What do you mean with "not avaliable"?
Browser lack support of video formats?
http://camendesign.com/code/video_for_everybody
If you take a look at this guide, it will give you some great info about how to have different kind of fallback for different browsers when it comes to videos.
There they explain how to have a standard htlm5 video with flash fallback. If the client doesn't support flash, an image is displayed, that could be the banner you were talking about.
Video not avaliable in the dam?
If the video you are trying to show is located in the DAM, but somehow not working/is found, you have to have some kind code that checks for this. The code could fetch a video asset, check if everything is ok with it. If everything is allright, go ahead and display the video. If not, try to fetch the fallback image asset of your choice instead and display that one.
@smacdonald2008 has some good links there how to stard with the 3rd party plugins, and then try to customize it with something similar to the two hits above.
Good luck
/Johan
