Sorry for not making this clear.
1) I am talking about a flash video in general, not specifically about a banner
2) I am using swfObject ver2.1 and in 2.1 you specify length and width.
3) If your video is in a 9:16 ratio but your space you are trying to put your video in is a 10:16 ratio you will get black space.
4) If you are putting your video on your main page (define_main_page.php) and you are using swfObject ver2.1 you can specify the size of the video:
Code:
var att = { data:"includes/templates/Series_12_Horses/flash/homepage.swf", width:"600", height:"240"};
(The above was copied from my site main page)
5) Note that the swf and the stipulated width and height (width:"600", height:"240") must be in the same ratio (mine is 1:1)
6) If it is not in the same ratio I BELIEVE the video will have black space.

This is all the info I have. I am not a programmer. Someone more skilled will need to help you further.

Best of luck.