(registered 2009-07-07; last updated 2009-07-07)

http://standards.iso.org/ittf/PubliclyAvailableStandards/c050551_ISOIEC_21009_2005_Amd_2008_Annex_D.pdf

MIME media type name: application

MIME subtype name: mp21

Required parameters: none

Optional parameters: none

Encoding considerations: base64 is generally preferred; files are binary and should be
transmitted without CR/LF conversion, 7-bit stripping, etc. Note that although files
conforming to ISO/IEC 21000-2 are textual XML the mp21 file which contains it is binary.

Security considerations: It is possible to inject non-compliant MPEG streams (Audio, Video,
and Systems) in the MP21 file to overload the receiver/decoder's buffers. This might
compromise the functionality of the receiver or even crash it.
An MP21 file supports the storage of stream types, including commands that are executed on
the terminal such as Digital Item Methods based on ECMASCRIPT for which also bindings to
Java(TM) and C++ exists. It is possible to use one or more of the above in a manner non-
compliant to MPEG to crash the receiver or temporarily make it unavailable.
Authentication mechanisms can be used to validate of the sender and the data to prevent
security problems due to non-compliant malignant MP21 files.

Interoperability considerations: A number of interoperating implementations exist within
the ISO/IEC 21000 community, and that community has reference software for reading and
writing the file format.

Published specification: ISO/IEC 21000-9:2005

Applications which use this media type: Multimedia

Additional information:
Magic number(s): none
File extension(s): m21 and mp21 are both declared at http://www.fileinfo.net and
http://filext.com/.
Macintosh File Type Code(s): mp21 is registered with Apple.

Person & email address to contact for further information: David Singer, singer&apple.com
Intended usage: COMMON

Author/Change controller: David Singer, ISO/IEC 21000 file format chair