Audio Over IP Building Pro AolP Systems with Livewire Steve Church Skip Pizzi ELSEVIER AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Focal press is an imprint of Elsevier Focal Press
Contents Acknowledgements xv Preface CHAPTER 1 Introduction to AolP l 1.1 Two to Tango 2 1.2 Arguments for AolP 3 1.2.1 Scalability 3 1.2.2 Cost Effectiveness 4 1.2.3 Convenience 4 1.2.4 Smooth Integration with Other IP-Based Systems 5 1.2.5 Talking the PC's Native Language 5 1.2.6 In the Tech Mainstream 5 1.2.7 Future-proofing 5 1.3 IP-Anything 6 1.4 What's the Catch? 6 1.5 Implementation and Integration 7 1.6 AolP in Use Today 10 1.7 The Bottom Line 11 CHAPTER 2 Network Engineering for Audio Engineers 13 2.1 TDM versus IP 14 2.1.1 Statistical Multiplexing 15 2.1.2 IP "Backplane" 16 2.2 Ethernet/IP Networks: Layering Model 17 2.2.1 Layer 1: Physical Interface 20 2.2.2 Layer 2: Ethernet and Switching 21 2.2.3 Layer 3: IP Routing 21 2.2.4 Layer 4: Transport 21 2.2.5 Layer 5- Application 22 2.2.6 Making Packets 22 2.2.7 TCP 23 2.2.8 UDP 25 2.2.9 RTP 26 2.2.10 Ports 26 2.3 Local Area Networks 27 2.3.1 Ethernet Switching 27 vii
viii Contents 23.2 Ethernet Traffic Prioritization 28 2.33 The Role of TCP for Audio on LANs 29 23.4 VLANs 30 23.5 Ethernet Multicast 31 23.6 IGMP 32 23.7 ARP 33 2.4 Wide Area Networks and the Internet 34 2.4.1 The Internet 34 2.4.2 Private WANs 35 2.4.3 VPNs 36 2.4.4 DNS 36 2.4.5 DHCP 37 2.4.6 IP Broadcast 38 2.4.7 IP Multicast 38 2.4.8 Firewalls 38 2.4.9 NATs 39 2.5 Quality of Service 40 2.5.1 Bandwidth 41 2.5.2 Dropped Packets 41 2.5.3 Delay and Jitter 42 2.5.4 Service Level Agreements 42 2.5.5 MPLS 42 2.6 IP and Ethernet Addresses 43 2.6.1 IP Addresses 43 2.6.2 Subnets and the Subnet Mask 44 2.63 Ethernet Addresses 46 2.7 Network Diagrams 47 2.8 Pro-Audio, Meet IP 49 CHAPTER 3 Switching and Routing 51 3.1 Layers and Terms 51 3.2 Ethernet Switch 53 3.2.1 Managed Switches 53 3.2.2 Scalability 54 3.3 IP Router 54 33-1 Routes of the Internet 54 33.2 TCP/IP Suite 56 3.4 Straddling Layers 56 3.5 Audio Routing Control 58 3.6 Multicasting 59
Contents ix CHAPTER 4 Livewire System 63 4.1 What Can You Do with It? 63 4.2 AES3 65 4.3 Livewire System Components 66 4.3.1 Axia Hardware Interface Nodes 68 4.3.2 Router Selector Node 68 4.3-3 GPIO Node 69 4.3.4 Axia Driver for Windows 69 4.3.5 iplay (PC Router Selector) 71 4.3.6 Axia Element Mixing Console 73 4.3.7 Pathfinder Routing Control Software 74 4.3.8 Axia Intercom System 79 4.3.9 Telos iport Codec 81 4.3.10 Telos Nxl2 and Nx6 Telephone Interfaces 81 4.3.11 Omnia 8x Dynamics Processor 82 4.3.12 Fraunhofer Institute "Content Server" Encoders 82 4.4 Channel Numbering and Naming 82 4.4.1 Channel Numbers 83 4.4.2 Text Name 83 4.4.3 Sources and Destinations 84 4.4.4 Backfeeds and Mix-Minus 84 4.4.5 GPIO 84 4.4.6 V-Mix and V-Mode 87 4.5 Delay 87 4.6 Levels and Metering 90 4.6.1 Headroom 90 4.6.2 Alignment 93 4.6.3 International Variants 94 4.6.4 Terminology of Audio Level Metering 96 4.6.5 Livewire Levels 98 4.6.6 Aligning Consoles to PC Audio Applications 98 4.7 Deep Stuff How the Livewire Technology Works 99 4.7.1 Quality of Service 99 4.7.2 Source Advertising 100 4.7.3 Synchronization 100 4.7.4 Livewire's Use of Multicast Ethernet and IP Addresses 102 4.7.5 Livewire Packet Format 103 4.7.6 Link Capacity 106 4.7.7 Network Time Protocol 106
