RTP Payload Format for Real-Time Pointers
RFC 2862
| Document | Type |
RFC - Proposed Standard
(June 2000; No errata)
Was draft-ietf-avt-pointer (avt WG)
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf htmlized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 2862 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group M. Civanlar
Request for Comments: 2862 G. Cash
Category: Standards Track AT&T
June 2000
RTP Payload Format for Real-Time Pointers
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document describes an RTP [1] payload format for transporting
the coordinates of a dynamic pointer that may be used during a
presentation. Although a mouse can be used as the pointer, this
payload format is not intended and may not have all functionalities
needed to implement a general mouse event transmission mechanism.
1. Introduction
In most presentations, significant information is conveyed through
the use of viewgraphs and a pointer. This makes accurate transmission
of them vital in remote conferencing applications. Using regular
video of a presenter's display for this purpose is problematic
because, while the viewgraphs require a high spatial resolution, the
pointer movements need to be sampled and transmitted at a high
temporal resolution so that the presenter's pointing actions can be
displayed synchronously with the corresponding audio and video
signals. In many instances, this synchronization carries vital
information. As an example, consider a speaker pointing at two
alternatives on a viewgraph in sequence and saying "this one is
better than this". To satisfy both high spatial and high temporal
resolution requirements, at least S-VHS quality video may need to be
used. Codecs that can compress S-VHS video effectively in real-time
are expensive for this purpose, and transmitting such video
uncompressed requires very high bandwidths.
Civanlar & Cash Standards Track [Page 1]
RFC 2862 RTP Payload Format for Real-Time Pointers June 2000
A much simpler and economical system can be designed by capturing and
transmitting the pointer coordinates separately [2]. The pointer
coordinates with respect to a displayed viewgraph can easily be
obtained in electronic presentation systems. For presentations
prepared for optical systems, such as transparencies for overhead
projectors, an arrangement where the viewgraph is captured in a frame
buffer on a computer can be used to associate the pointer coordinates
with the displayed viewgraph. For capturing transparencies, printed
material, or even three dimensional objects, a document camera and a
personal computer or workstation based video capture card can be
used. This arrangement can handle electronic viewgraphs by feeding
the video output of the computer that displays them to the video
capture card through an appropriate converter also. A side benefit of
this is that it allows using a presenter's own computer to transmit
electronic viewgraphs without connecting it to, for example, an
intranet. The captured image is then displayed along with the
capturing computer's mouse pointer on the presenter's display using a
projector. The presenter moves the pointer on the display using a
regular or maybe a wireless mouse whose location can easily be
captured by appropriate software running on the capturing computer.
This document describes an RTP payload format to transmit the pointer
coordinates captured in one of the ways described above using RTP.
Although, a mouse can be used as the pointer, this payload format is
not intended and may not have all functionalities needed to implement
a general mouse event transmission mechanism.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [3].
Civanlar & Cash Standards Track [Page 2]
RFC 2862 RTP Payload Format for Real-Time Pointers June 2000
2. Payload Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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