Monitor walls
Sep 1, 2007 12:00 PM, BY KEVIN JACKSON
Modern video walls provide high-quality images and operational flexibility.
Source monitoring
Two Arqiva OB vehicles benefit from the operational flexibility of Predator HD8 multiviewers from Zandar Technologies. Image courtesy Arqiva.
Once purely simple screen splitters, multiviewers have evolved to meet this requirement, providing a host of monitoring capabilities. For example, new viewers offer extensive alarm capabilities. They are capable of detecting a large number of the technical faults most commonly encountered in a playout environment, and will automatically issue an on-screen alarm.
Video errors such as loss of video sync, frozen picture, black picture, EDH issues and missing ancillary data can be automatically detected. Audio errors, such as silence, over-level and phase error, can be continuously checked for, with any faults quickly rendered on screen, allowing the operator to react appropriately.
While the trend toward HD has been a key driver in the development of monitor walls, broadcast facilities are only gradually transitioning from SD to HD. Today's video wall needs to be capable of managing a mixture of video formats and aspect ratios, and designed accordingly. For example, a video wall must be capable of displaying 4:3 sources alongside 16:9 sources, as maintaining the correct aspect ratio is vital to avoid cutting elements from a picture.
The presence of 4:3 indicators on 16:9 sources is also a key requirement, to allow a production supervisor to view how an image will be displayed on different aspect ratio TVs in viewers' homes. With a multiviewer, the decoding of embedded aspect-ratio information can be used to automatically set the aspect ratio on sources, ensuring that the broadcaster has confidence in the source being presented correctly.
The more channels a video wall is charged with handling, and the greater the variety of sources for those channels, the harder it is for an operator to gain an instant overview of the state of play. In a crowded video wall, there is more emphasis on the ability to quickly identify a video window, and to quickly extract all status information for that source, such as video standard (PAL, SDI, HD-SDI), physical routing, logical name, channel ident, and other types of ancillary data embedded within the source.
Flexible layouts
Today's video wall has the advantage of being truly flexible. Where once a stack of CRTs was a fixed feature, the look and even style of a video wall can now be reconfigured as monitoring requirements change. For instance, “off-air” channels can be removed from view by switching between predefined layouts, and monitoring requirements can also vary to avoid raising unnecessary alarms. Flexibility of image sizing and positioning allows users to set their own priorities, enlarging important windows for quality assessment or displaying smaller windows from sources that are being shown for confidence monitoring only.
Incorporating a multiviewer solution as part of the build brings users an important step closer to the ideal of the truly virtual monitor wall. A multiviewer reduces the number of elements in a wall design that need to be fixed — both physically and operationally. But it is not the technological equivalent of a blank check. Careful consideration must still be given to the number of channels required, the format and resolution of the signals converging on the wall, the amount of audio monitoring needed, and so on.
As all monitoring is being brought to a single point by advances in video wall capabilities, reliability and redundancy are becoming of greater importance. Potential failure points in the transmission chain need to be kept to a minimum, and no facility can afford to lose monitoring, so the ability to reroute sources quickly from one monitor to another can be vital in emergencies.
The reliability of a multiviewer is crucial, and viewers should have dual-redundant power supplies so that in the unlikely event of a power supply failing, the power supply can be removed and replaced without the need to power down the system.
Video walls have evolved greatly in a few short years, and they are not finished yet. More sources and more information will find their way onto the wall, and building a modern wall is as much about predicting future trends as it is catering to contemporary challenges.
Kevin Jackson is product manager of broadcast and AV at Zandar Technologies.
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