Advanced Imaging


Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

FireWire Makes a Move

In the first of a series on data path we examine how IEEE 1394 security imaging designs deliver significant benefits in efficiency and cost savings
1394 Trade Association
Pixel Velocity implements its Pixel Video Fusion System using a FireWire network over optical fibers or CAT 6 UTP. The FireWire network connects fixed field of view high-definition pixel cameras to a video recording server, which is then connected to the structure’s IP network.
FireWire’s isochronous mechanism allows a camera to source many distinct video streams at the same time. This system’s cameras can source up to eight image streams at a time, with resolutions from uncompressed 1920x1080 to compressed 640x480 with the default setting to output two streams.
Nine different agencies provide game-day security at the 107,000-seat University of Michigan football stadium. The system, with 31 high-def cameras, connects to and utilizes the existing network used by stadium operations and the media. It monitors the parking lots, entrances and exits, and interior seating, has face-recognition resolution for all seats and license plate resolution in the parking lots.
A field-of-view comparison using Pixel Velocity’s camera system. The simplification to fixed field of view allows the system to be paced by the speed of computing, not the speed of mechanical pan, tilt, and zoom motors.

By Burke Henehan
1394 Trade Association

We have all seen them on the TV news, a crime committed on camera, but the analog camera resolution is so poor the police can’t identify the perpetrator and are hoping some member of the public can help. Analog cameras have their place, at least as intimidation, so the signs saying “Premises under Video Surveillance” are not inaccurate.

But as for audio and TV, digital is the path to better performance and more capability in security imaging. The analog to digital (A/D) conversion is done inside the camera close to the CCD/CMOS imaging sensor, retaining the most quality and least noise. The image then is transmitted digitally making it highly tolerant of noisy environments. Since the A/D conversion is done in the camera it does not suffer the distortion that tens of meters of cable or the electrically noisy computer can inject to distort the analog image. This all increases the capabilities of the security system.

So what are the improvements when a digital surveillance system is used? It depends on the transport system and protocols. Internet Protocol (IP) video-based cameras can interface directly into an existing network, but can easily saturate the available bandwidth if used at higher resolution than analog cameras. If the update rate is lowered to reduce the bandwidth requirements the video updates so slowly that important details easily can be missed. But a historically short-range technology, FireWire, is being used in a new way to solve many of these problems and reduce costs at the same time. Originally used for video peripherals, external mass storage and the like for PCs and Macs, the Institute of Electrical and Electronics Engineers standard number 1394-2008 (Apple’s FireWire) implementation now is being widely implemented in industrial applications. (Note: 1394-2008 is a one-document consolidation of 1394-1995, 1394a, 1394b and their errata.) The key enabling technology addition was transport across long haul cables, namely UTP5/6, coax, and fiber, up to 100m at up to 800Mbps. While this enhancement enabled large-scale security imaging, many of FireWire’s other features make it the eager choice of digital security systems. This is my Top 10 list:

1. IEEE 1394-2008 allows individual cable runs of up to 100m. This includes use of the nominal shielded twisted pair cables (STP), unshielded twisted pair cables (UTP), coaxial cables (co-ax), plastic optical fiber (POF), and glass optical fiber (GOF). STP has been the standard cable since the beginning of FireWire. It is very mechanically and electrically robust with excellent transmission characteristics and resistance to electromagnetic interference. UTP is the lowest cost and can be used out to 100m runs, and may already be in place to support a previous control path to an analog camera installation. But UTP also is more susceptible to electromagnetic interference in industrial or high EMI conditions (such as airport radar). Coax cables are a well-known and well-shielded medium and also may already be in place from a previous analog installation. The optical cables are the most immune from EMI/ESD issues. POF is cheaper, but has limitations on distance and data rate depending on the fiber optic transceivers selected. GOF is the premium medium; its speed allows the maximum FireWire throughput, longest range (2km), it is EMC/ESD/EMI immune, non-sparking, and non-corrosive. There is even work under way in the 1394 Trade Association to standardize an existing implementation that uses Gigabit Ethernet physical layer transceivers and cables to connect two 800 Mbps FireWire nodes.

2. FireWire is able to carry real-time video (1394 isochronous), control data (1394 asynchronous), and power over a single cable. Analog cameras can require a two- wire cable for power (hot and ground return), another cable for analog video data (coax), and another cable for digital control data (UTP). The fewer the cables the lower the material and installation costs and the shorter the schedule.

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