Black stripes or parts of old data in images

Black stripes and segments of previous images from GigE Vision cameras, are both symptoms of transmission problems (missing data / recycled buffers).

These can be caused by many things, e.g. bad cables, unsuitable NIC configuration, an inefficient NIC, or the PC being too slow to cope with a continuous gigabit data stream.

If you've already followed the suggestions given in the getting started guide regarding receive buffers, jumbo packets and interrupt moderation, you can try the following to determine if your PC is fast enough:

  • Set the camera's acquisition frame rate to 1 fps (or send a trigger every second).
  • Go to Transport Layer Control, and unfold the stream channel selector.
  • place the cursor on the Packet Delay value, and click the small button on the right. That will open the Interpacket Delay Calculator.
  • In the calculator, set max fps to 1, and bandwidth % at 95.
  • If necessary, click the Calculate button. Observe the "New Value".
  • Click OK. This will update the packet delay line to the number in "New Value".

Now the average speed of the data stream has been lowered to much less than a gigabit. (Of course, the individual packets are still sent at gigabit speed). The first bullet sets the frame rate. The next 5 bullets adjust the network properties of the camera, to distribute the load over time.

Then you have to:

  • Start Acquisition.
  • Observe if the problem has disappeared or improved.

If the problem has disappeared, you can increase the frame rate by following the steps above, and see at which data rate you run into problems again.

Tip: Using a larger packet size will reduce the number of interrupts on your PC.

It is always recommended to use the GigE Vision filter driver. If you are using the JAI SDK with a socket driver, you may experience a loss of the first two network packets of each image.

 

Tags :  Image data, corrupt images, old data

Products : GigE Vision cameras

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