RFC4613
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.
Contents
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.
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.
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.
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.
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,
[email protected]
Intended usage: COMMON
Restrictions on usage: None
Author: Per Frojdh
Ulf A. Lindgren
Magnus Westerlund
Change controller: MIDI Manufacturers Association
http://www.midi.org [email protected]
References
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.
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: [email protected]
Ulf A. Lindgren Ericsson AB Ericsson Research SE-417 56 Goteborg Sweden
EMail: [email protected]
Magnus Westerlund Ericsson AB Ericsson Research SE-164 80 Stockholm Sweden
EMail: [email protected]
Full Copyright Statement
Copyright (C) The Internet Society (2006).
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