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)
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This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
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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
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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RFC 4613 Media Type Registrations for MIDI September 2006
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.
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.
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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RFC 4613 Media Type Registrations for MIDI September 2006
[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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