SONWriteExtMarkBlock

  SONWRITEEXTMARKBLOCK writes data to a marker channel

  Calls gatewaySONWriteMarkBlock.dll after transposing EXTRA

  RET=SONWRITEEXTMARKBLOCK(FH, CHAN, TIMESTAMPS, MARKERS, EXTRA, COUNT)
  INPUTS: FH the SON file handle
          CHAN the target channel
          TIMESTAMPS a vector of int32 timestamps for the markers
                    which should be at least COUNT in length
          MARKERS the 4xCOUNT array of uint8 marker values, one set of
                    4 for each timestamp
          EXTRA the array of extra data, int16, single or text
          COUNT the number of marker items to write to the buffer

  Returns zero or a negative error code.

  For efficient use of disc space, COUNT should be  a multiple of 
  (BUFSIZE bytes - 20)/4 , where BUFSIZE is supplied in a prior call to
  SONSETWAVECHAN, SONSETREALMARKCHAN or SONSETTEXTMARKCHAN
  (20 is the size of the block header on disc - see CED documentation)

  See also SONSETWAVECHAN, SONSETREALMARKCHAN, SONSETTEXTMARKCHAN, SONWRITEMARKBLOCK

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