def mjpeg_url(self, channelno=None, typeno=None):
        """
        Return MJPEG streaming url

        Params:
            channelno: integer, the video channel index which starts from 1,
                       default 1 if not specified.

            typeno: the stream type, default 0 if not specified. It can be
                    the following value:

                    0-Main Stream
                    1-Extra Stream 1 (Sub Stream)
                    2-Extra Stream 2 (Sub Stream)
        """
        if channelno is None:
            channelno = 0

        if typeno is None:
            typeno = 1

        cmd = "mjpg/video.cgi?channel={0}&subtype={1}".format(
            channelno, typeno)
        return '{0}{1}'.format(self._base_url, cmd)