Considering camera connectivity

The camera cable conundrum for outside broadcast contractors.
Join the dots: Get that camera connected!
Join the dots: Get that camera connected!


Outside broadcast contractors are under constant pressure to make the best use of their assets: including their trucks, cameras, switchers and the rest of the technology.

Yet one of the biggest restrictions on productivity is a seemingly humble part of the system: the camera cable. Cameras must be linked back to the truck and, on some outside broadcasts that can involve laying very long cables indeed.

Camera connectivity is no simple matter. The output of the camera, first of all, is a very high frequency signal. The first colour television cameras were connected over a multi-core cable which was bulky and complex to use, even in studios.

It was actually Grass Valley, working in association with CBS, which developed the triax cable system. The technology won an Emmy and went on to become a global open standard.

As well as the camera output, the triax cable carries other signals, too. Much of the camera’s technical parameters will be adjusted from the CCU in the truck, requiring a data path. There may be a microphone or microphones located at the camera.

There will certainly be two-way talkback between the operator and the truck. In most applications there will be a need for one or two return video feeds to be carried to the camera, to help the operator line up the shot or for the prompter. Finally, there needs to be power to drive the camera and other electronics.

The triax system, then, was a significant technical achievement and, one created with future capabilities built in. Remember it was developed in the era of analogue, standard definition cameras. Since then we have moved to digital transmission and from standard definition to HD, with 1080p HD on the near horizon.

There is no point in buying the best HD cameras if you cannot get the picture back to the truck in pristine condition. Uncompressed HD signals, at 720p or 1080i, require 1.5 gigabits of data per second, which is a very high data rate.

To move to 1080p video, as many engineers aspire, doubles the data rate to 3 Gb/s. Stereoscopic 3D, another important innovation today, uses two conventional HD channels for each “3D camera,” so also needs 3 Gb/s transmission (1.5 Gb/s for each camera in the stereoscopic pair).

To send these high data rates down any cable creates the equivalent of radio frequency signals, and this in turn limits the maximum distance which can be covered without an additional device to recover and regenerate the signal. For fibre this is around 5 km, but thanks to innovative electronics, triax can reach more than 1 km.

So triax systems continued to be developed to meet the challenge of digital HD. These are particularly important, as a lot of established sports venues, such as most of the Premier League football grounds in England, have triax cables permanently installed to the camera positions, helping the OB crews by reducing rigging time and thereby increasing productivity.

At the same time, an alternative transmission solution for digital HD was developed, using fibre. Some vendors have suggested that fibre is inherently superior, largely for marketing purposes. In reality there are benefits on each side.

For triax they include:
• It is pre-installed in a large number of major venues
• Outside broadcast companies have invested in large stocks of triax cables
• It is highly reliable and very rugged, and in an emergency can be repaired on site.

Arguments in favour of fibre include:
• It has had, in the past, greater digital capacity, establishing for example the idea of two return video channels
• It was the first to implement 3 Gb/s 1080p HD video
• It has a greater range, important at big sports events where the trucks are being pushed ever further from the action.

As you will see, there are clear arguments in favour of both triax and fibre. Just as venues were traditionally pre-cabled with triax, now some (although not all) new venues are being fitted out with fibre.

The result is that an outside broadcast contractor either has to choose one transmission format over the other, and therefore be forced to turn down work which it would be ideally suited; or it has to have the capability of working over both triax and fibre, which previously meant a double inventory of cameras and a return to base between jobs for camera transmission systems to be changed over.

This seems an artificial limitation on the outside broadcast industry. Like everything else in broadcasting, the technology should not be a limitation but a spur to creativity. Dictating how a live event should be covered by something as humble as the camera cable is not the correct approach.

This is the thinking behind a new development from Grass Valley; 3G Transmission. Although its name actually comes from the fact that it is the third generation transmission system, it has been developed for the needs of 3 Gb/s signals over any medium.

The same core technology is used whether the connection is over fibre or triax. At the truck end, either can be accepted; the modular nature of the LDK 8000 and LDK 4000 HD cameras means that a fibre or a triax back can be quickly installed without changing anything in the business end of the camera.

Functionality is identical across the platforms, two HD video returns, four stereo audio pairs plus talkback, and data for camera and transmission diagnostics and control and for other applications. As a side benefit, the new 3G transmission system actually extends the length of triax which can now be fed up to a safe maximum of 1500 meters.

Providing the initial in-service testing and feedback was the leading UK-based outside broadcast company NEP Visions, which equipped a 20 camera truck with the system in order to service one of its key sport contracts.

Steve Jenkins of NEP Visions reflected on the initial experience – including a challenging job in the Middle East: “We have contracts with the top broadcasters who are always pushing us for bigger, better technology, as well as delivering consistently high technical quality. 1080p production is certainly in their minds, so when we are planning future investments we have to consider it. The new 3G Triax system from Grass Valley ticks those boxes. We now have trucks which are genuinely 3 Gb/s ready from cameras through the triax to the switcher.

“The extra length over triax helps too. Logistics at venues means we are being pushed further away, and being able to run 1500 metres of triax can save a remote engineering position, which makes the installation faster and more cost effective.

“Although the new 3G Triax system is now busy on sports coverage in a truck, the first outing was rather more challenging: we provided a flyaway kit to the US Air Force base in Qatar in the Gulf, where we covered a women’s football match for the troops last Thanksgiving. We completed the rig, and were concerned with patterning on some of the cameras.

“It turned out that the cameras affected were close to the Patriot missile launchers which were generating a very strong and uncontrolled RF field. Rapid application of aluminium foil solved the problem!

“That exceptional situation aside, it has been a very smooth transition for us. The new transmission system does exactly what Grass Valley promised us it would do, and is now helping us serve our customers more effectively.”

Camera connectivity will always be an important part of our industry. So it is particularly important that the choice of cable should not dictate the rest of the production equipment.

Outside broadcast companies need to understand the challenges and practicalities of camera transmission systems, and work with manufacturers on innovative solutions.

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