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Design for OB trucks

Driven originally by the rapid migration to HD, the outside broadcast (OB) truck business has been buoyant over recent years. While stereoscopic 3-D is unlikely to have the same effect, it seems likely that there will be continued interest in building new trucks to meet the ever-increasing demands for remote productions.

All users have some clear ideas of what they want to achieve with an OB unit, which will lead them to specify at least some of the technical requirements. A specialist builder can contribute to the debate by taking these outline requirements and refining them into a detailed design that is best going to deliver what the operator requires.

For most operators, a new OB unit is a big investment that will earn a return on that investment over a long period. Five to 10 years is the minimum lifecycle. Ideally the vehicle itself and the specialist coach building will be expected to serve for more than 10 years, which means the original design and construction has to be right.

This article looks at some of the issues that an operator, a designer and a systems integrator will debate before agreeing upon a final design. Every unit is customized in some way for the particular needs of the operator, and it is vital to ensure that those needs are understood before the drawings even begin.

Consider application

The first point to consider is the application. Many headlines today are grabbed by the giants of OB, the double- and triple-expanding trailers capable of supporting 30 cameras or more. These are, of course, vital for the big sporting events, and there are many of them in service around the world.

Not every job requires this capacity. More importantly, a triple-expanding trailer requires a large amount of space in which to be set up. That is probably not important in a dedicated compound at a major sports venue, but is a major restriction in city centers.

If you have a production from, say, the Royal Opera House in London or La Scala in Milan, you need a compact unit because that is all that can be parked nearby. Not every sport takes place in a large, dedicated arena. Popular games like snooker, darts or poker take place in city center theatres or hotel ballrooms where the access is likely to limit the size of the vehicle. Big is not always better.

Conversely, whether the scale of the production is small or large, the same demands on creative technology will be present. For example, super slow-motion replays are an integral part of football or rugby coverage, but they are also required for smaller sporting events like snooker or darts and for theatre-based light entertainment such as ballroom dancing.

One solution is the ability to chain trucks. Two smaller units can work together as a single unit when the scale of the production requires it.


The key to the design of a successful OB truck — whatever its size — is flexibility. There should be a basic technical infrastructure and minimum equipment level to which additional facilities are added to meet the particular needs of the production.

Some camera channels will be permanent, adding others from a pool of stock as required. Server capacity, graphics devices and onboard editing can also be loaded into the truck on a job-by-job basis.

This requires two things. First, the desk layout must be readily adaptable to add control panels or other equipment when necessary. A flexible desk layout also allows the unit to accommodate the fact that different broadcasters and production companies have various ways of working and therefore will prefer key staff to be in different locations.

Some broadcasters and events have very particular requirements, such as a video referee in the truck, alongside a dedicated replay operator. When the UK's Channel 4 was the rights holder for test cricket, it initiated the idea of an analyst providing detailed comments, in vision, from a desk in the OB truck.

The second requirement is that the equipment racking should be equally flexible. When the truck is at its base, it is not earning money. That's why speed in installing and removing equipment is vital. Racks need good access from front and rear, and the cabling infrastructure must be flexible enough to support constantly changing requirements.

Developing the requirements specification from the likely applications and the flexibility required in operational and technical areas calls for careful discussions, and adequate time must be planned for this process. One of the major advantages of working with a systems integrator with experience in building OBs is that you will be able to draw on that experience in operational layouts and workflow.


The choice of main cameras is usually dictated by the operator, often because the vehicle will be part of a fleet and will need to draw on pooled equipment. Even if that is not the case, the operator is likely to need to hire in cameras on an occasional basis. Therefore, it will need to select a model that is widely available in the rental market.

Camera connectivity is a key issue. Triax is extremely rugged, widely used, easily supported and preinstalled in a large number of venues. Fiber is lighter where cables need to be pulled in and offers a significantly extended range. Cameras that can support either fiber or triax, and adaptive cabling systems, add flexibility.

Wireless cameras are a common requirement in all sorts of production. Clearly, a wireless system that uses the same camera as the rest of the fleet eases picture matching.

As already noted, slow-motion cameras are a common requirement. Very high-speed cameras tend to be specified only for individual programs and are most commonly rented in as required. Super slow-motion cameras — which record twice or three times the normal frame rate, allowing smooth replays at lower speeds — are often selected as part of the normal camera complement. They require a specialist server in the truck — or in a separate recording vehicle — which captures the high-speed output and reformats it for slow-motion replay.

