pass subtypes of "image" that they do not specifically recognize to a
   secure and robust general-purpose image viewing application, if such
   an application is available.

   NOTE: Using of a generic-purpose image viewing application this way
   inherits the security problems of the most dangerous type supported
   by the application.

4.3.  Audio Media Type

   A media type of "audio" indicates that the body contains audio data.
   Although there is not yet a consensus on an "ideal" audio format for
   use with computers, there is a pressing need for a format capable of
   providing interoperable behavior.




 
RFC 2046                      Media Types                  November 1996


   The initial subtype of "basic" is specified to meet this requirement
   by providing an absolutely minimal lowest common denominator audio
   format.  It is expected that richer formats for higher quality and/or
   lower bandwidth audio will be defined by a later document.

   The content of the "audio/basic" subtype is single channel audio
   encoded using 8bit ISDN mu-law [PCM] at a sample rate of 8000 Hz.

   Unrecognized subtypes of "audio" should at a miniumum be treated as
   "application/octet-stream".  Implementations may optionally elect to
   pass subtypes of "audio" that they do not specifically recognize to a
   robust general-purpose audio playing application, if such an
   application is available.

4.4.  Video Media Type

   A media type of "video" indicates that the body contains a time-
   varying-picture image, possibly with color and coordinated sound.
   The term 'video' is used in its most generic sense, rather than with
   reference to any particular technology or format, and is not meant to
   preclude subtypes such as animated drawings encoded compactly.  The
   subtype "mpeg" refers to video coded according to the MPEG standard
   [MPEG].

   Note that although in general this document strongly discourages the
   mixing of multiple media in a single body, it is recognized that many
   so-called video formats include a representation for synchronized
   audio, and this is explicitly permitted for subtypes of "video".

   Unrecognized subtypes of "video" should at a minumum be treated as
   "application/octet-stream".  Implementations may optionally elect to
   pass subtypes of "video" that they do not specifically recognize to a
   robust general-purpose video display application, if such an
   application is available.

4.5.  Application Media Type

   The "application" media type is to be used for discrete data which do
   not fit in any of the other categories, and particularly for data to
   be processed by some type of application program.  This is
   information which must be processed by an application before it is
   viewable or usable by a user.  Expected uses for the "application"
   media type include file transfer, spreadsheets, data for mail-based
   scheduling systems, and languages for "active" (computational)
   material.  (The latter, in particular, can pose security problems
   which must be understood by implementors, and are considered in
   detail in the discussion of the "application/PostScript" media type.)





 
RFC 2046                      Media Types                  November 1996


   For example, a meeting scheduler might define a standard
   representation for information about proposed meeting dates.  An
   intelligent user agent would use this information to conduct a dialog
   with the user, and might then send additional material based on that
   dialog.  More generally, there have been several "active" messaging
   languages developed in which programs in a suitably specialized
   language are transported to a remote location and automatically run
   in the recipient's environment.

   Such applications may be defined as subtypes of the "application"
   media type. This document defines two subtypes:

   octet-stream, and PostScript.

   The subtype of "application" will often be either the name or include
   part of the name of the application for which the data are intended.
   This does not mean, however, that any application program name may be
   used freely as a subtype of "application".

4.5.1.  Octet-Stream Subtype

   The "octet-stream" subtype is used to indicate that a body contains