Knowledge Base Article
Article Type: How To
Product: License Plate Recognition
Product Version:
Component: Software
Device Brands:
Created: 27-Jun-2012 4:45:28 PM
Last Updated:

How to set the Queue Time feature in ALPR

The Queue Time feature is useful when you have many cameras that are not detecting motion all the time. Using this feature you can, for example, purchase one LPR hardware key but have 10 cameras that each detect motion 5% of the time.

When setting the Queue Time value, you should consider the amount of RAM the current server has.

An example calculation:

  • Image size: 720 * 480 * 3(3 color bytes) = 1036800 (which is roughly 1 megabyte = 1048576 bytes )
  • RAM queue speed: 1Megabyte * 10 fps = 10 Megabytes / per second
  • Queue time of 120 seconds will result in maximum accumulation of 120*10 = 1200 Megabytes
  • If a server has only 4 GB of RAM, customer can only have 2-3 cameras that are set to maximum queue time of 120 seconds
    • 1200M * 3 cameras = 3600M = 3.6GB
    • Some memory must be left for other processes, so this is a bit high for queue time for this system.
  • If queue time is too high and server does not have enough RAM, camera tracking processes will restart with a Not Enough Memory error and the entire queue for that camera will be lost.
  • If a mask is used for VE410 analytic, the amount of RAM will not be equivalent to full screen resolution. As such you can set Queue Time to a higher value.
  • You can set different Queue times per camera, but total RAM should not exceed 50-70% of RAM on the server.
  • If Queue Time is set to the maxium value all the time, License plates will be shown in live video delayed by amount of queue time. As such, it is best to keep this value fairly low (10-20 seconds is recommended)


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