how to calculate threshold value in frame difference algorithm

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Ayesha ayub am 18 Aug. 2014

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Kommentiert: Mohammedashraf Shaikh am 6 Apr. 2017

i was studying frame difference algorithms and in every pdf it says find threshold value and didn't mention how can anyone tell me how

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Ayesha ayub am 19 Aug. 2014

for motion detection i am using frame difference algorithm that is current frame-previous frame but this algorithm is comparing the frame difference with a threshold value. i saw a code where they took threshold 25 with no reason why

Image Analyst am 19 Aug. 2014

Because it worked for them. The value that "works" for you may be different, as I said in my Answer below.

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Image Analyst am 18 Aug. 2014

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Subtract the frames. Be sure to cast to double before you do so to avoid clipping values less than zero. You might want to take the absolute value of the difference image. Then pick a threshold however you want. The lower the threshold, the more stuff you will get and the higher the threshold the fewer pixels will be selected. Choose the threshold to get just the pixels you want and no others. Thresholding may not do it - you may have to combine with other methods, like spatial operations that consider neighborhoods around each pixel, or shape, or whatever. It really depends on what you want to find.