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ROSSerializationException while publishing PointCloud2 Message

asked 2013-04-29 22:34:06 -0500

Josch gravatar image

updated 2014-04-20 14:06:46 -0500

ngrennan gravatar image

Hello everyone,

when my node is publishing a PointCloud2 message I get the following error:

Traceback (most recent call last):
  File "/home/rosuser/ros_workspace/src/udp_83b_adapter_eclipse_python/src/", line 141, in <module>
  File "/home/rosuser/ros_workspace/src/udp_83b_adapter_eclipse_python/src/", line 137, in init
  File "/home/rosuser/ros_workspace/src/udp_83b_adapter_eclipse_python/src/", line 43, in receive
  File "/home/rosuser/ros_workspace/src/udp_83b_adapter_eclipse_python/src/", line 128, in sonarToPointfield
  File "/opt/ros/groovy/lib/python2.7/dist-packages/rospy/", line 801, in publish
    raise ROSSerializationException(str(e))
rospy.exceptions.ROSSerializationException: field fields[].offset must be unsigned integer type

The message is completely generated by my python script. Here is the fields declaration and initialization:

    #  Create 4 PointFields as channel description
    msg_pf1 = smsgs.PointField() = np.str('x')
    msg_pf1.offset = np.uint32(0)
    msg_pf1.datatype = np.uint8(7)
    msg_pf1.count = np.uint32(1)

    msg_pf2 = smsgs.PointField() = np.str('y')
    msg_pf2.offset = np.uint32(4)
    msg_pf2.datatype = np.uint8(7)
    msg_pf2.count = np.uint32(1)

    msg_pf3 = smsgs.PointField() = np.str('z')
    msg_pf3.offset = np.uint32(8)
    msg_pf3.datatype = np.uint8(7)
    msg_pf3.count = np.uint32(1)

    msg_pf4 = smsgs.PointField() = np.str('intensity')
    msg_pf4.offset = np.uint32(12)
    msg_pf4.datatype = np.uint8(2)
    msg_pf4.count = np.uint32(1)

And somewhere later in the code:

    msg_pointcloud2.fields = [msg_pf1, msg_pf2, msg_pf3, msg_pf4]

I'm using python/rospy. Another strange thing: I can run the script. As soon as I try to access the message (e.g. via rostopic echo) the error comes up.

Does anybody have a idea why this is happening? What can I try to debug?

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1 Answer

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answered 2013-04-29 23:29:56 -0500

updated 2013-04-29 23:36:38 -0500

You probably shouldn't use numpy types, but native data types. The offsets field is supposed to be a native python long instead of numpy.uint32. Instead of:

msg_pf1.offset = np.uint32(0)

just write:

msg_pf1.offset = 0

... and so on for all other fields.

Regarding your other comment:

I'm using python/rospy. Another strange thing: I can run the script. As soon as I try to access the message (e.g. via rostopic echo) the error comes up.

This is probably because the serialization code isn't called until there is a subscriber to the topic.

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This was too easy to come in my mind :-D. Thank you!

Another question: When python asks for a unsiged int list, what do I have to give it? An easy list filled with integers is not correct, unfortunately.

Josch gravatar image Josch  ( 2013-04-30 00:29:56 -0500 )edit

Are you sure that a simple list of integers (like [1, 2, 3, 4]) doesn't work? I'm 99% sure it works.

Martin Günther gravatar image Martin Günther  ( 2013-04-30 01:16:56 -0500 )edit

Good point. They were numpy datatypes. I changed them to usual types now (float, float, float, int). Unfortunately python still says: field data[] must be unsigned integer type EDIT: Nevermind, another obvious mistake.

Josch gravatar image Josch  ( 2013-04-30 01:57:10 -0500 )edit

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Asked: 2013-04-29 22:34:06 -0500

Seen: 6,746 times

Last updated: Apr 29 '13