set input and output video paths

input_path = "input_video1.mp4" output_path = "output_video123.mp4"

open input video

cap = cv2.VideoCapture(input_path)

get input video properties

fps = cap.get(cv2.CAP_PROP_FPS) width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)) height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

set output video properties

fourcc = cv2.VideoWriter_fourcc(*'mp4v') out = cv2.VideoWriter(output_path, fourcc, fps, (width, height))

read and write every 4th frame

frame_count = 0 while cap.isOpened(): ret, frame = cap.read() if not ret: break

if frame_count % 4 == 0:
    out.write(frame)

frame_count += 1

cap.release() out.release() cv2.destroyAllWindows()