document custom theming for video module

I need to change the output that the function theme_video_play_swf provides (in video/includes/common.inc) . While I can edit the function itself to customize it to my needs, I would be modifying the video module code.

I added a "phptemplate_video_play_swf" function to my custom theme, as , but my custom theme function did not get called.
Can you tell me if it's possible to customize the output of this function without resorting to modifying the video module?

Thank very much.