extract.py 文件源码

def skip_from_launch(cap, time):
    """
    Move the capture to T+time (time can be negative) and returns the frame index.
    :param cap: OpenCV capture
    :param time: delta time from launch to skip to
    :return: index of requested frame
    """
    number_of_frames = int(cap.get(cv2.CAP_PROP_FPS) * time) + skip_to_launch(cap)

    number_of_frames = max(number_of_frames, 0)
    number_of_frames = min(number_of_frames, cap.get(cv2.CAP_PROP_FRAME_COUNT))

    cap.set(cv2.CAP_PROP_POS_FRAMES, number_of_frames)

    return number_of_frames