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Tech details about difference question


  • Beta Gold

    @mark 

    Hello all,

    I have a technical question about the difference actor. How does it really work ? And what do its parameters? I get it when I use it. I only see what is different (moving) from its output. But some things are unclear to me. I imagine that the RGB values of each pixel in each frame are subtracted from the values of the following frame. But they seem to have some motion blur too because they tend to stay a little. Am I wrong? And what does threshold does? it looks like it allows white or colour rendering of the non frame pixels only if the difference is above a certain level. How is it calibrated?

    Thanks

    Armando   



  • @armando said:

    I imagine that the RGB values of each pixel in each frame are subtracted from the values of the following frame.

     It's very simple.

    New Frame = ABSOLUTE_VALUE(New Frame RGB - Old Frame RGB)

    There is no blurring of any kind. Anything you're seeing in this regard is probably because the webcam (if you're using one) is slowing down it's frame rate to accomodate the available light. If you were seeing this on a higher quality camera (i.e., a good HD camera and coming in via Blackmagic input) I would be very surprised.

    But if you want a little proof, take a look at this patch which uses a Shapes actor into Difference.

    Best Wishes,
    Mark

    shapes to difference.izz