Q:

what methods of SampleBuffer do I must use for measurement of frame rate? 

I work with AvFoundation.  I need to measure accurately frame rate from ios camera.  
Algoritm: 
Frame rate = 1/(time(f2)-time(f1))  = __  (frame per second);
Where time(f2) – it's time when come second frame, and (f1) – it's time of first frame.  
How do it with using sampleBuffer?     

A:

You need to call CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
Something like this (in swift, a little awkward because I couldn't find a CMTime 1/x):
let delta = CMTimeSubtract(CMSampleBufferGetPresentationTimeStamp(buf2), CMSampleBufferGetPresentationTimeStamp(buf1))

// awkward 1/x, beware that delta.value may overflow as a timescale
// what's the right way? 
let frameRate = CMTime(value: CMTimeValue(delta.timescale), timescale: CMTimeScale(delta.value))

// maybe you want floating point instead of CMTime:
let frameRateAsFloat64 = CMTimeGetSeconds(frameRate)

