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Which digital video interface is best for global security systems?

Posted by Gretchen Alper on Fri, May 29, 2015

Move from analog to digital

To improve the information gathered from situational awareness, long-range observation and designator systems, the big trend is to increase the resolution of the daylight video cameras from VGA to HD and greater for more accurate full motion video content. Higher resolutions allow for an increased field of view (FOV) with equal DRI (detection, recognition, identification) capabilities or increase DRI from further distances.

There are efforts in both the military and other global security areas to move from analog to digital to meet the video intelligence goals and other networking needs.  With digital there is no degradation of data over the interface as with analog there is more noise with longer cables.  The video recording that is enabled with digital allows for distribution over long ranges.

Some legacy systems that have switched to digital used what was available at the time such as those from the broadcast market, i.e. SDI, or from the machine vision market, including Camera Link or GigE Vision. But now the interface has become a limiting factor in supporting the bandwidth of greater resolutions and frame speeds, and there are many high-speed interfaces to choose from.

To determine which video interface would be best for your next daylight camera upgrade, it is a good first step to identify which interface requirements are most important for global security systems. 

Video interface requirements for global security systems

Here is a list of the most typical video interface requirements particular to defense and global security systems:

  • Minimize SWAP-C
    • Number of cables needed for interfacing
    • Size of connectors needed for interfacing
    • Power consumption of interface
    • Cost of cables
  • Long cable lengths and flexible cables for routing throughout vehicles and use with slip rings
  • High reliability
  • Support HD resolution (color) at 60 frames/second
  • Enable various image formats for backwards compatibility
  • Allow for upgrades to greater resolutions in the future

Some additional comments on SWAP-C…the size of the cable driver can also have a big impact on the size of the camera. In addition, power over the interface not only reduces the number of cables but also the number of connectors (which can be large).

Pros and Cons of different interfaces for global security

With those requirements in mind, let’s look at the pros and cons of some different video interfaces. For detailed background information on the different interface standards, see our free ePaper. Or download the official Camera interface comparison from the 3 global Machine Vision organisations, JIIA, EMVA and AIA

Here is a quick overview of the specs:

coaxpress-machine-vision-interface-comparison-gs

 

Camera Link (single cable)

Pros

  • Well-established standard that is reliable for short distance connection
  • Enables various image formats
  • Good for upgrade of camera in existing system using Camera Link
  • Power over the cable is optional

Cons

  • Limited bandwidth (only up to 30 fps possible with full HD color)
  • Does not allow for future upgrades of greater resolutions
  • Short, stiff, expensive cables

 

HD-SDI / 3G-SDI

Pros

  • Well-established interface that is good when standard HDTV is good enough for system
  • Upgrade of camera in existing system that is already using HD-SDI

Cons

  • Does not allow for different image formats or greater resolutions than HD (TV focused)
  • Extra cables for power, communication, triggering etc. are required

 

GigE Vision

Pros

  • Provides a traditional way of setting up video networks
  • Long, flexible, inexpensive cables

Cons

  • Large R45 connector
  • Processing required to pack and unpack video generates additional heat and uncertain latency (reliability issues)
  • Bandwidth limited (no HDTV without compression possible over GigE)
  • Accurate triggering over the cable may be difficult to implement

 

USB3 Vision

Pros

  • Commonly known standard based on consumer interface
  • No frame grabber required (interface card required) 

Cons

  • Large connector and interface driver
  • Maximum throughput unpredictable (chipset, PC motherboard and driver dependent)
  • Sustainable speed is much lower than theoretical limit
  • Unreliable operation with longer cables (>3 m)

 

CoaXPress

Pros

  • One interface standard for systems today and in the future – very high bandwidth capability moving to 12 Gbps per cable
  • One flexible cable solution (includes power over cable): lowest SWAP and Cost
  • One cable interface - EMC/EMI friendly
  • Backward compatibly with 75 Ohm Coaxial cable (when using existing infrastructure like HD-SDI or even analog)
  • Any display format is possible
  • Low latency and stable video transfer, reliable with hardware control through direct memory access

Cons

  • Requires a frame grabber
  • Relatively new standard, not yet well-known in the industry

An overview of the pros and cons:

coaxpress-machine-vision-interface-comparison-gs2

Here are our thoughts – we welcome yours! Please leave us a comment or give us a call with any comments or questions.

Topics: Interface Technology

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