using media tag mod

trying to build tag for ustream and seem to have issue with regex in media replacement

source for testing is nasa channel

http://www.ustream.tv/channel/6540154

with embed code

<iframe width="480" height="270" src="http://www.ustream.tv/embed/6540154?html5ui" scrolling="no" allowfullscreen webkitallowfullscreen frameborder="0" style="border:  none transparent;"></iframe>

so the media replacement match

 

should be this right?

http://www.ustream.tv/channel/(\d+)?

with replacement html

<iframe width="480" height="270" src="http://www.ustream.tv/embed/$1?html5ui" scrolling="no" allowfullscreen webkitallowfullscreen frameborder="0" style="border:  none transparent;"></iframe>

correct?

the (\d+)? because there are only digits and no trailing / or anything and the $1 where that number is referenced in html right?

system just creates blank iframe with no content and I cannot see why.

 

could really use some help here. pita to embed livestream / ustream stuff