If you are referring to those:
By opening any shitty stream from that website, the ad loads up with a flash object. I used "Live HTTP headers" for firefox to see where the SWF loads from, then used wget to download that SWF object. After obtaining it, I used a website
http://www.showmycode.com/ to extract the code and did some visual inspection and on line 2453 I noticed this:
this.adUrl_vl = ((((("http://vast.yashi.com/3183&vid_id=" + this.streamNet) + "_") + this.streamChan) + "&vid_title=") + this.streamChan);
Now, without going too deep, I added this:
||vast.yashi.com/*
to uBlock for Firefox (because fuck adblock, refer to this thread:
https://evilzone.org/general-discussion/should-people-use-adblock/) and after refreshing the website, those ads didn't come up. So there.
However none of the streams I tried played for me, meh. At least no ads!