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

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