A better solution would be to divorce the rate of rotation from your frame-rate.
For example, you want to rotate 360 degrees in 6 seconds, that's a rate of 60 degrees per second. Measure the time difference in seconds between calls to your rendering code, multiply it be the rotation-per-second figure and add that to the rotation angle.
This'll give you a consistent speed of rotation, no matter what the frame-rate is.
But I still wouldn't know the actual frame rate and frame timings. My aim is to use real time captured data to control the viewpoint.
It is important to know 1) the latency between capture and display time, 2) any variations in this latency, 3) what the frame rate is and if any frames are dropped.