SONGetExtMarkData

  SONGETEXTMARKDATA returns the timings, marker values and extra data
  for an AdcMark, RealMark or TextMark channel

  Implemented through SONGetExtMarkData.dll

  [npoints, times, markers, extra]=
         SONGETEXTMARKDATA(fh, chan, maxpoints, stime, etime{, filtermask})

             INPUTS: FH = file handle
                     CHAN = channel number 0 to SONMAXCHANS-1
                     MAXPOINTS = Maximum number of data values to return
                                 (up to 32767, if zero this will be set to
                                    32767)
                     STIME  = the start time for the data search
                                    (in clock ticks)
                     ETIME = the end time for teh search
                                     (in clock ticks)
                     FILTERMASK  if present is  a filter mask structure
                                    There will be no filtering if this is
                                    absent.
            OUTPUTS: NPOINTS= number of data points returned
                                or a negative error
                     TIMES = an NPOINT column vector containing the
                                timestamps (in clock ticks)
                     MARKERS = an NPOINT x 4 byte array, with 4 markers
                            for each of the timestamps in TIMES.
                     EXTRA= An X x NPOINT array. The NPOINT columns contain
                             the extra data for each marker. The length of 
                             the columns varies between channels.
                             EXTRA is int16 for ADCMark channels, single 
                                for RealMark and uint8 for TextMark

  Note: If required, cast TextMark EXTRA data to type char in MATLAB 
        If you do not need the EXTRA data, use SONGetMarkData instead

  For error codes, see the CED documentation

  Author:Malcolm Lidierth
  Matlab SON library:
  Copyright © The Author & King's College London 2005-2006