Start reading a video from t1 timestamp until t2 and extract every fn frame

Python
1

Hi,
I’m trying to read a video (60 fps) within a custom range [t_{start} - t_{end}] and since not every timestamp is documented in my data, I need to extract frames every .2 seconds.
For example:
0 is t_{start} and 3.2 is t_{end}, so extract the frames at [t_0, t_{0.2}, ... , t_{3.2}]

I’m fairly new to OpenCV so this is what I had in mind:
after initializing cap with cv2.VideoCapture, i’ll use the CAP_PROP_POS_MSEC flag to initialize my starting time:

cap.set(cv2.CAP_PROP_POS_MSEC, start_time * milliseconds)

Now I didn’t find any flag that corresponds to my end_time so the only “fix” I could think of was something like:

while cap.isOpened() and cap.get(cv2.CAP_PROP_POS_MSEC) <= end_time * milliseconds:
    ret, frame = cap.read()
    ...
    ...
    cap.release()
    break

And for extracting every 0.2 seconds which is every f_{20} frame the final logic will look like this:

FRAME_POS = 0
frames = []
while cap.isOpened() and cap.get(cv2.CAP_PROP_POS_MSEC) <= end_time * milliseconds:
    ret, frame = cap.read()
    if ret:
        frames.append(frame)
        FRAME_POS += 20
        cap.set(cv2.CAP_PROP_POS_FRAMES, FRAME_POS)
    else:
        cap.release()
        break

If this implementation is correct, is there anyway to optimize it with built-in methods/flags?