Re: [ros-users] rostopic echo -p -b --> Time stamp problem

Hi Tim,

I didn't know that it is possible to generate csv's using rxbag. So
thanks for the hint. But I have more than just one bag file, which
means that this solution becomes quite inefficient.

Using Ken's solution I can use a script, which speeds things up a lot.

Gregory


Tim Field wrote:


Gregory,


You can export bags to CSV with rxbag.  rxbag will export the recorded
time, not the header time.



1. run rxbag bagfile.bag
2. right-click the timeline and select View (by Topic) > topic1 > Plot
3. expand the message tree to display the fields you wish to
export
4. double-click each field to export
5. right-click the plot and select Export to CSV... > All
(or Every Xth message if you want to sample)
6. type topic1.txt and click Save
7. repeat steps 2-6 for topic2



Let me know if you run into any problems.


Tim

On Thu, Aug 19, 2010 at 7:05 AM, Gregory <hitzgreg@gmail.com>
wrote:

Hi,

I have a .bag file that contains different types of messages. When the
file was recorded some of them were
generated by a running node and others were published via 'rosbag play'
from an older bag file, so they have a time stamp from the past (like
two weeks ago).

Ok, so I tried to use:
   
    rostopic echo -p -b bagfile.bag /topic1 > topic1.txt
    rostopic echo -p -b bagfile.bag /topci2 > topic2.txt


to generate files that I can easily read from a matlab script which I
use to analyze the data. However the 'time' field in the text files is
equal to the 'header.stamp' field for all messages. So when I compare
topic1.txt and topic2.txt there is a two week offset not only between
the 'header.stamp' but also between the 'time' fields. Shouldn't 'time'
tell me when the message was recorded rather than what it's timestamp
is?

When I play the bag file all the messages are published and there's no
offset.

Is this a bug in rostopic.py? Or have I completely misunderstood
something?

I use cturtle. OS is Ubuntu 9.10. rostopic.py is at revision 10000.


Thanks in advance!

Gregory





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