`|____|----|____|----|____|----|____|----| 200 Hz, 5mS period, 2500uS High/2500uS Low at 50%`

|___________________|-------------------| 50 Hz, period 20mS period, 10,000uS High/10,000uS Low at 50%

Code will need to measure offset from 50/50 of 50Hz, and adjust ratio same amount in 200Hz.

This means there will be some lag from input to output change, perhaps 2 or 3 cycles of the 50Hz input. (60mS).

Seems like a straightforward enough task of measurement, calculation, and output using Blink Without Delay.