How to use mpdecimate with the same codec as the input file and audio on the output file

I have a 60 fps Pro Res Video File where I want to keep every 4th frame (the others are duplicates, so in reality 15 fps). The audio has to remain identical (not shifted by the transformation) in the output file. It seems mpdecimate should do the trick but keeping the identical quality and audio was not easy.

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