-    def construct_video_urls(self, data):
-        # get sid, token
-        def yk_t(s1, s2):
-            ls = list(range(256))
-            t = 0
-            for i in range(256):
-                t = (t + ls[i] + compat_ord(s1[i % len(s1)])) % 256
-                ls[i], ls[t] = ls[t], ls[i]
-            s = bytearray()
-            x, y = 0, 0
-            for i in range(len(s2)):
-                y = (y + 1) % 256
-                x = (x + ls[y]) % 256
-                ls[x], ls[y] = ls[y], ls[x]
-                s.append(compat_ord(s2[i]) ^ ls[(ls[x] + ls[y]) % 256])
-            return bytes(s)
-
-        sid, token = yk_t(
-            b'becaf9be', base64.b64decode(data['security']['encrypt_string'].encode('ascii'))
-        ).decode('ascii').split('_')
-
-        # get oip
-        oip = data['security']['ip']
-
-        fileid_dict = {}
-        for stream in data['stream']:
-            if stream.get('channel_type') == 'tail':
-                continue
-            format = stream.get('stream_type')
-            fileid = stream['stream_fileid']
-            fileid_dict[format] = fileid
-
-        def get_fileid(format, n):
-            number = hex(int(str(n), 10))[2:].upper()
-            if len(number) == 1:
-                number = '0' + number
-            streamfileids = fileid_dict[format]
-            fileid = streamfileids[0:8] + number + streamfileids[10:]
-            return fileid
-
-        # get ep
-        def generate_ep(format, n):
-            fileid = get_fileid(format, n)
-            ep_t = yk_t(
-                b'bf7e5f01',
-                ('%s_%s_%s' % (sid, fileid, token)).encode('ascii')
-            )
-            ep = base64.b64encode(ep_t).decode('ascii')
-            return ep
-
-        # generate video_urls
-        video_urls_dict = {}
-        for stream in data['stream']:
-            if stream.get('channel_type') == 'tail':
-                continue
-            format = stream.get('stream_type')
-            video_urls = []
-            for dt in stream['segs']:
-                n = str(stream['segs'].index(dt))
-                param = {
-                    'K': dt['key'],
-                    'hd': self.get_hd(format),
-                    'myp': 0,
-                    'ypp': 0,
-                    'ctype': 12,
-                    'ev': 1,
-                    'token': token,
-                    'oip': oip,
-                    'ep': generate_ep(format, n)
-                }
-                video_url = \
-                    'http://k.youku.com/player/getFlvPath/' + \
-                    'sid/' + sid + \
-                    '_00' + \
-                    '/st/' + self.parse_ext_l(format) + \
-                    '/fileid/' + get_fileid(format, n) + '?' + \
-                    compat_urllib_parse_urlencode(param)
-                video_urls.append(video_url)
-            video_urls_dict[format] = video_urls
-
-        return video_urls_dict
-