'Return an offset, byte 2-tuple for the next byte in *stream* that is
not \'ÿ\', starting with the byte at offset *start*. If the byte at
offset *start* is not \'ÿ\', *start* and the returned *offset* will
be the same.'

def _next_non_ff_byte(self, start):

    self._stream.seek(start)
    byte_ = self._read_byte()
    while (byte_ == '\xff'):
        byte_ = self._read_byte()
    offset_of_non_ff_byte = (self._stream.tell() - 1)
    return (offset_of_non_ff_byte, byte_)
