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the video plays faster than realtime because that's a useful behavior to rapidly work through data.

if you want it to "play" at 1x speed, you'll need to insert some waiting. you can pass such a delay to waitKey() in milliseconds.

you could simply pass in 1000 / cap.get(cv.CAP_PROP_FPS) but that won't account for processing time and your video will play slower than realtime.

that's why you should do the following:

tstart = time.perf_counter() # before the loop
# loop starts...
    pts = cap.get(cv.CAP_PROP_POS_MSEC) # before your cap.read()
    # ... cap.read...
    # ... your processing and imshow()...
    time_left = pts - 1000 * (time.perf_counter() - tstart)
    cv.waitKey(int(max(1, time_left)))

the video plays faster than realtime because that's a useful behavior to rapidly work through data.

if you want it to "play" at 1x speed, you'll need to insert some waiting. you can pass such a delay to waitKey() in milliseconds.

you could simply pass in 1000 / cap.get(cv.CAP_PROP_FPS) but that won't account for processing time and your video will play slower than realtime.

that's why you should do the following:

# ... open capture...
tstart = time.perf_counter() # before the loop
# in seconds
# ... loop starts...
    pts = cap.get(cv.CAP_PROP_POS_MSEC) # before your cap.read()
    # ... cap.read...
in milliseconds
    # ... cap.read()...
    # ... your processing and imshow()...
    time_left = pts - 1000 * (time.perf_counter() - tstart)
tstart) # in milliseconds
    cv.waitKey(int(max(1, time_left)))