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Can frame grabbers survive the digital divide?

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Are frame grabbers on the way out or do they still have a part to play in vision applications? Gemma Simpson assesses the future of the technology.

Frame grabbers have had a rocky few years. As cameras switch over from analogue to digital, more and more standardised interfaces pop up, applications change and technology moves forward to incorporate a frame grabber’s functionality under the hood of the kit it’s meant  to be helping – is there any room left in the machine vision industry for frame grabbers?

But first, let’s clear up the jargon, starting with what a frame grabber is. Frame grabbers generallylet users get images from cameras into the host memory of a computer, and this is done via an interface, which is basically hardware that interfaces with different cameras and provides a standard output that can be used for subsequent image processing.

Frame grabbers come in two flavours, analogue and digital. Analogue frame grabbers accept and process analogue video signals, and can be made up of circuits such as analogue-to-digital convertors and an input signal conditioner to buffer the analogue video input signal and protect downstream circuitry. Digital frame grabbers accept and process digital video streams, including circuits that form a physical interface to the digital video source. Both flavours have memory for storing the acquired image (i.e. a frame buffer) and an interface through which a processor can control the acquisition and accessing of the data.

But there are a variety of camera interface technologies out there. One such interface is Camera Link, which is a serial communication protocol designed for computer vision applications, based on an interface called Channel Link from manufacturing group National Semiconductor. It was designed to standardise scientific and industrial video products including cameras, cables and frame grabbers. A Camera Link interface can be used to operate analogue or digital cameras and to do this, you normally need a frame grabber as a drop-in card inside a PC.

But the standalone frame grabber unit is evolving and for most digital cameras with USB2, IEEE 1394 or GigE interfaces, the grabber is built into the camera. USB2 is a serial bus standard, which means it sends data one bit at one time sequentially (hence the serial part), over a bus, which is a subsystem that transfers data between the camera and the computer. Unlike a point-to-point connection, a bus can logically connect several peripherals over the same set of wires – which is useful for frame grabbers which may need to sort a series of images from a camera, or range of cameras.

But the notion of a frame grabber has become blurred over the years. Originally it was a type of high-performance analogue to digital converter (ADC) to capture the analogue camera signal with a computer interface, such as ISA or PCI.

Today a frame grabber is usually a digital interface of some sort, for example Camera Link, but it could equally well be an IEEE1394 or GigE adapter card.

USB2 or not to be?

These generic interfaces could kill off the original analogue systems, according to the frame grabber providers. Mark Williamson, sales and marketing director of Firstsight Vision, says: ‘The analogue grabber market is reducing and being replaced with generic interfaces and the higher performance interfaces, such as Camera Link and interfaces with FPGA preprocessing, which are still advancing.’

And as the technology advances, Camera Link will continue to dominate the high-end market, as will its yet-unknown successor, until 10GigE has its feet firmly on the ground as Williamson adds: ‘Until 10GigE becomes a reality the higher end market will remain with Camera Link and even a new generation of interface beyond Camera Link will appear.’

But, until that day, GigE is muscling in on the traditional frame grabber market, according to Markus Tarin, president and CEO of movieMED, who says: ‘In the not too distant future I believe we will see GigE applications stealing market share from the traditional frame grabber market.’

And the up-and-coming trends in the frame grabber market are two-fold, as Tarin adds: ‘I would say that two trends have emerged. The first is driven by the relatively recent adaptation of the GigE standard, which has lessened the need for frame grabber-based systems for some applications. Also IEEE-1394 has done its job for applications where there was a need for buspowered cameras as well as relatively short cable runs between the PC and the camera.’

But bandwidth demands have meant frame grabbers have not been left high and dry, as Tarin adds: ‘The second trend is driven by the need for higher bandwidth applications that is currently best served by Camera Link frame grabbers paired with a PCIexpress bus. This technology provides not only higher bandwidth than GigE, but also deterministic behaviour that is sometimes necessary in high-speed applications.’

And GigE and IEEE1394 don’t have all the answers either, which revives the need for frame grabbers, as Williamson adds: ‘With the advent of GigE Vision and IEEE1394 the concept is that users can use commodity interface products. However, the reality is that to get reliable performance with image transfer, many are just not up to the job.’

