[ros-users] rosbag looping and recording of parameters/services

[Jeremy Leibs]

Dejan,

These are definitely two of the larger problems with rosbag play at
the moment and they keep getting pushed on account of being
non-trivial to solve.

With respect to a), as you mention, the time- and
state-discontinuities make this reasonably complicated.  Could you
provide me with some more information on your particular use-case?
The more I can understand about why it is that people keep requesting
this feature, the better job of addressing it I can do.  At the
moment, I believe your best bet is going to be to have rosbag play
publish the clock for you (using the --clock optioin), and then
between each iteration of the loop, you are going to need to publish
an empty message to the "/reset_time" topic.  There is an open ticket
(https://code.ros.org/trac/ros/ticket/1580) to have rosbag play do
this time-reset for you.  Unfortunately, a search for "reset_time" on
the wiki does not provide any detailed information on what the
ramifications of this time-resetting is going to be on your nodes.  As
long as your nodes are not too stateful, I think this will do the
trick though.

As for b) there is a plan to figure out the appropriate way of logging
parameters (ticket: https://code.ros.org/trac/ros/ticket/2425).  This
will most likely be done by subscribing to a specified parameter list,
and on appropriate invocation of rosbag play, re-setting these
parameters over the course of replaying.  In general you don't want to
play back all of the parameters since any node running on your
played-back data would end up fighting with the player over setting
the parameter.  However, until this support is added, your only option
is to do a "rosparam dump" before you start recording and a "rosparam
load" before you start playing back.  This will only work if you are
recording from nodes that do not do any parameter manipulation, but
that is usually a true statement if you just record from sensors and
you do not reconfigure them over the course of your recording.

--Jeremy



On Thu, Mar 18, 2010 at 5:13 AM, Dejan Pangercic
<dejan.pangercic at gmail.com> wrote:
> Dear rosistas,
> I got following 2 questions:
>
> a)What is the recommendable way of playing rosbag files in a loop? To
> my understanding a simple bash loop  will have issues with the time,
> correct?
>
> b)Is there a plan to incorporate recording of ros parameters and ros
> services? The former would be the only way to log the robot state
> model for isntance.
>
> cheers, D.
> --
> MSc. Dejan Pangercic
> PhD Student/Researcher
> Computer Science IX
> Technische Universität München
> Telephone: +49 (89) 289-17780
> E-Mail: dejan.pangercic at in.tum.de
> WWW: http://ias.cs.tum.edu/people/pangercic
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