Very strange Sample & Hold Behavior on image signals

[Pavel_47]

Hello,

Here is video fragment on behavior of my video acquisition setup.

The setup keypoint - image must be available on output on odd iterations (1, 3, 5, ....) and kept previous value on even iterations.

As you can see from video the behavior is completely different

Where is the problem ?

Thanks

[James.M · Accepted solution]

IMAQ probes have always worked a little funny to me. It stems from the fact that the IMAQ wire you are probing is a reference to the image, not the image data itself. So if you go and alter the image earlier in this code here, that could be the flickering you are seeing. That feedback node is storing the IMAQ reference from the previous iteration, so if your code does something with that IMAQ reference from the previous iteration, then it will show up like this.

Try creating two different IMAQ images with different names and switching between those instead of altering your single IMAQ image reference. You can do this simply with IMAQ Copy once you're done with your vision operations. I usually do a Copy when I know I want to display an image, but will be going back and altering the original image during the next iteration.

[Pavel_47]

Yes, it was the case.

With 2 different images it works.

Thanks