This makes it difficult to decide whether frame grabbers are on the way out, according to Tarin, who says: ‘There is an inherent limitation to the interface standards that do not require a frame grabber, such as GigE, Firewire and USB2. All of these interfaces are network or bus compatible, meaning that you can connect multiple cameras to the same interface.’

He adds: ‘However, there lies the limitation. In order to be able to share the same bus and in order to avoid data collision, the data transfer needs to include deliberate pauses in order to allow other parties on the same bus to offload their data to the host. This causes an artificially introduced latency or indeterminism. This is a major trade-off for some applications. For this very reason I believe that these two technologies will continue to coexist for quite some time. They distinctively serve different purposes.’

The analogue versus digital debate

So the frame grabber and the interface standards of GigE, Firewire and USB2, could coexist in the immediate future, depending on the application they are being used for. But these standards are all based on digital frame grabber technology, which adds another layer of complexity to the frame grabber layer cake – what if you need to convert from an analogue to digital format?

Analogue systems with frame grabber technology, generally, tend to be older systems, with fewer of the newer frame grabber installations using analogue.

But there are some areas where analogue frame grabbers will continue to be needed, such as in the security industry. Dwayne Crawford, product manager at Matrox Imaging, says: ‘The security industry will continue to use frame grabbers for many years to come. Given the miles of existing analogue cabling and inexpensive analogue cameras, moving to digital technology might not be cost effective. In addition to the cost of the components, labour costs can eat up much of the budget; analogue coaxial cables are installed and serviced by technicians, while IP camera networks are installed by professional IT specialists.’

In fact, the cost-effective card could give analogue an unexpected lifeline, as Crawford adds: ‘Frame grabbers still have a lot of life within the vision market. Analogue is an excellent example of a technology that was initially forecasted to be dead by now, but demand still remains strong for these products, which continue to maintain a large market share. Many OEMs continue to use these older technologies simply because they work well, are well understood and are still very cost effective.’

So could analogue frame grabbers have a revival? After all, wherever there is an analogue camera, a frame grabber is needed as Thomas Ruf, director of research and development at VRmagic, says: ‘As long as there are analogue cameras in use in industrial applications, frame grabbers will have a part in imaging solutions.’

And analogue is not a thing of the past, with new technologies even finding a place for analogue frame grabbers, as Ruf says: ‘Upcoming, more powerful interfaces like the announced specification of USB 3.0 (USB2.0’s successor) would facilitate the use of multiple analogue cameras connected by a frame grabber to a host system.’

But, similar to the digital switchover for televisions, it looks like there could be a cut-off point where analogue cameras will eventually no longer be used, and therefore analogue frame grabbers will become extinct. Ruf adds: 'The simultaneous decrease in prices and improvements in technology of digital cameras will lead to a decline in the use of analogue cameras and frame grabbers. With more manufacturers configuring their digital components according to established interfaces like USB 2.0, Firewire and GigE, it has become much more convenient to connect digital cameras to a PC.'

And matters will only get worse for analogue as Ruf adds: ‘In the understanding of frame grabbers being analogue video converters, the need for the technology will diminish correspondingly to the market penetration of digital cameras. Understanding frame grabber technology as the function of converting raw image data into defined formats or reducing the data load; smart and intelligent camera components will take over the required functions in the long run.’

But as the analogue frame grabbers slowly dwindle, fibre optics will pick up the gauntlet, according to Tarin, who adds: ‘I believe the analogue frame grabbers are on their last run, but still considerably strong. We will probably see a lot more camera manufacturers implement fibre optic interfaces directly into their camera for super-high bandwidth and speed, as well as long connections between camera (sensor) and processing unit.’

Smart cameras and embedded systems

Embedded systems, which are special-purpose computer systems designed to perform one or a few dedicated functions, could also be the final nail in the frame grabber coffin. And smart cameras, which are a type of embedded system , are also elbowing their way into the frame grabber market, as Matrox’s Crawford adds: ‘Frame grabbers are still a very significant part of Matrox Imaging’s business, but we also see that the market is changing and shifting away from traditional frame grabbers to smart cameras, embedded systems and software.’

