downsample_bag.py

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#!/usr/bin/env python
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# Author: Bhaskara Marthi
#
# Downsample bags

import roslib; roslib.load_manifest('semanticmodel')
import rospy
import rosbag as rb
import optparse as op
import sys

def main():
    parser = op.OptionParser()
    parser.add_option("-t", "--topic", dest="topic")
    parser.add_option("-r", "--rate", dest="rate", type="float")
    parser.add_option("-v", action="store_true", dest="verbose", default=False)
    options, args = parser.parse_args()

    ds_topic = options.topic
    assert options.rate > 0
    d = 1/options.rate
    if not ds_topic.startswith('/'):
        ds_topic = '/'+ds_topic
        

    inbag = args[0]
    last = None
    last_print = None
    t0 = None
    with rb.Bag(args[1], 'w') as outbag:
        for topic, msg, time in rb.Bag(inbag).read_messages(raw=True):
            store = True
            ts = time.to_sec()
            if not t0:
                t0 = ts
            if not last_print or last_print < ts-1:
                print("Time: {0}".format(ts-t0))
                last_print = ts
            if topic == ds_topic:
                if last and last>ts-d:
                    store = False
                    if options.verbose:
                        print("Ignoring message at ", ts)
                else:
                    last = ts
                    if options.verbose:
                        print("Storing message at ", last)
            if store:
                outbag.write(topic, msg, t=time, raw=True)
                if options.verbose:
                    print("Stored message on {0} for time {1}".format(topic, time))
            
        
        
        
    
    


if __name__ == "__main__":
    main()