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ApproximateTimeSynchronizer publishes in_sync topics through the callback?

asked 2021-11-12 09:28:43 -0500

Ifx13 gravatar image

Hello everyone.

I am trying to synchronize topics with the use of message_filters and ApproximateTimeSynchronizer. I subscribe to the topics that I want to synchronize but when I examine them they don't seem to have the same timestamps. I think I am missing something.

My first impression was that ApproximateTimeSynchronizer just receives data through the subscribers and then republishes them with shared timestamps. But now I think that the Synchronizer just takes in data from the subscribers and filters them without republishing them and IF I wanted to republish them with shared timestamps or whatever then I should do that through the callback.

I would really like some feedback on how to work with this, thanks in advance!

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answered 2021-11-14 07:58:31 -0500

Mike Scheutzow gravatar image

I see a very nice description of the operation at: http://wiki.ros.org/message_filters/A...

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It is a very nice description indeed, but my misunderstanding was not about the selection of the topics that are considered to be "in_sync" but what actually happens after the approximately synchronized messages are selected.

To be more precise after the messages pass from the "message_filters" I thought that they are going to share the same timestamps but that is not the case, it simply dismisses the non synchronized messages by selecting only the approximately synchronized and those can finally be stored, republished, edited.

Anyway thanks for the tip. I think it's half the answer and it is worth noting my previous paragraph in case anybody has the same misunderstanding as me.

Ifx13 gravatar image Ifx13  ( 2021-12-15 03:19:20 -0500 )edit

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Asked: 2021-11-12 09:28:43 -0500

Seen: 50 times

Last updated: Nov 14 '21