Getting elapsed time from a video at each frame in Python openCV

Question

I have a video file that I'm doing image processing on. However I need the time elapsed at each frame.

So far I have

frames = camera.get(cv2.CAP_PROP_FRAME_COUNT)
fps = camera.get(cv2.CAP_PROP_FPS)
seconds_per_frame = fps/frames
counter = 0

while True:
    //get frame
    counter += seconds_per_frame

Using this code that I have right now is being finicky. It starts off giving me the time for the actual video but then starts being inaccurate. For example it will say that a current frame is at 12 seconds. But when I actually open the video file and go to that frame, its 7 seconds.

How are you guys calculating time when analyzing video?

Answer 1

I can't see your video in order to check, but I suspect you are accumulating floating point errors.

Try using the frame counter and fps to derive elapsed time like this:

elapsed = frameNumber / fps