YoutubeIE: new algo for length 87 (fixes #1105)

Squashed commit from the pull requests #1107, #1109 and #1110.

devscripts/youtube_genalgo.py

@@ -16,7 +16,7 @@ tests = [
      "J:|}][{=+-_)(*&;%$#@>MNBVCXZASDFGH^KLPOIUYTREWQ0987654321mnbvcxzasdfghrklpoiuytej"),
     # 87
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$^&*()_-+={[]}|:;?/>.<",
-     "!?;:|}][{=+-_)(*&^$#@/MNBVCXZASqFGHJKLPOIUYTREWQ0987654321mnbvcxzasdfghjklpoiuytr"),
+     "tyuioplkjhgfdsazxcv<nm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$^&*()_-+={[]}|:;?/>"),
     # 86 - vfl_ymO4Z 2013/06/27
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[|};?/>.<",
      "ertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!/#$%^&*()_-+={[|};?@"),

test/test_youtube_sig.py

@@ -30,7 +30,7 @@ class TestYoutubeSig(unittest.TestCase):
 
     def test_87(self):
         wrong = "qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$^&*()_-+={[]}|:;?/>.<"
-        right = "!?;:|}][{=+-_)(*&^$#@/MNBVCXZASqFGHJKLPOIUYTREWQ0987654321mnbvcxzasdfghjklpoiuytr"
+        right = "tyuioplkjhgfdsazxcv<nm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$^&*()_-+={[]}|:;?/>"
         self.assertEqual(sig(wrong), right)
 
     def test_86(self):

youtube_dl/extractor/youtube.py

@@ -186,7 +186,7 @@ class YoutubeIE(InfoExtractor):
         elif len(s) == 88:
             return s[48] + s[81:67:-1] + s[82] + s[66:62:-1] + s[85] + s[61:48:-1] + s[67] + s[47:12:-1] + s[3] + s[11:3:-1] + s[2] + s[12]
         elif len(s) == 87:
-            return s[62] + s[82:62:-1] + s[83] + s[61:52:-1] + s[0] + s[51:2:-1]
+            return s[4:23] + s[86] + s[24:85]
         elif len(s) == 86:
             return s[2:63] + s[82] + s[64:82] + s[63]
         elif len(s) == 85: