Chances are you’ve heard of audio/video bridging (AVB). Chances are even better you don’t really know what it is. Read on, because AVB technology offers some real advantages over SDI, the kind of benefits that mesh with the new IT-driven video landscape.
The professional media transport market is still dominated by point-to-point analog wiring systems. (See Figure 1.) But there is an explosion of digital networks steadily replacing analog cabling and point-to-point digital cables for more scalable, flexible and high-performance AV systems. The dominance of digital signal processing, continual improvement in the price and performance of networking technologies, widespread deployment of IT networks and the increasing use of computer equipment for playback, storage, and processing of media signals are all driving digital adoption. Now that AV equipment can be networked without sacrificing performance, the AV and IT industries are converging, enabling new AV applications and collaborative, networked systems.
Yet, for all of its promise, conventional IT networking has lacked the precise timing needed by the professional broadcast environment. AVB’s primary drive is to add the timing precision so professionals can rely on traditional performance from inexpensive, off-the-shelf network fabrics. The IT industry has, in a sense, caught up, delivering the speed and reliability demanded by broadcasters and content providers.
AVB, an open standard established by the IEEE, is a group of network protocols for the distribution of time-synchronized, low-latency audio and video streams over Ethernet. All audio and video streams, as well as associated control, metadata and synchronization needed for a live production, are on a single cable/layer — one connection that works as both an input and output.
The highly scalable IT-based system enables the use of current as well as new standards, such as 4K, with standard, off-the-shelf switches with software on top, providing broadcasters with predictable, reliable, consistent and uncompressed video delivery. The system is synchronous on top of a asynchronous network. What you put in is what you get out for stable, fast, low-latency transport with an overall network delay of 2ms.
AVB technology lays the foundation for high-quality, low-latency guaranteed media streaming over Ethernet networks. The three core protocols allow for timing and synchronization, bandwidth allocation through the stream reservation protocol (SRP) and traffic shaping to ensure that low-priority Ethernet traffic does not interfere with critical AVB video traffic. AVB devices also periodically exchange timing information so both ends of the link synchronize their time base reference clocks precisely for synchronization of multiple streams.