Another application for the onboard production server is to play in preprepared motion graphics sequences; mark the difference between live action, replays and comment in sport; or punctuate coverage of live entertainment events. The server needs to be able to link channels to deliver key and fill (four channels for left and right key and fill in 3-D), and ideally the sequences should be loaded as files from a memory device to minimize setup time.

The choice of live graphics device may be determined by the production team, which will have preferences, not to mention prepared content. This is another area where flexibility is critical, allowing devices to be removed and replaced as required.


The production switcher is the heart of any OB unit, and the requirements of big, live productions have driven developments in technology. Four M/E groups or more is a common requirement, with very large numbers of inputs. Multiple outputs are also a common expectation, with a single truck providing different domestic and international outputs. Other applications are to feed in-stadium screens or on-set displays.

Very complex productions will have a second production control room, either in the same truck or externally, but for many jobs it will all need to be switched from the main mixer. This calls for power and flexibility, and the ability to plan setups in advance and download them quickly.

A growing trend is for the switcher to become the hub of the video production, with other equipment triggered from it. The motion graphics sequences on a media server, for example, could be called up from a production switcher, and then cued simply by taking the source.

In productions with a large number of sources, it is likely that there will be a need to reconfigure the switcher during the production. A football or rugby match will need the key pitch cameras and slow-motion replay sources under the operator's hand during the play, but a different layout of cameras and sources during the build-up and post-match analysis. Having a tight link between the production switcher and the main routing switcher makes this a reliable one-button changeover, which in turn makes for a slicker and more secure production.


While most of the new challenges of late have been in getting more equipment into the vehicle, at least new monitoring technology reduces the space required. Flat-screen displays are now virtually universal throughout the truck, with graded LCD displays good enough for camera shading.

The one place where a CRT monitor is still often seen, ironically, is in the audio area. There is a requirement to check lip sync, which is normally the responsibility of the sound supervisor, and taking out of the equation the delay in the display by using a CRT gives a greater level of confidence.

The need to maintain perfect audio and video synchronization end to end is one of the most critical technical elements of the system design, and again it can affect and be affected by changes in other areas. A decision to put a large audio console into the truck (rather than rent in a separate sound mixing vehicle when required) means that the operator and designer have to agree whether to accept the weight of 80 or 100 screened pairs from the tailboard to the audio console, or to save precious kilos.

These are just some of the technical and operational requirements to consider. Once these decisions are made, the OB designer then has to go to work on the detailed equipment layouts. Beyond the obvious space and weight constraint is the need to balance the load evenly over the whole of the vehicle, both on the road and when parked and operational.

It is always possible to modify the vehicle to accommodate some degree of uneven weight distribution, but it adds complexity, weight and cost, and potentially reduces the life of the vehicle. Similarly, on location, we would expect to include in the vehicle systems, which quickly and automatically level and secure it before use, but reducing the load on these systems will keep them working through the investment lifecycle.

The final design consideration is the air-conditioning. Cramming a large amount of electronics, and a fair number of people, into a small space makes ventilation a problem. Cold and fast air flows can be driven through the equipment racks, but that does not work so well in the operational areas. Under the pressure of live television, the last thing the director wants is noisy fans or cold draughts.

Special chassis designs, like the Jumbo, help to reach all these goals in a cost-effective way. The main idea of this concept is the use of an extension, which is on the outside of the van. Ordinary OB vans use drawers as extensions, but the Jumbo concept covers the full length of a van. This creates a maximum of internal space and the largest ceiling height for the extension. A trailer with a maximum external height of 4m can reach an internal ceiling height of up to 2.2m.

The complete interior can be used as one single room, or split according to operational needs. No additional walls are required to improve the stability of the van. The whole construction is extremely rigid and stable. It is even not necessary to use extra hydraulic feet for the extension as its stability allows it to be free floating.

All electronic equipment can be concentrated on the fixed side of the truck, therefore reducing the need for cable chains and bridges.

The Jumbo concept leads to a reduced weight of the complete truck, as a single extension needs less parts compared with a double extension. The necessary steel carriers, hydraulic cylinders, pumps, etc., will be needed only once, so a lot of weight can be saved.


A specialist builder of OB vehicles is a valuable partner for the operator specifying a new truck. Anyone can select the major technical equipment; the real differentiators are operational flexibility in the layout, system design to maximize reliability while minimizing weight, and the quality of the construction and facilities to ensure that the staff can create great television and the vehicle remains mobile through its lifetime, delivering a strong return on investment.

Uwe Ritter is head of business development at Grass Valley and Sven Loeffler is special projects engineering manager at Grass Valley.