Vast adserver questions: where to get the ad tag url?
I am a newbie to vast. From what I read in JWPLAYER docs, I should send a request from my player to a so-called 'adserver',parse the response, and display the ad. Now my quesiton is : where to get the the adserver url? I checked all the websites listed in jwplayer's docs,such as openx, 24*7,yume, but all i got is some fancy promotion stuff about how their service can help business. I thought adserver is like an api which,after i send a request, would give me a response. But apparently this is not the truth. can anyone give me any advice on how to get access to an adserver so that I can at least test the ad display on my player?
P.S. I looked into google adsense,too, but it require 2million impression per month. I have just started my website....
any help is greatly appreciated!!