Network Working Group T. Edwards
Request for Comments: 4539 PBS
Category: Informational May 2006
Media Type Registration for the
Society of Motion Picture and Television Engineers (SMPTE)
Material Exchange Format (MXF)
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 the Society of
Motion Picture and Television Engineers (SMPTE) Material Exchange
Format (MXF). MXF, defined by SMPTE 377M, is a standard wrapper
format developed for the interchange of audiovisual material,
including both audiovisual essence and rich metadata.
Table of Contents
1. Introduction ....................................................2
2. Security Considerations .........................................3
3. IANA Considerations .............................................3
3.1. Media Type for SMPTE Material Exchange Format (MXF) ........3
4. References ......................................................5
4.1. Normative References .......................................5
4.2. Informative References .....................................5
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RFC 4539 Media Type Registration for MXF May 2006
1. Introduction
The present document registers a media type for SMPTE Material
Exchange Format (MXF). MXF, defined by SMPTE 377M [SMPTE377M], is a
standard wrapper format developed for the interchange of audiovisual
material, including both audiovisual essence and rich metadata.
Essence is the raw video, audio, and data streams contained and
described by MXF. Metadata carried by MXF includes structural
metadata and descriptive metadata. Structural metadata relates to
the structure and capabilities of the MXF file and is generally
required for proper decoding. Some examples of structural metadata
are descriptions of essence types, information to help synchronize
playout of audio and video, and content length. Descriptive metadata
gives information about the program content in the file and is not
essential for decoding. Some examples of descriptive metadata are
program title, actors, and scene descriptions. The essence in MXF
files may itself carry data, such as vertical blanking interval data
used for carriage of Closed Captioning and other purposes.
MXF is an important tool in providing interoperation between
different video systems as well as digital cinema systems. MXF also
aids in the development of video production and distribution
workflows that are more efficient, multi-vendor, file based, and IT
oriented.
SMPTE currently has standards for the mapping of the following
essence types to the MXF generic container: MPEG (including MPEG-1
and MPEG-2 video streams, as well as MPEG audio), DV-DIF (Digital
Video Digital Interface Format for the DV family of related video
encodings), Uncompressed Pictures, SDTI-CP (Serial Digital Transport
Interface Content Package for delivering packetized audiovisual
content over the SDI interface), D-10 (a specialized video stream
incorporating MPEG-2 4:2:2P@ML), D-11 (a high-definition video
compression standard), AES3 audio, Broadcast Wave audio, and A-Law
audio. The flexibility of the MXF generic container allows for the
possibility of mappings of additional essence types in the future.
The media type defined here is needed to correctly identify MXF files
when they are served over HTTP or other network connections, included
in multi-part documents, indexed by operating systems and digital
asset management systems, or used in other places where media types
are used.
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RFC 4539 Media Type Registration for MXF May 2006
2. Security Considerations
Security requirements for the application/mxf media type are
discussed in the IANA media type registration (Section 3.1).
3. IANA Considerations
The IANA has registered the media type application/mxf as specified
in Section 3.1. The registration uses the template present in
[RFC4288].
3.1. Media Type for SMPTE Material Exchange Format (MXF)
To: ietf-types@iana.org
Subject: Registration of media type application/mxf
Type name: application
Subtype name: mxf
Required parameters: none
Optional parameters: ULs
The optional parameter ULs is a single Uniform Resource Name (URN),
or a comma-separated list of multiple URNs of SMPTE Universal Labels
(which are defined by SMPTE 400M [SMPTE400M]).
This optional parameter provides hints to the decoder regarding the
structure of the MXF file, which could include Operational Pattern,
essence types, descriptive metadata schemes, and other elements that
are identified by their SMPTE Universal Label.
SMPTE Universal Labels are Object Identifiers (OIDs), as specified by
[ASN1]. Thus, a URN of a SMPTE Universal Label can use the OID URN
namespace specified in [RFC3061], or any other future URN namespace
that is appropriate for SMPTE Universal Labels.
Note that, per [RFC2045], some characters (including the comma used
to separate multiple values) require that the entire parameter value
be enclosed in quotes.
Below is an example of use of the optional parameter. The two SMPTE
Universal Labels indicate that the MXF file uses the OP1a Operational
Pattern and contains IEC DV video at 25 Mbps, 525 lines, 59.94 fps
interlaced essence.
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RFC 4539 Media Type Registration for MXF May 2006
Content-Type: application/mxf;
ULs="urn:oid:1.3.52.4.1.1.1.13.1.2.1.1.1,
urn:oid:1.3.52.4.1.1.1.4.1.2.2.2.1.1"
Encoding considerations: binary
Security considerations: Application/mxf objects are not signed but
may be partially encrypted internally. External security mechanisms
must be employed to ensure content confidentiality. MXF, through
metadata extensions, may allow executable code to be transferred in
the file. It is suggested that no unauthenticated executables
decoded from an MXF file be executed. Some compressed essence types
carried in MXF may carry a risk that certain pathological bitstreams
could lead to potential denial-of-service attacks against these
essence decoders.
Interoperability considerations: MXF provides a standard wrapping for
a number of audio and video essence types according to a number of
different Operational Patterns (OP). Thus, interoperability depends
upon whether the MXF file decoder has the capability to match the
features of the MXF file encoder. An Application Specification (AS)
can ensure that MXF encoders and decoders can interoperate
effectively.
Published specification: RFC 4539, SMPTE 377M [SMPTE377M]
Applications that use this media type: MXF is a wrapper for many
types of audio and video essence types in use by many applications in
the broadcast and digital cinema industries. These include
non-linear editing systems, video servers, video camera systems,
digital asset management systems, and digital video distribution
systems.
Additional information:
Magic number(s): none
File extension(s): .mxf
Macintosh File Type Code(s): "mxf "
Person & email address to contact for further information:
Thomas Edwards
email: tedwards@pbs.org
Intended usage: COMMON
Restrictions on usage: none
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RFC 4539 Media Type Registration for MXF May 2006
Author/Change controller:
Thomas Edwards
email: tedwards@pbs.org
4. References
4.1. Normative References
[SMPTE377M] Society of Motion Picture and Television Engineers,
"Material Exchange Format (MXF) File Format
Specification", SMPTE 377M-2004, <http://www.smpte.org>.
[SMPTE400M] Society of Motion Picture and Television Engineers,
"SMPTE Labels Structure", SMPTE 400M-2004,
<http://www.smpte.org>.
4.2. Informative References
[ASN1] International Telephone and Telegraph Consultative
Committee, "Specification of Basic Encoding Rules for
Abstract Syntax Notation One (ASN.1)",
CCITT Recommendation X.209, January 1988.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC3061] Mealling, M., "A URN Namespace of Object Identifiers",
RFC 3061, February 2001.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December
2005.
Author's Address
Thomas G. Edwards
PBS
6453 Stephenson Way
Alexandria, VA 22312
US
Phone: +1 703 739 5000
EMail: tedwards@pbs.org
URI: http://www.pbs.org
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RFC 4539 Media Type Registration for MXF May 2006
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