mp4转ros bag包

操作方法:
python2 mp4_to_bag.py lane_video.mp4 lane_camera.bag # 执行转化命令
rosbag play -l TLout.bag camera/image_raw:=image_raw0 # 循环播放图片，并重命名成自己需要的话题名

import time, sys, os
from ros import rosbag
import roslib, rospy
roslib.load_manifest('sensor_msgs')
from sensor_msgs.msg import Image

from cv_bridge import CvBridge
import cv2

TOPIC = '/wstek/camera0'

def CreateVideoBag(videopath, bagname):
    '''Creates a bag file with a video file'''
    print videopath
    print bagname
    bag = rosbag.Bag(bagname, 'w')
    cap = cv2.VideoCapture(videopath)
    cb = CvBridge()
    # prop_fps = cap.get(cv2.cv.CV_CAP_PROP_FPS)  
    prop_fps = cap.get(cv2.CAP_PROP_FPS)  
    if prop_fps != prop_fps or prop_fps <= 1e-2:
        print "Warning: can't get FPS. Assuming 24."
        prop_fps = 24
    prop_fps = 24 # 
    print prop_fps
    ret = True
    frame_id = 0
    while(ret):
        ret, frame = cap.read()
        if not ret:
            break
        stamp = rospy.rostime.Time.from_sec(float(frame_id) / prop_fps)
        frame_id += 1
        image = cb.cv2_to_imgmsg(frame, encoding='bgr8')
        image.header.stamp = stamp
        image.header.frame_id = "camera"
        bag.write(TOPIC, image, stamp)
    cap.release()
    bag.close()

if __name__ == "__main__":
    if len( sys.argv ) == 3:
        CreateVideoBag(*sys.argv[1:])
    else:
        print( "Usage: video2bag videofilename bagfilename")