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The ever increasing size and number of digital displays, combined with the introduction of ever-higher image resolutions, has greatly increased the complexity of local signal management in public venues; like sports arenas, concert halls and theatres. These complex environments need equally complex systems that are capable of routing a large number of sources to multiple displays and provide comprehensive switching and selection. In some cases there is also a need to mix and manipulate several video streams to provide eye-catching on-screen effects that raise the quality of entertainment and information delivered to the audience.
Large venues can have upward of two to three hundred screens, ranging from small wall-mounted LCD screens to giant LED matrix displays above a central arena or pitch. These are all expected to be managed as a single system with content shared between them with delivered to displays according to their locations.
Larger venues often have a wider range of sources and therefore need more complex switching and processing, as Felix Knight, Lightware, explains: “A major difference between venues is that the larger venue will typically have more sources that need to be incorporated into a production or event: multiple camera feeds, live streams, recorded material and so on. This increases the burden on signal routing and switching.” Interoperability between equipment is essential and a device that is difficult or impossible to integrate can present a real problem.
“Larger venues tend to have multiple configurations and the time taken to switch between them needs to be considered,” Knight adds. “In this way, a larger and more capable system can be justified if it reduces switching times between two configurations. Smaller venues do not tend to have such drastically different configurations, and if there are, the cost in time of repurposing the necessary hardware is not so great.”
It is not always the larger venues that have the most demanding requirements. Reliability of system operation is a massive factor, since the displays are so prominent, and as anyone who has experienced a system failure at a large public gathering can contest; they are highly noticeable by the audience. In extreme cases it can even rule the venue out of action with a potential loss of revenue.
Distribution of AV content over IP network offers some important benefits to installations that are spread over large physical areas. One of the most welcome advantages is that display points can be established wherever a network can be accessed. Knight summarises the benefits: “Whilst AV distribution over IP systems are not yet able to completely replace traditional pro AV systems, they are being considered in a wider range of applications than ever before. There is something of a sweet spot regarding cost and system size. Systems under this size are still most effectively handled by traditional AV systems, whilst systems above it can be handled by AV-over-IP much more efficiently.
“This technology comes with a set of advantages. It enables asymmetrical systems to be established with unequal numbers of inputs and outputs rather than the traditional ‘square’ format. It is scalable and can be built up to user requirements, without them having to invest in a larger matrix than initially needed. It is highly flexible and economic as it uses the standard IP protocol, so it is compatible with a lot of network switchers and existing Cat5 infrastructure.”
However, as he admits, there are disadvantages associated with AV-over-IP distribution technology. “The signal encoding-decoding process adds latency and it is necessary to compress the video to pass it around the limited bandwidth of the network. It may not be simple to incorporate new features, like HDR, into an existing distribution system and at some point the existing IP data network may be insufficient to handle heavy AV-over-IP traffic a separate network may be required. It is important for the IT department to be aware of this and accommodate new devices and technologies that they may need to be working with. AV-over-IP systems can only work well when the AV and the IT departments are coordinated. If they are not, huge network problems can occur.”
Latency can be a drawback in applications that take advantage of advanced real-time video processing. This needs to be carefully considered and the total end-to-end system latency calculated, particularly for broadcast and live events in which lip-sync on stage-to-display stage systems is important and delay easily noticed.