Subject: I-D ACTION:draft-ietf-avt-rtp-h263-video-00.txt

From: [email-masked]
Date: Mon, 17 Nov 1997 10:38:57 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Audio/Video Transport Working Group of the IETF.

	Title		: RTP Payload Format for the 1998 Version 
                          of ITU-T Rec. H.263 Video (H.263+)
	Author(s)	: C. Bormann, L. Cline, G. Deisher, C. Maciocco,
                          T. Gardos, D. Newell, J. Ott, S. Wenger, C. Zhu 
	Filename	: draft-ietf-avt-rtp-h263-video-00.txt
	Pages		: 6
	Date		: 14-Nov-97
	
This document specifies an RTP payload header format applicable to the
transportation of video streams generated based on the 1998 version of
ITU-T Recommendation H.263.
 
The 1998 version of ITU-T Recommendation H.263 added numerous coding
options to improve codec performance over the 1996 version.  The 1998
version is referred to as H.263+ in this document.  Among the new
options, the ones with the biggest impact on the RTP payload are the
slice structured mode (SS), independent segment decoding mode (ISD), and
the scalability mode.  This section summarizes the impact of these new
coding options on packetization.  Refer to [4] for more information on
coding options.
 
Slice structure was added to H.263+ for three purposes: to provide
enhanced error resilience capability, to make the bitstream more
amenable to use with an underlying packet transport such as RTP, and to
minimize video delay.  The slice structured mode supports fragmentation
at macroblock boundaries.
 
When the independent segment decoding option is employed, a video
picture frame is broken into segments and encoded in such a way that
each segment is independently decodable.  Utilizing ISD in a lossy
network environment helps prevent the propagation of errors from one segment of the picture to others.
 
H.263+ also includes bitstream scalability as an optional coding mode.
Three kinds of scalability are defined: temporal, signal-to-noise ratio
(SNR), and spatial scalability.  Temporal scalability is achieved via
the disposable nature of bi-directionally predicted frames, or B-frames.
SNR scalability permits refinement of encoded video frames, thereby
improving the quality (or SNR).  Spatial scalability is similar to SNR
scalability except the refinement layer is twice the size of the base
layer in the horizontal dimension, vertical dimension, or both. 

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