def _parse_frange_part(frange):
        """
        Internal method: parse a discrete frame range part.

        Args:
            frange (str): single part of a frame range as a string
                (ie "1-100x5")

        Returns:
            tuple: (start, end, modifier, chunk)

        Raises:
            :class:`.ParseException`: if the frame range can
                not be parsed
        """
        match = FRANGE_RE.match(frange)
        if not match:
            msg = 'Could not parse "{0}": did not match {1}'
            raise ParseException(msg.format(frange, FRANGE_RE.pattern))
        start, end, modifier, chunk = match.groups()
        start = int(start)
        end = int(end) if end is not None else start

        if end > start and chunk is not None and int(chunk) < 0:
            msg = 'Could not parse "{0}: chunk can not be negative'
            raise ParseException(msg.format(frange))

        chunk = abs(int(chunk)) if chunk is not None else 1
        # a zero chunk is just plain illogical
        if chunk == 0:
            msg = 'Could not parse "{0}": chunk cannot be 0'
            raise ParseException(msg.format(frange))
        return start, end, modifier, chunk