The main problem is that playing a bag files in conjunction with tf is problematic. Tf messages arent't synchronized with the current rosTime. Several alternatives has been proposed but apparently they don't work (at least not for me in python). See http://answers.ros.org/question/1114/waitfortransform-use_sim_time-python and see also http://ros-users.122217.n3.nabble.com/tf-use-sim-time-clock-and-bag-files-td1305066.html
AFAIK this problem is still not solved for tf in python. I think it would be possible if the TransformListener::subscription_callback were public. Am I right? tf::tfMessage's could be retrieved from bag and pushed manually using this method and the Bag API (see below a pythonic code - pytf.cpp modifications also needed):
bag = rosbag.Bag(bag_file)
listener = tf.TransformListener()
for topic, msg, t in bag.read_messages(topics=['/tf']):
listener.subscription_callback(msg)
To reproduce bags with tf messages are very interesting specially in geometric learning problems where bags files with transform information can be used as training database (this is my case).
Until now I'm using this solution to simulate tf in a bag messages at the current time(though I don't like it so much):
import roslib
roslib.load_manifest('tf')
import rospy
import tf
rospy.init_node("tf_restamper")
tfpublisher= rospy.Publisher("tf",tf.msg.tfMessage)
def tfcallback(tfmessage):
for transf in tfmessage.transforms:
transf.header.stamp=rospy.Time.now()
tfpublisher.publish(tfmessage)
tfproxy = rospy.Subscriber("tf_old",tf.msg.tfMessage,tfcallback)
rospy.spin()
Originally posted by Pablo Iñigo Blasco with karma: 2982 on 2011-10-17
This answer was ACCEPTED on the original site
Post score: 5
Original comments
Comment by mkillpack on 2012-02-25:
It seems like some of the timing issues can be dealt with by setting the /use_sim_time parameter to true (use --clock option for rosbag play). However, this doesn't work to play/look at more than one bag file in a single process. When the time starts over for the 2nd bag file, tf freaks out.
