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

[Tim Field]

Gregory,

You can export multiple bags to CSV at once using rxbag.  Just pass all the
bag filenames on the command-line, e.g. rxbag *.bag.

Tim

On Thu, Aug 19, 2010 at 11:55 PM, Gregory <hitzgreg at gmail.com> wrote:

>  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 at 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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>>
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