
national agreements based on World Intellectual Property Organization
(WIPO) treaties.
DLS have an extensible structure, making it theoretically possible to
define metadata fields or media formats in the future that could be
used to induce particular actions of the recipient, and thus that
would present additional security risks. However, this type of
capability is currently not supported in the referenced
specifications.
There is no current provision in the DLS standard for encryption,
signing, or authentication within the file formats.
3. IANA Considerations
The IANA has registered the media type audio/dls, as specified in
Section 3.1. The registration uses the template present in
[RFC4288].
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RFC 4613 Media Type Registrations for MIDI September 2006
3.1. Media Type for Downloadable Sounds
Type name: audio
Subtype name: dls
Required parameters: None
Optional parameters: 'dls-type'
A comma-separated list of the
dls types (one or more) that the
file content conforms to. The
following values are specified:
0, 1, and 2 signify Downloadable
Sounds Level 1.1b content,
Downloadable Sounds Level 2.1
content, and Mobile Downloadable
Sound content, respectively. All
types that the content conforms
to should be indicated. Further
values (integers) may be
specified in the future, and any
unknown values shall be ignored.
If the parameter is not
specified, it corresponds to a
value equal to 0; i.e., the
content conforms to Downloadable
Sound level 1.1b.
Encoding considerations: DLS files are binary and should
be transmitted in a suitable
encoding without CR/LF
conversion, 7-bit stripping
etc.; base64 [RFC3548] is a
suitable encoding.
Security considerations: see the security considerations
in Section 2 of RFC 4613.
Interoperability considerations: This media type is for
consumption by a MIDI player
capable of utilizing
downloadable sounds for its
synthesizers. A general-purpose
audio player will not be capable
of utilizing the audio within
the format without explicit
support of the format.
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RFC 4613 Media Type Registrations for MIDI September 2006
Published specification: Downloadable Sounds Level 1.1b
[DLS1], Downloadable Sounds
Level 2.1 [DLS2], and Mobile
Downloadable Sounds [MDLS]. MMA
specifications can be ordered
from the MMA web site,
www.midi.org.
Applications that use this media type: Multi-media
Additional information:
Magic number(s): The ninth to twelfth bytes of
the file must equal (in
hexadecimal notation) 44, 4c,
53, and 20, respectively.
File extension(s): .dls is declared at
http://www.nist.gov/nics
Person & email address to contact for further information:
Ulf A. Lindgren,
ulf.a.lindgren@ericsson.com
Intended usage: COMMON
Restrictions on usage: None
Author: Per Frojdh
Ulf A. Lindgren
Magnus Westerlund
Change controller: MIDI Manufacturers Association
http://www.midi.org
info@midi.org
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4. References
4.1. Normative References
[DLS1] "Downloadable Sounds Level 1.1b", MMA/AMEI specification
v1.1b, Los Angeles, CA, USA, 2004.
[DLS2] "Downloadable Sounds Level 2.1", MMA/AMEI specification
v1.0, Los Angeles, CA, USA, 2001.
[MDLS] "Mobile Downloadable Sounds 1.0", MMA specification v1.0,
Los Angeles, CA, USA, 2004.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
4.2. Informative References
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003.
Authors' Addresses
Per Frojdh
Ericsson AB
Ericsson Research
SE-164 80 Stockholm
Sweden
EMail: per.frojdh@ericsson.com
Ulf A. Lindgren
Ericsson AB
Ericsson Research
SE-417 56 Goteborg
Sweden
EMail: ulf.a.lindgren@ericsson.com
Magnus Westerlund
Ericsson AB
Ericsson Research
SE-164 80 Stockholm
Sweden
EMail: magnus.westerlund@ericsson.com
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RFC 4613 Media Type Registrations for MIDI September 2006
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RFC, FYI, BCP