RTP Payload Format for Real-Time Pointers
RFC 2862

Document Type RFC - Proposed Standard (June 2000; No errata)
Last updated 2013-03-02
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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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