Alpha transparency with browser window on top

[coldfire]

the x11 video output module renders video under Unix env. i have installed the vlc firefox plugin and now i want to make the root window of plugin (i.e. browser) as alpha transparent. which i can do it separately by using xcompmgr (here) and transset-df (here). now i am integrating this in x11 code, is this the right way or i can do it another way? i also need to know that whether vlc-video output in fullscreen supports another window as overlay above it.

thanks