Play a bag with a step

edit

You're describing subsampling a topic, correct?

If so: I don't believe that is supported right now.

You could post-process your back yourself using the rosbag API. Only keeping 1 out of 3 messages shouldn't be too hard to implement.

Edit:

Yes, i want to record on an other bag, only 1 out of 3 messages that are published from the original bag. can you tell me more about how can I do it ?

write a Python script that does something like the following:

import rosbag

# opening hard-coded filenames here, but you could obviously make this
# a command line option

count = 0
with rosbag.Bag('output.bag', 'w') as outbag:
    for topic, msg, t in rosbag.Bag('input.bag').read_messages():

        # drop only messages on 'your_topic'
        if topic == "/your_topic":
            # here we drop every 2 out of 3 messages
            if (count % 3 == 0):
                outbag.write(topic, msg, t)

        else:
            outbag.write(topic, msg, t)

        count += 1

This is essentially example 1 combined with example 5.

I haven't checked this, so it could be that you'd need to tweak this a bit or make some corrections.