Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_filetype”.

  FT_FILETYPE determines the filetype of many EEG/MEG/MRI data files by
  looking at the name, extension and optionally (part of) its contents.
  It tries to determine the global type of file (which usually
  corresponds to the manufacturer, the recording system or to the
  software used to create the file) and the particular subtype (e.g.
  continuous, average).
  Use as
    type = ft_filetype(filename)
    type = ft_filetype(dirname)
  This gives you a descriptive string with the data type, and can be
  used in a switch-statement. The descriptive string that is returned
  usually is something like 'XXX_YYY'/ where XXX refers to the
  manufacturer and YYY to the type of the data.
  Alternatively, use as
    flag = ft_filetype(filename, type)
    flag = ft_filetype(dirname, type)
  This gives you a boolean flag (0 or 1) indicating whether the file
  is of the desired type, and can be used to check whether the
  user-supplied file is what your subsequent code expects.
  Alternatively, use as
    flag = ft_filetype(dirlist, type)
  where the dirlist contains a list of files contained within one
  directory. This gives you a boolean vector indicating for each file
  whether it is of the desired type.
  Most filetypes of the following manufacturers and/or software programs are recognized
   - 4D/BTi
   - AFNI
   - ASA
   - Analyse
   - Analyze/SPM
   - BESA
   - Bioimage Suite (*.mgrid)
   - BrainSuite
   - BrainVisa
   - BrainVision
   - Curry
   - Dataq
   - EDF
   - EEProbe
   - Elektra/Neuromag
   - FreeSurfer
   - Localite
   - MINC
   - Neuralynx
   - Neuroscan
   - Nihon Koden (*.m00)
   - Plexon
   - SR Research Eyelink
   - SensoMotoric Instruments (SMI) *.txt
   - Tobii *.tsv
   - Stanford *.ply
   - Tucker Davis Technology
   - VSM-Medtech/CTF
   - Yokogawa & Ricoh
   - nifti, gifti
   - Nicolet *.e (currently from Natus, formerly Carefusion, Viasys and
                  Taugagreining. Also known as Oxford/Teca/Medelec Valor
                  - Nervus)