Signature issue with some videos (URL for downloading a Youtube video)

Question

I’m having a problem with YouTube’s "Subscribe" get_video_info. I use this query for YouTube video data.

http://www.youtube.com/get_video_info?&video_id={VIDEO_ID_HERE}&asv=3&el=detailpage&hl=en_US

Its work is great, but some video download URLs are signed, and some are not.

Not working with this video ID : 9bZkp7q19f0 (PSY - GANGNAM STYLE Song)

Working with : jMXV0_cE-jQ (Alien Pranks - Best of Just For Laughs Gags)

I use asv = 3 and asv = 2. But the same problem.

What to do to get the ULR workload for all videos (instead of direct stream).

but you can download the " https://www.youtube.com/watch?v=9bZkp7q19f0 " video from savefrom.net. How will it work?

http://en.savefrom.net/#url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D9bZkp7q19f0&utm_source=ff-sf&utm_medium=extensions&utm_campaign=bookmarklet