Using Inter Packet Delay with GigE Cameras

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Using Inter Packet Delay with GigE Cameras

 

pipe_Attention Consider the settings from GigE Vision -> Network Configuration chapter first.

 

Inter Packet Delay is a parameter to control the data rate from cameras. It is important in multi-camera scenarios.

 

With Inter Packet Delay cameras can be slowed down while acquisition by adding delays between the sent packets. Other devices are able to send data then too.

Inter Packet Delay together with Frame Rate settings and Exposure Time is important as soon as you connect multiple cameras to one network port exceeding together the maximum data rate.

Gigabit Ethernet provides 1 Gb/s (Gigabit per second) Bandwith  ~ 100 MB/s (Megabytes per second) assuming an optimal network hardware and configuration.

In such a system you may have to limit the bandwidth of the cameras by setting the frame rate and the Inter Packet Delay.

 

Tune and Test the Inter Packet Delay

 
- Calculate the max. Frame Rate for each camera considering the needed bandwidth:

Bandwidth = Resolution x Bytes per pixel x FrameRate x Number of cameras

which is for the example below using 3 cameras :  100 MB/s = (1936x1216) x 1 x Frame Rate x 3 => max. Frame Rate for each camera ~ 14 fps

 

AcquFrameRate

 

FrameRate

 

- Now with increasing the Inter Packet Delay you can add a delay time between packets/frames send by the cameras and so increase the Frame Rate values to an optimum (e.g.16 fps)

 

InterPacketDelay

 

If the optimum between Inter Packet Delay and Acquisition Frame Rate is determined, the setting has to be saved in the device options.

 

Save Inter Packet Delay

Use the Device Options (Driver Options for the selected device) dialog window in GenICam Browser App-package-settings-icon

 

DeviceOptionsInterPacket

 

 

Inter Packet Delay based on GevSCPD with different camera models

 

Adding a packet delay between packets during transmission is always based on GenICam Transport Layer Control feature GevSCPD but the representation in camera NodeMaps may differ.
In the following there are some examples how to find the feature.

 

AV GigE example :

They have a feature called "BandwidthControlMode" which is set to "StreamBytesPerSecond" by default.

With "StreamBytesPerSecond"  the bandwidth which is used by a camera can be changed directly in bytes per second.

(e.g. 2 cameras -> StreamBytesPerSecond / 2)

 

AVT-SCPD-Screenshot

 

DALSA GigE example :

 

DALSA_PacketDelay

 

JAI GigE example :

 

JAI_StreamChannel