How can I convert a video or sequence of images to a batch file?
I am new to ROS. I need to convert an existing video file or a large number of images that can be merged into a video stream to a file .bag
in ROS. I found this code online: http://answers.ros.org/question/11537/creating-a-bag-file-out-of-a-image-sequence/ but it says it is for calibrating the camera so not sure if it suits my purposes.
Can anyone with a good knowledge of ROS confirm that I can use the code in the link provided for my purposes, or if someone really has the code I'm looking for, could you post it here?
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The following code converts the video file to a bag file inspired by the code in the provided link.
A little reminder:
1) this code depends on cv2 (opencv python)
2) ROS message timestamp is calculated by frame index and fps. fps will be set to 24 if opencv cannot read it from the video.
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 = 'camera/image_raw'
def CreateVideoBag(videopath, bagname):
'''Creates a bag file with a video file'''
bag = rosbag.Bag(bagname, 'w')
cap = cv2.VideoCapture(videopath)
cb = CvBridge()
prop_fps = cap.get(cv2.cv.CV_CAP_PROP_FPS)
if prop_fps != prop_fps or prop_fps <= 1e-2:
print "Warning: can't get FPS. Assuming 24."
prop_fps = 24
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")
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