def get_first_annotated_frame_index(filename):
  """ determines the frame index of the first annotated frame.
 
  It is based on the timestamps file provided with the annotations of
  particular recording.

  This timestamps file provides both the frame index and corresponding timestamp
  for all images that have been manually annotated in the recording.

  Note that if the file does not exists, this function considers that
  the frame index of the first annotated frame is 0 at time 0
  
  Parameters
  ----------
  filename: str
    The file with annotations timestamps. 

  Returns
  -------
  list of tuples:
    List of (frame_index, timestamp) for annotated frames in the sequence.
  int:
    Status of the process (-1 meaning failure)

  """
  status = 0 
  try:
    f = open(filename, 'r')
    first_line = f.readline().rstrip()
    first_line = first_line.split(' ')
    indices = (int(first_line[0]), int(first_line[1]))
    f.close()
  except IOError:
    status = -1 
    indices = (0, 0)
  return indices, status