Technical Summary
The MPEG-4 standard specifies compression of audio-visual data into
for example an audio or video elementary stream. In the MPEG-4
standard, these streams take the form of audio-visual objects that may
be arranged into an audio-visual scene by means of a scene
description. Each MPEG-4 elementary stream consists of a sequence of
Access Units; examples of an Access Unit (AU) are an audio frame and a
video picture.
This specification defines a general and configurable payload
structure to transport non-multiplexed MPEG-4 elementary streams, in
particular MPEG-4 audio (including speech) streams, MPEG-4 video
streams and also MPEG-4 systems streams, such as BIFS (BInary Format
for Scenes), OCI (Object Content Information), OD (Object Descriptor)
and IPMP (Intellectual Property Management and Protection) streams.
The RTP payload defined in this document is simple to implement and
reasonably efficient. It allows for optional interleaving of Access
Units (such as audio frames) to increase error resiliency in packet
loss.
This payload format is largely compatible with the video part
of RFC 3016, the RTP Payload Format for MPEG-4 Audio/Visual Streams, and
extends that format to effectively support other classes of media and also
MPEG-4 Systems streams.
The specification registers the MIME sub-types audio/mpeg4-generic,
video/mpeg4-generic and application/mpeg4-generic.
MPEG-4 Systems supports stream types including commands that are
executed on the terminal like OD commands, BIFS commands, etc. and
programmatic content like MPEG-J (Java(TM) Byte Code) and
CMAScript. The Security Considerations discuss risks associated with
these capabilities and ways to mitigate these risks.
Working Group Summary
This was a strenuous effort by the AVT Working group.
This payload format has been under development since the 39th IETF meeting
in Munich, August 1997. It is the result of collaboration between AVT, the
MPEG committee and the Internet Streaming Media Alliance. When the
consensus designs were achieved, there was a thorough Last Call review and
strong support for advancement.
Protocol Quality
The specification was reviewed for the IESG by Allison Mankin.