OpenCV Python cv2.BackgroundSubtractor parameters -

Overview

It does not affect the results of the algorithm change parametes of BackgroundSubtractorMOG is.

I'm Python: 2.7.6 | Anaconda 2.1.0 (64-bit)
OpenCV: '2.4.10'
OS: Windows 7 x 64

The default criteria for algorithm are as follows:

 
 
 Reproductive Problem 
 
 First, create two parameters with different parameters; 
 
  bg1 = cv2.BackgroundSubtractorMOG () bg2 = cv2.BackgroundSubtractorMOG (history = 3, nmixtures = 5, backgroundRatio = 0.0001)  
 
 2 "VideoCaptrue ago "The objects: 
 
  cap = cv2.VideoCapture ( 'video.mp4') cap2 = cv2.VideoCapture ( 'different_video.mp4')  
 
 Test a frame from the first capturing object: frame = cap.read () [1] # get both background foreground masks subtractors: fg1 = bg1.apply (frame) Fg2 = bg2.apply (frame) # both results and Show the difference between the two: cv2.imshow ('window name', np hstack (fg1, fg2, fg1-fg2))) cv2.waitKey (30) < / Code> 

After running that block of code for a few frames, the window first shows the results from the background subtractor, r and the difference between the two and the two are included.

Because both masks are the same, the result of their difference (third pane) is a full black frame:

Then, suddenly change the source of the video (second video capture object): get a frame from the second capturing object: frame = Cap2.read () [1] # Get foreground mask from both background subtractors: fg1 = bg1.apply (frame) fg2 = bg2.apply (frame) # Both the result Program and show the difference between them: cv2.imshow ( 'Window name', NP Acstak ((fg1, fg2, fg1 - fg2))) cv2.waitKey (30)

and After running that block of code of some frames:

Two foreground masks look the same, and this is the reason that the third panel is a complete black frame.

But the last block of code for more than 3 frames after the RU, the results of the second panel should be blackened again ( history = 3 due to bg2 in the manufacture of the object). But both background subtractors keep getting the same results (as shown by the third full black pane).

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option

I have also tried to modify my standards:

< P>

"(for example):

  & gt; bg 2.getInt ('history') 3  < / Pre> 
 
 What I have found is that (when there are some versions of OpenCV) when I call the method   BackgroundSubtractorMOG  object, it's a Setting the default  learningRate  parameter to  0.0 , therefore BackgroundSubtractor is not "learning" New Frame, it just used Sticks to the first frame. 
 
 To avoid this, I have to call the method  apply  with a clear education rate parameter, then it works as before. 
 
 after starting T code: 
 
  bg1 = cv2. background Sbttractor Emoji (hats) = CV 2. Veediokapcr ( 'video.mp4') frame = Cap.read () [1]  
 
 ... instead of: 
 
  fg1 = bg1.apply (frame)  
 
 I should: 
 
  fg1 = bg1.apply (frame, learning rate = 0.001)