We can not fetch videos from this type of page.
Your URL was: http://save-video.mp4?http%3A%2F%2Fv5.lscache7.c.youtube.com%2Fvideoplayback%3Fip%3D0.0.0.0%26sparams%3Did%252Cexpire%252Cip%252Cipbits%252Citag%252Calgorithm%252Cburst%252Cfactor%26fexp%3D906300%252C905208%26algorithm%3Dthrottle-factor%26itag%3D18%26ipbits%3D0%26burst%3D40%26sver%3D3%26expire%3D1258520400%26key%3Dyt1%26signature%3D9376CBC3650C70B283ACFB889B9BAF7C9AB39932.541770E31CD107CE22471B82157B280C40067B5F%26factor%3D1.25%26id%3De5739a3480d0ac71
The URL must be like http://www.youtube.com/watch?v=KPtX7hak0Qs
https://www.
and replace with pwn
Example: