Voice and video conferencing fundamentals

393 Pages·2007·3.956 MB·English

by  Scott Firestone, Thiya Ramalingam, Steve Fry

Voice and Video Conferencing
Fundamentals
Scott Firestone, Thiya Ramalingam, and Steve Fry
Cisco Press
800 East 96th Street
Indianapolis, IN 46240 USA
ii
Voice and Video Conferencing Fundamentals
Scott Firestone, Thiya Ramalingam, and Steve Fry
Copyright© 2007 Cisco Systems, Inc.
Published by:
Cisco Press
800 East 96th Street
Indianapolis, IN 46240 USA
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, recording, or by any information storage and retrieval system, without written permission from the pub-
lisher, except for the inclusion of brief quotations in a review.
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
First Printing: March 2007
ISBN-10: 1-58705-268-7
ISBN-13: 978-1-58705-268-2
Library of Congress Cataloging-in-Publication Data

Firestone, Scott.
Voice and video conferencing fundamentals / Scott Firestone, Thiya Ramalingam, and Steve Fry. -- 1st ed.
p. cm.
ISBN 978-1-58705-268-2 (pbk.)
1. Videoconferencing. 2. Internet telephony. I. Ramalingam, Thiya. II. Fry, Steve. III. Title. IV. Title: Voice and videoconferencing
fundamentals.