x Contents 4.7.8 Network Standards and Resources 106 4.8 Livewire Routing Control Protocol 107 4.9 Livewire Control Protocol 108 CHAPTER 5 Designing and Building with AolP 113 5.1 Wiring the AolP Facility 113 5.1.1 Simplification via Cabling 113 5.1.2 Structured Wiring 113 5.1.3 Ethernet for AolP Systems 114 5.1.4 Twisted-Pair Cable Categories 115 5.1.5 Structure of Structured Wiring 116 5.1.6 Pin Numbering, Jacks, Cables, and Color Codes 116 5.1.7 Installing RJ-45s 120 5.1.8 Special Care for AolP Wiring 121 5.1.9 Minimizing Pairs in a Cable 122 5.1.10 Patch Panels 122 5.1.11 Wall Jacks 123 5.1.12 Power over Ethernet 125 5.1.13 Fiber 125 5.1.14 Beyond Cable: Ethernet Radio Links 128 5.1.15 Analog and AES3 Audio Cabling 129 5.1.16 Microphone Connections 131 5.1.17 Unbalanced Connections 131 5.2 Ethernet Switches and IP Routers for Livewire 132 5.2.1 Switch Configuration 133 5.3 AolP Applications and Architectures 134 5.3.1 AolP "Snake" 134 5.3.2 Networkable PC Sound Card 135 5.3.3 Studio-to-Transmitter Link 135 5.3.4 Simple Radio Studio 136 5.3.5 Full-Fledged Radio Facility 137 5.3.6 Livewire "Classic" Radio Studio Setup 139 5.3.7 Audio Router 140 5.3.8 A 50+ Studio Facility with Redundancy 141 5.4 More on Architectures 141 5.4.1 Daisy-Chaining l4l 5.4.2 Redundancy 142 5.4.3 Security 143
Contents xi CHAPTER 6 VoIP Telephone Systems in the Studio Environment 145 6.1 VoIP in Radio Stations 146 6.2 SIP 148 6.2.1 Parts of a SIP System 149 6.2.2 Addressing 151 6.2.3 How SIP Works 152 6.2.4 The State of SIP and Its Future 154 6.3 IAX as a SIP Alternative 155 6.4 Codecs 156 6.5 Packetization and RTP 159 6.6 Delay 160 6.7 IP PBX 162 6.7.1 Cisco 162 6.7.2 Microsoft 166 6.7.3 Asterisk 169 6.7.4 Others 170 6.8 Gateways 170 6.8.1 Overview of Circuit-Switched Interfaces 171 6.9 Using VoIP to Connect to the Telco Network 175 6.9.1 MPLS 176 6.9.2 IP Centrex and Hosted PBX Services 176 6.10 Skype 180 6.11 Studio On-Air Systems 181 6.11.1 Line Echo Cancellation 182 6.11.2 Audio Processing 183 6.11.3 Acoustic Echo Cancellation 183 6.11.4 Application Example: Telos VX System 185 6.12 Application Examples: Telos Nx6 and Nxl2 190 6.13 Transformative Tech 190 CHAPTER 7 IP Codecs 191 7.1 The Challenge 192 7.2 When Delay Doesn't Matter 193 7.3 When Delay Does Matter: Achieving Low Delay 194 7.3.1 Audio Coding 194 7.3.2 Transport 195 7.3.3 Adaptive Receive Buffer 195 7.3.4 Adaptive Codec Bitrate 196 7.3.5 Putting It Together 196
xii Contents 7.4 Delay and Echo 197 7.5 Call Setup: Say Hello to SIP (Again) 197 7.6 SIP Servers 198 7.6.1 Firewalls and NATs 198 7.6.2 Telos Z/IP Server 199 7.7 Networks 200 7.7.1 Public Internet 200 7.7.2 Dedicated Links 200 7.7.3 MPLS Service 201 7.7.4 Mobile IP Services 201 7.7.5 Ethernet Radios 201 7.7.6 WiMax 201 7.7.7 WiEi 202 7.7.8 Satellites 202 7.8 EBU N/ACIP Standard 202 7.8.1 Transport Protocols 203 7.8.2 Audio Coding 203 7.8.3 Signaling 204 7.8.4 What's Missing from N/ACIP? 204 7.9 Livewire-Enabled IP Codecs 205 7.9.1 Telos Z/IP 205 7.9.2 Telos iport 206 7.10 Convergence 210 CHAPTER 8 Troubleshooting 213 8.1 Prevention 213 8.2 Basic Network Tests and Diagnostics 213 8.2.1 Link Test 213 8.2.2 Ping and TraceRoute 214 8.2.3 Rate and Duplex Modes 214 8.3 Ethernet Switch Diagnostics and Configuration 215 8.3.1 Link, Activity, Duplex, and Rate LEDs 215 8.3.2 Advanced Switch Diagnostics 215 8.3-3 Switch Configuration 215 8.4 Cable Testers 217 8.5 Sniffers 217 8.6 Livewire Components 218 8.6.1 Livewire Node Network Status LEDs 220 8.6.2 Checking Audio Levels 222
Contents xiii 8.7 Logging 222 8.7.1 Element Console 223 8.7.2 Pathfinder PC 224 CHAPTER 9 FAQs 231 9.1 Reliability 231 9.2 Cost Effectiveness 233 9.3 Latency 234 9.4 Interconnection 234 9.5 Livewire-Specific Issues 236 References and Resources 241 Glossary of Acronyms 245 Index 253