It can’t be that simple can it? I mean, transporting time-sensitive data like video and audio over IP networks can’t be easy. Ensuring real-time data gets to where it needs to go, along with getting to grips with how the various technologies, protocols and transport mechanisms of Ethernet and IP networks work together can be daunting.
Well, Ethernet networks have come a long way since the days of 100Base-T and Ethernet hubs, and now do most of the heavy-lifting for you. So consider some of the new technologies on offer and see how they can facilitate time-sensitive AV transport.
AV over IP is a hot topic these days. And so it should be. The days of legacy AV distribution systems using dedicated, proprietary matrix switches have had their time. Yes, they served a purpose when dedicated AV systems were pretty much the only option available if you wanted to distribute AV signals around a building, campus or area but now there is a different way. A simpler way. A more resource-efficient, system-integrated and a more centrally accessible, yet at the same time, flexibly distributed way.
And the best news is that on many site installations, the infrastructure required to deploy all this is already there. It is of course, the IP network.
This post gives an overview of AV over IP – the defining, major trend in the AV industry today. It discusses some of the popular standards and protocols it uses (e.g Ethernet, TCP/IP, UDP) their relative strengths and weaknesses, and the issues and considerations AV designers, installers and consultants must consider to support this technology.
Well, as the name implies, AV over IP simply means using an IP network (in many cases this could just mean a network switch) as the transport mechanism for the sending and receiving of AV signals and data (audio, video, management traffic) between AV devices. This is a departure from the traditional AV distribution model of using the separate, distinct and proprietary infrastructure of a matrix switch.
Just as millions of IP devices (known as hosts) connected to networks around the world are able to send and receive data to each other over an IP network, AV over IP simply means that IP aware AV devices such as encoders and decoders are able to do exactly the same thing.
Being regular IP hosts they connect to each other using the same standards and protocols to distribute and receive encoded video and audio signals across the network. That means that any type of signal requiring switching, be it audio, video, KVM etc, is treated as just another IP stream and so can be routed dynamically to the intended recipient right across the same AV system. And all this using widely adopted, standards based technologies rather than specific vendor defined proprietary options is, simply, one of the biggest plus’s in anyone’s book for adopting AV over IP.
In the examples shown here, the data rate required is dependent on whether the AV over IP devices are compressing the video and audio signals prior to transmitting them over the network. Uncompressed video will need a higher data rate, but will deliver virtually no pixel loss and very low latency. Compressed video will consume less bandwidth, but will experience some pixel loss and have higher latency. Ethernet provides transmission rates of 1000Mbps and 10000Mbps. The faster the data rate, the more ‘transparent’ the network.
Ethernet is by far the most common link-level transport system for AV over IP but the transport mechanism is in itself secondary. The real intelligence lies in collection of protocols that run above it, commonly known as TCP/IP. This set of protocols accommodates different kinds of data for different kinds of applications. For example, File Transfer Protocol (FTP) supports local and remote file transfers between hosts, Simple Mail Transfer Protocol (SMTP) supports e-mail, Hypertext Transfer Protocol (HTTP) supports web applications. Of all the protocols in the TCP/IP suite, UDP and IP are the most important to AV over IP.
Switches make the AV over IP network
In the early days of Ethernet, hubs were used to connect hosts and devices to the network, but these indiscriminately broadcast packets (or more accurately, frames) to all hosts. Then switches were introduced, and these more efficient network appliances only pass packets to their intended destinations. This means that traffic – even high bandwidth traffic such as uncompressed video – can flow between hosts without clogging up precious network resources.
Intelligent switches also make it possible to virtually segment the network up using Virtual Local Area Networks, or VLANs. Although Ethernet itself by definition is not deterministic, thoughtful planning of your network can create areas or zones of determinism. Using intelligent switches to partition devices on a virtual or even physical network segments can provide enough governance for all but the most demanding applications, and this includes uncompressed AV over IP.
Traditionally, audio visual signal transmission relied upon using specific types of cables for sending audio or video signals between the different AV devices in a system. The cables used depended on what the sources were and what needed to be sent. Sources could be ‘any’…and ‘many’ including video cameras, laptop PC’s, media players, satellite receiver boxes etc..to name a few. So twisted shielded pair cabling for audio mic, twisted pair for speakers, coaxial for video and audio along with HDMI cabling for example could all be present in a system, but all would be required to be routed independently from source to display.
The cost of all this cabling would vary substantially, and so would the various types of connectors and terminators needed, and not to mention the labour costs of course involved to carry out this varied work. And further complications arise when the expectation is for dynamic routing between different sources to displays is required. It’s easy to see how an AV system can grow into a disparate infrastructure of varying device, cabling and software types to in order to satisfy the full expected audio and visual requirements.
The difference with using Ethernet networks is that each AV device can treated as just another IP endpoint in the network, with standard category x cabling (e.g Cat6, Cat6A) or fibre as well as standard network equipment such switches and routers. As the industry moves more and more towards transporting video signals over IP, AV users and AV professionals alike are finding that using a standards based infrastructure helps reduce the time and costs of AV installation, deployment and support.