And this is a trend that fellow frame grabbers providers are noticing, as Mathias Leumann, CEO and president of Leutron Vision says: ‘The dropin frame grabber cards are replaced more and more by the grabbers inside the camera.’

Leutron moved last year from solely providing frame grabbers to offering camera systems too, which proved a successful move for the company with a predicted double-digit growth in profit over the next couple of years. And the company has noticed a move to more embedded systems too as Leumann adds: ‘A good part of the classic grabbers has been transferred into the  cameras. The classic drop-in grabbers are reduced on Camera Link boards and are pushed more and more into the high-end niche markets.’

But embedded offerings can offer certain advantages, as Crawford adds: ‘Outnumbered by PC add-in frame grabbers, embedded frame grabbers when used with embedded systems generally result in a solution far superior in providing overall revision and lifecycle control as well as an increase in ruggedness for harsh environments.’

But embedded systems still have one or two problems, as it is easier to swap and change a frame grabber card and therefore put the latest grabber technology in a computer, than completely rebuild the PC to improve the frame grabber, as Crawford adds: ‘PC add-in frame grabbers are usually more leading-edge than their embedded counterparts. The embedded frame grabber market tends toward being a late technology adopter as opposed to the PC add-in frame grabber.’

Natural selection

So will frame grabbers slowly become another component, imprisoned under the lids of cameras and computers, which the user takes for granted and does not upgrade until they buy a new piece of kit? Probably not, but frame grabbers will need to evolve to keep up with changing machine vision applications and technologies.

First of all, as technologies become more complex, frame grabbers could help lift the load, as Crawford adds: ‘In the future, complementary technologies will evolve bringing larger, multicore CPUs, higher bandwidth memories and interconnects and so too will the imaging applications. Cameras with higher data rates, 3D and multi-spectral images will start to become commonplace, continuing to push buses and processors to the edge. Frame grabbers will continue to be the vehicle to offload and enable these systems to handle the ever increasing data rates and ever complicated processing requirement.’

And Firstsight Vision’s business development manager, Nigel Doe agrees: ‘OEMs will always try to design out frame grabbers in order to reduce system cost and also to decrease the need to remove the lid of the PC. In reality there are a number of high-performance applications where serial bus technology (GigE, Firewire and so on) does not have the bandwidth, control functionality or determinism to provide a successful technology base. Additionally, even the serial bus technologies frequently require an interface card of some sort to be installed within a PC as the motherboard usually has too little hardware resource available.’

And as more ways to grab and analyse images pop up, the old timer could teach the new kids on the machine vision market block a thing or two, as Inder Kohli, product manager at Dalsa, says: ‘Frame grabbers are no longer the only way to bring the image data into the host computer for processing. However, they will have an important role in machine vision applications for quite some time, because they are continuously evolving from a mere point of interface to a highly complex image processing engine.’

Kohli adds: ‘Without any dependency on the host CPU or the operating system, frame grabbers will continue to offer predictable responses and present data in multiple formats to speed image processing applications.’

And users can expect frame grabbers to become more specialised as the cameras using them do too, as Doe adds: ‘In my view the frame grabber market will simply become more specialised to respond to trends in camera design (higher speed, more bit depth) coupled withmarket requirements. The changeover from PCI to PCIe has only just occurred so I would not expect to great changes in the near future.’

So it looks like the frame grabber will always  exist, in some form or another. Whether it is hidden within the camera, or used with a digital machine instead of an analogue camera. Matrox Imaging’s Dwayne Crawford says: ‘10 years ago people were predicting the demise of the frame grabber – it hasn’t happened yet and I cannot see it disappearing from machine vision anytime soon.’

And like a baddie in a horror movie, when you think frame grabbers have been killed off, they could pop up and surprise the machine vision industry again, as Doe adds: ‘Just when you are thinking that frame grabbers have outlived themselves then another application crops up that demands the capability (be that buffering, control, processing, bandwidth or determinism) offered by the frame grabber!’