MP4 Video with Transparent Background

Fellow Forum Members,

I'm currently getting a black box when I import my MP4 video into my Acrobat 10 generated PDF file.  I don't want BLACK to show instead of the black I need the first frame (what Acrobat calls the Poster Frame) to be TRANSPARENT.  I tried the idea already of using a transparent PNG file as the Poster Frame file but this does not work.  I still get BLACK. 

My only other idea is to somehow add to my MP4 video file a second of Transparent frames. This way when I embed it into my PDF the black will no longer cover up my PDF background.  My question: 

What tool do I use to add transparent frames to my MP4 video? 

I don't work with video, but is it possible that by using After Effects, I could add a transparent channel only for the first second of my MP4 video?  Will Acrobat 10 support a transparent video channel? 

I have been on this problem all day. Any help will be welcomed.  Thank you.