<object classid="clsid:xxxxxxx-yyyy-22ll-74455-45455545222" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0" width="1000" height="550">
<param name="movie" value="nome_file.swf" />
<param name="quality" value="high" />
<PARAM NAME=wmode VALUE=transparent>
<embed src="nome_file.swf" quality="high" wmode=transparent pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="1000" height="550"></embed>
</object>

aggiungi le parti segnate in rosso sull'html.
cosi il tuo filmato avrà come sfondo quello della pagina