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What may cause video lag?


The cascade port is Gigabit and the total bandwidth is not fully consumed, but why sometimes there is still video lag?

Assume the topology is as below shown. Each switch connects 6 cameras, and each camera costs 10Mb, all 600Mb traffic moves into one direction.


The reason could be below items:

  1. Background traffic
    If you are running video stream and general data together, please check if the general data traffic is over 400Mb and let the total bandwidth over the 1G speed.

    • Enable VLAN: separate the video stream and general traffic, to avoid any interaction
    • Enable QoS: set packet priority and let video stream always be sent in first time.
  2. Camera settings
    Check if your cameras are running VBR(Variable Bit Rate) mode. In the Axis camera, the default setting of bandwidth is VBR (Variable Bit Rate) mode and unlimited bit rate. VBR adjusts the bit rate according to the image complexity, using up more bandwidth for increased activity in the image, and less for lower image activity. However, if there is lots of activities such traffic intersection, the bandwidth consumption will be much higher, and may over 10Mb.

    • Change to CBR (Constant Bit Rate) mode. CBR allows you to set a fixed target bit rate that consumes a predictable amount of bandwidth.

      Video Stream Settings
    • Reduce the frame rate
    • Reduce the video resolution
    • Recalculate the camera bandwidth by using maximum bandwidth
      • To know the maximum bandwidth, you can change you video background or just put your hand in front of the camera, and then check the networking traffic by windows Task Manager.

      Windows Task Manager