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Can a Virtual Matrix Switch Really Replace an Analog Switch?
The virtual matrix switch continues its full frontal assault on the CCTV video matrix switch. Let's take a step back and look at how well this solution replaces its analog predecessor. How well do virtual matrix switches really perform and what are the benefits of these software applications?
A virtual matrix switch uses an IP network to route compressed digital video streams to a monitor for viewing. The source of the video is either an IP or analog camera's signals that are converted by a video server. The compressed video is carried over IP using standard network protocols.
Video monitoring is typically performed using standard PC workstations. A few virtual matrix solutions such as Genetec's Omnicast and Pelco's Endura will support standard CCTV analog monitors by streaming video to network decoders that convert the compressed video stream to back to analog signals.
Switching control is implemented with video management software designed to support IP cameras and video servers. The virtual matrix function is usually one part of an overall solution for video recording, playback and monitoring. The software sets up the video stream between the camera source and the destination. Destinations include viewing workstations, hardware decoders and servers for video recording.
The virtual matrix functions will vary by software provider, but most will offer guard tours, PTZ control, instant replay and a set of automatic responses to motion, contact closures and other events. Event notification can include an array of visual indicators and audio alarms that can be directed to a specific operator workstation.
Operator control is typically performed using a PC with software user interface, keyboard and mouse. Some packages support USB keypads that are specifically designed for video surveillance security applications. A limited number of virtual matrix software products (Genetec, Verint, Pelco) can be controlled by legacy CCTV keypads through RS-422/485 interfaces that are converted to IP by video servers.
DEATH OF THE ANALOG SWITCH?
The analog matrix switch has been the heart of most CCTV systems used for live video monitoring. The matrix is a physical electronic switch that connects many camera feeds to fewer video monitors and keyboards for live monitoring and PTZ control. Most switches are proprietary, rack-mounted systems that are located close to the operator control room. Operator control is performed with proprietary CCTV keyboard controls. Automated switching is performed on scheduled camera tours or triggered by events such as contact closures.
Not many manufacturers are continuing to invest significant development resources into new analog switch products and upgrades. Pelco is one of the exceptions. Sources at Pelco report an actual increase in analog matrix sales, perhaps due to the stagnant development efforts of its competitors who are choosing to focus on virtual matrix development.
While doing research for this article, I set out to find a case study where an analog matrix switch was removed and outright replaced by a virtual matrix switch. My interviews with the manufacturers of both matrix switches and video management software didn't turn up much. Instead, I discovered two common trends: (1) existing matrix switch systems are being augmented with virtual matrix software and (2) many new surveillance systems are being implemented as pure IP video systems with no analog switching.
Electronic Technology, Inc of Kansas City specializes in retrofitting matrix systems into the IP world. According to principal Dan Carr, ETI is involved in projects that build virtual matrix systems across multiple independent systems that span 23 cities across Kansas and Missouri. The video originates from legacy switch systems, IP cameras and video servers that monitor traffic systems and perform urban surveillance. Permission to view cameras can be selectively and periodically granted to law enforcement, traffic control, TV news and various municipal organizations. ETI uses Genetec's Omnicast software for video management and reconfigures existing fiber systems to carry IP traffic.
BENEFITS OF A VIRTUAL MATRIX SWITCH
- Reach - The major benefit of the virtual matrix switch is reach. An analog video signal is limited by distance and the physical reach of the cable or fiber infrastructure. By contrast, access and control of virtual matrix switch video is available wherever the network can be reached: wireless, LAN or Internet.
- Security - Access privileges to video and PTZ control priorities are handled by the video management software. Some software packages can import users from existing IT systems. Security is applied by validating user access and control and by encrypting the control messaging that sets up feeds and controls PTZ movement. Some products encrypt the video, although this can impact the frame rate of the video stream.
- Video Quality — The level of video quality with IP video is really a design choice. Attributes like the frame rate (up to 30 fps), resolution (up to Megapixel) and level of compression are highly configurable for most IP cameras. Progressive scan sensors eliminate interlace problems with high motion video. Of course, higher video quality means higher storage and network bandwidth requirements.
- Scale - Analog switches scale by adding physical input or output ports. A virtual matrix switch system will scale by adding the network extensions necessary for either new cameras or monitoring stations. Scale is virtually unlimited, as evidenced by a Genetec Omnicast implementation supporting 8,000 cameras at an airport in Europe.
SYSTEM DESIGN CONSIDERATIONS
Products that support "multi-streaming" allow a single video source to be simultaneously compressed and streamed at different levels of quality. For example, a high quality stream may be used for live video monitoring where a LAN network can be built to support the higher bandwidth. A lower frame rate or resolution stream can be used for viewing over the Internet or to reduce the storage requirements for video recording.
The use of multicasting can significantly reduce the load on the network and IP cameras. Multicasting is a function of the network that can deliver a single video feed to multiple monitors, thereby reducing the bandwidth requirements for applications that have a large number of monitor stations.
At the end of the day, virtual matrix products are priced higher, but offer a reach and flexibility that is not attainable with analog matrix switches.