How to select the specific frame with object

Question

I am detecting the object from the live camera through feature detection with svm , and it read every frame from camera while predicting which affect its speed , i just want that it should select the frame which contain the object and ignore other frames which have no object like empty street or standing car's , it should only detect the moving object

For example , If the object came into camera in 6th frame , it contain into the camera till many frames until it goes out from camera's range , so it should not recount the same object and ignore that frames.

Explanation :

I am detecting the vehicle from video , i want to ignore the empty frames , but how to ignore them ? i only want to check the frames which contain object like vehicle , but if the vehicle is passing from video it take approximately lets assume 5 sec , than it mean same object take 10 frames , so the program count it as 10 vehicles , one from each frame , i want to count it as 1 , because its the one (SAME) vehicle which use 10 frames

My video is already in background subtraction form

I explore two techniques :

1- Entropy ( Frame subtraction )
2- Keyframe extraction

Answer 1

You need an object tracker (many examples can be found on the web for tracking code). Then what you are looking for is the number of tracks. That's your answer.

Answer 2

This question is confusingly worded. What output do you want from this analysis? Here's the stages I see:

1) I assume each frame gives you an (x,y) or null for the position of each object in the frame. Can you do this?

2) If you might get multiple objects in a frame, you have to match them with objects in the previous frame. If this is not a concern, skip to (3). Otherwise, assign an index to each object in the first frame they appear. In subsequent frames, match each object to the index in the previous frame based on (x,y) distance. Clumsy, but it might be good enough.

3) Calculating velocity. Look at the difference in (x,y) between this frame and the last one. Of course, you can't do this on the first frame. Maybe apply a low-pass filter to position to smooth out any jittery motion.

4) Missing objects. This is a hard one. If your question is how to treat empty frames with no object in them, then I feel like you just ignore them. But, if you want to track objects that go missing in the middle of a trajectory (like maybe a ball with motion blur) then that is harder. If this is what you're going for, you might want to do object matching by predicting the next position using position, velocity, and maybe even object characteristics (like a histogram of hues).

I hope this was helpful.