





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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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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   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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