如何使用Detectron2将经过训练的模型结果绘制在视频上？

import cv2
from detectron2 import model_zoo
from detectron2.engine import DefaultPredictor
from detectron2.utils.visualizer import Visualizer
from detectron2.data import MetadataCatalog

# 加载模型
model = model_zoo.get("COCO-Detection/faster_rcnn_R_50_FPN_3x.yaml")
predictor = DefaultPredictor(model)

# 打开视频文件
video = cv2.VideoCapture("input_video.mp4")

while True:
    ret, frame = video.read()
    if not ret:
        break

    # 对每一帧进行推理
    outputs = predictor(frame)

    # 绘制结果
    v = Visualizer(frame[:, :, ::-1], MetadataCatalog.get(model.cfg.DATASETS.TRAIN[0]), scale=1.2)
    v = v.draw_instance_predictions(outputs["instances"].to("cpu"))
    result = v.get_image()[:, :, ::-1]

    # 显示结果
    cv2.imshow("Result", result)
    if cv2.waitKey(1) == ord("q"):
        break

video.release()
cv2.destroyAllWindows()