How to reduce redundant time-series data in MySQL into a function?

i have a question that actually does not fit here very much, but maybe it fits. So, i have data like this: How can i reduce this 3 entries with same values? Sure, i can just delete the other 2, but in time-series data i can not just do this, this would hide the information, that in between the real time 15:19:45 and 15:19:55, the value did not change. So i thought about saving the delta-time and value in a separate table and only save the first entry and mark it, but i dont know if this is the best way to do so.