HF5734.7.F57 2007
006.7--dc20

2007003879
Warning and Disclaimer
This book is designed to provide information about voice and video conferencing. Every effort has been made to make this book as
complete and as accurate as possible, but no warranty or fitness is implied.
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The opinions expressed in this book belong to the author and are not necessarily those of Cisco Systems, Inc.
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Publisher: Paul Boger Cisco Representative: Anthony Wolfenden
Associate Publisher: Dave Dusthimer Cisco Press Program Manager: Jeff Brady
Executive Editor: Kristin Weinberger Technical Editors: Jesse J. Herrera, Nermeen Ismail
Managing Editor: Patrick Kanouse Copy Editor: Keith Cline
Development Editor: Dayna Isley Proofreader: Gayle Johnson
Senior Project Editor: San Dee Phillips
Team Coordinator: Vanessa Evans
Book and Cover Designer: Louisa Adair
Composition: Mark Shirar
Indexer: Tim Wright
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About the Authors
Scott Firestone holds a master’s degree in computer science from MIT and has designed
video conferencing and voice products since 1992, resulting in five patents. During his
10 years as a technical leader at Cisco, Scott developed architectures and solutions related to
video conferencing, voice and video streaming, and voice-over-IP security.
Thiya Ramalingam is an engineering manager for the Unified Communications organization at
Cisco. Thiya holds a master’s degree in computer engineering and an MBA from San Jose State
University. He holds several patents issued and pending, related to voice and video over IP. Thiya
is currently leading the development of multimedia conferencing products at Cisco.
Steve Fry is a technical leader in the Unified Communications organization at Cisco. For the past
several years, Steve has been involved in the design and development of telephony and
conferencing products. Prior to his conferencing projects, he was a principal engineer on the
CallManager MGCP gateway products. He is currently leading product development in video
conferencing.
About the Technical Reviewers
Jesse J. Herrera is a senior systems analyst for a Fortune 100 company in Houston, Texas. Mr.
Herrera holds a bachelor of science degree in computer science from the University of Arizona
and a master of science in telecommunication management from Southern Methodist University.
His responsibilities have included design and implementation of enterprise network architectures,
including capacity planning, performance monitoring, and network management services. His
recent activities include engineering and support roles in electronics business and retail system
services.
Nermeen Ismail is a technical leader in the TelePresence Systems Business Unit in Cisco. She
has more than 15 years of experience in academia and industry, focusing on multimedia
communications over packet networks. Nermeen has an engineering degree from Cairo University
and a master of science degree from University College London.
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Acknowledgments
Nermeen Ismail provided a cover-to-cover review of the book, lending considerable expertise in
video and voice over IP.
Jesse Herrera also provided a full review, verifying all parts of the text in minute detail.
The authors are particularly grateful to Stuart Taylor for providing a number of suggestions and
comments on the introduction and architecture chapters; to Tripti Agarwal for taking time to
review the H.323 section and provide her insight on CallManager signaling implementation
details; to Judy Gulla for doing a thorough review of the SIP chapter and providing valuable
comments; to William May for reviewing the media control chapter; and to Dan Wing, who was
instrumental in reviewing the security chapter.
We thank all the folks at Cisco Press. We especially thank Kristin Weinberger and Dayna Isley,
who helped take the basic material and create a real Cisco Press book. Thank you.
Thiya Ramalingam: I want to thank Johnny Chan, Shantanu Sarkar, and Walter Friedrich for
believing in me and encouraging me in every way with my career at Cisco. I also want to say thank
you to the architects and engineers who worked with me on the distributed video conferencing
project that was the inspiration for me to start this book.
Steve Fry: I want to thank Thiya Ramalingam for inviting me to collaborate with him on this book
and to Scott Firestone and the reviewers for their assistance in developing my contribution.
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Contents at a Glance
Foreword xviii
Introduction xix
Chapter 1 Overview of Conferencing Services 3
Chapter 2 Conferencing System Design and Architecture 21
Chapter 3 Fundamentals of Video Compression 45
Chapter 4 Media Control and Transport 105
Chapter 5 Signaling Protocols: Conferencing Using SIP 145
Chapter 6 Signaling Protocols: Conferencing Using H.323 185
Chapter 7 Lip Synchronization in Video Conferencing 223
Chapter 8 Security Design in Conferencing 257
Appendix A Video Codec Standards 327
Index 360
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Contents
Foreword xviii
Introduction xix
Chapter 1 Overview of Conferencing Services 3
Conference Types 3
Ad Hoc Conferences 4
Ad Hoc Conference Initiation: Conference Button 4
Ad Hoc Conference Initiation: Meet Me Button 5
Reservationless Conferences 5
Scheduled Conferences 6
Setting Up Scheduled Conferences 6
Joining a Scheduled or Reservationless Conference 8
Scheduled and Reservationless Conference Features 8
Voice and Video Conferencing Components 9
Video Conferencing Modes 11
Voice-Activated Conferences 11
Continuous Presence Conferences 13
Lecture Mode and Round-Robin Conferences 15
Types of Endpoints 16
Desktop Conferencing Systems 16
Room Conferencing Systems 16
Telepresence Systems 16
Video Controls: Far-End Camera Control 17
Text Overlay 18
Summary 18
Chapter 2 Conferencing System Design and Architecture 21
Components of a Conferencing System 21
User Interface 23
Web Portal 23
Voice and Telephony User Interface 24
Meet Me Button 24
Conference Control 25
Control Plane 26
Media Plane 27
Player/Recorder 27
Video Mixer/Compositor 27
Video Transrater 28
Video Transcoder 30
Audio Mixer 31
Conferencing Architectures 37
Centralized Architecture 37
Distributed Architecture 38
ix
Accessing the Focus 39
Conference Policy Server 39
Media Server 40
Full-Mesh Networks 40
Advanced Conferencing Scenarios 41
Escalation of Point-to-Point-to-Multipoint Call 41
Lecture Mode Conferences 41
Panel Mode Conference 42
Floor Control 42
Video Mixing and Switching Scenarios 42
Summary 43
References 43
Chapter 3 Fundamentals of Video Compression 45
Evaluating Video Quality, Bit Rate, and Signal-to-Noise Ratio 45
Video Source Formats 47
Profiles and Levels 47
Frame Rates, Form Factors, and Layouts 47
Standard and High Definitions 48
Color Formats 49
Basics of Video Coding 52
Preprocessing 52
Post-Processing 54
Encoder Overview 55
Transform Processing 55
Quantization 59
Entropy Coding 62
Binary Arithmetic Coders 68
DCT Scanning 69
Adaptive Encoding 71
Hybrid Coding 72
Hybrid Decoder 72
P-Frames 74
Hybrid Encoder 74
Predictor Loop 76
Motion Estimation 77
1/2 Pel and 1/4 Pel Motion Estimation 80
Conventions for Motion Estimation 81
Overlapped Block Motion Compensation 81
B-Frames 82
Predictor Loops for Parameters 86
Error Resiliency 88
Error Correction 89
Start Codes 89
x
Reversible VLCs 89
Data Dependency Isolation 90
Redundant Slices 90
Data Prioritization 90
Scalable Layered Codecs 91
SNR and Spatial Scalability 93
Temporal Scalability 95
Switching Frames 99
Video Codecs 100
Video Stream Hierarchy 100
Macroblocks 101
HD-Capable Codecs 102
Summary 102
References 103
Chapter 4 Media Control and Transport 105
Overview of RTP 105
RTP Header 107
First Octet in the Header 108
Payload Type 108
Sequence Number 109
Time Stamp 109
Synchronization Source Identifier 110
Contributing Source (CSRC) Identifiers 110
Payload Header 110
Payload 111
RTP Port Numbers 111
SSRC Collisions 111
RTP Header Extensions 112
Overview of RTCP 113
RTCP Packet Headers 113
RTCP Sender Report 114
RTCP Receiver Report 116
RTCP Source Description (SDES) 117
RTCP BYE 119
RTCP APP 120
RTP Devices in Conference Systems 120
RTP Translator 120
Media Termination Points 120
Transcoders and Transraters 122
RTP Mixer 123
Audio Mixer 123
Video MCU 124
Video Switcher 124