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2011-09-03 04:49:57 -0500 commented answer Sequential number does NOT increase in rosbag
Thanks Ken, so.. I really don't know what the possible reasons could be. I will try to use static /tf instead of the /erratic_player today and see if it works.
2011-09-03 04:42:08 -0500 commented question Sequential number does NOT increase in rosbag
Lorenz, each time I used 'rosbag play' I always put the '--clock' after the 'play' as you suggested. The '/use_sim_time' was also set to be true. Actually, I used the same method to run the bag downloaded from the tutorial, and it just worked perfect well.
2011-09-03 04:36:40 -0500 commented question Sequential number does NOT increase in rosbag
Eric, I did set the notifier to DEBUG, and that where the two MessageFilters come from.
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2011-09-02 14:55:03 -0500 asked a question Sequential number does NOT increase in rosbag

Hi,

I am using an Erratic robot equipped with a Hokuyo laser sensor. The first thing I want to do is to get a map by gmapping. I did it in this way:

** Open a few terminals, set the simulated time and then start roscore

** roslaunch erratic_player erratic_base.launch

** rosrun hokuyo_node hokuyo_node

** rosrun erratic_teleop erratic_keyboard_teleop

** rosbag record -O mylaserdata /scan /tf

After the recording finished, I close all of the above except roscore, start the gmapping, and then play the bag by:

** rosbag play --clock mylaserdata.bag

I got nothing but a warning:

warning: [1315017585.310852253, 1315016815.179267613]: MessageFilter [target=/odom ]: Dropped 100.00% of messages so far. Please turn the [ros.gmapping.message_notifier] rosconsole logger to DEBUG for more information.

I checked by the rxconsole, and found something like the following repeatedly.

MessageFilter [target=/odom ]: Added message in frame /base_laser at time 1315016811.038, count now 5

MessageFilter [target=/odom ]: Removed oldest message because buffer is full, count now 5 (frame_id=/base_laser, stamp=1315016810.938059)

I believe there are some reason making the new-coming range information not instantly accepted. So I checked the messages from topics of /tf and /scan. I compared them with the messages from the downloaded bag, and found the "seq" number from /tf does not increase at all: always 0. I guess the reason that the laser readings are over buffered is just this number not increasing.

I am new to the ROS community. Could anyone kindly tell me how to force the "seq" number growing?

Thanks in advance.

Shiqi Zhang