convert image stream received from ros subscribe topic straight to video with ffmpeg

Question

What i want to do is generate a video file(mp4 or mkv format) with ffmpeg from the receiving frames simultaneously without saving images on storage. Attached below is my python ROS subscriber code.

import cv2
from cv_bridge import CvBridge
import rospy
from sensor_msgs.msg import Image
import numpy as np


def callback(data):
    # Used to convert between ROS and OpenCV images
    br = CvBridge()

    # Output debugging information to the terminal
    rospy.loginfo("receiving video frame")
    # Convert ROS Image message to OpenCV image
    current_frame = br.imgmsg_to_cv2(data)

    cv2.imshow("camera", current_frame)

    cv2.waitKey(1)


def listener():
    rospy.init_node("video_sub_py", anonymous=True)
    rospy.Subscriber("video_frames", Image, callback)

    rospy.spin()

    cv2.destroyAllWindows()


if __name__ == "__main__":
    listener()