what are you putting into your qt video.
if you have linked a qt movie into your flash, and
then exported is as a qt, i think,
that the qt layer stays in exactly the same compression format it always was (cos flash is actually not doing anything to the qt, it is just adding a layer to the quicktime known as as flash track)
but the flash componemts, animations and stuf that you are
putting into your quicktime, are retained in there vector format on a different layer as a ,swf track, so the only compression is what you have specified in the output settings for flash.
i think tht is right