Synchronizer and multiple message with same timestamp

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Hi all,

I'm trying to synchronize two topics (/joint and /odom). Until now I've got no problems in performing that synchronization. Now the /joint source is changed and I am unable to perform the synchro.

The problem is this one: the node source of topic /joint publishes, at each time stamp, two different messages, with different seq, but same stamp.

Using the Synchronizer, in the callback I have access only to the second message, since, I think, it considers the second message (same timestamp but higher seq number) the nearest in terms of time. I need to access the first message from the Synchronizer...but I don't know how

hope someone can help me =)

bart