What are the differences between the old and the new implementation of ‘mtmftt’ in ft_freqanalyis?

Several things have changed in the new implementation of frequency analysis by the new low-level module ‘specest’.

• All ‘mtmfft’ output is now phase-shifted such that any angle from any fourier-coefficient is from the perspective of the oscillation in the data being at its peak at time = 0
• ‘mtmfft’ can now take a cfg.foi input-vector as well, instead of the usual cfg.foilim (backwards compatible)
• In many cases the new implementation will run significantly faster. No increase in memory requirement has been seen so far.