OpenCV читает и сохраняет видео онлайн

import cv2

cap = cv2.VideoCapture(0)  # 0表示电脑默认的摄像头，如果有多个摄像头可以选择其他索引

save_path = 'output.avi'
fourcc = cv2.VideoWriter_fourcc(*'XVID')
fps = 30.0
frame_width = int(cap.get(3))  # 默认视频帧的宽
frame_height = int(cap.get(4))  # 默认视频帧的高

# cap.set(cv2.CAP_PROP_FRAME_WIDTH, 1280)  # 可以将捕捉到的视频帧的宽设置为1280
# cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)  # 可以将捕捉到的视频帧的高设置为720

out = cv2.VideoWriter(save_path, fourcc, fps, (frame_width, frame_height))

while cap.isOpened():
    ret, frame = cap.read()  # 读取摄像头的帧
    if not ret:
        break

    out.write(frame)  # 将帧写入视频

    cv2.imshow('Frame', frame)  # 显示帧

    if cv2.waitKey(1) & 0xFF == ord('q'):  # 按下'q'键退出循环
        break

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