Best way to extract synchronized data from bag file for deep learning traning

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The question is how similar are the frequencies and offsets of the three message topics? If they're high frequency then you may be able to use the message_filters package to do what you want very easily. You'll probably need the policy based synchronizer

However if say your akerman steering messages are at a much lower frequency than your images and odometry for example, then you may want to interpolate the ackerman messages to the exact time of the image. Or you may need to interpolate both the ackerman and the odometry topics on this way to match the images. This interpolation method is more complicated but will give more precise results.

Which of these you choose will depend on the rate of each of the three topics and how precisely you need them to be aligned in time.