The very best one I found is not free but is reasonably priced. They used to give a 45 day free trial (no watermarks) followed by an unconditional 30 day money back guarantee. I bought it because it gave me the best quality of about 15 that I tried. I was changing students' PPTs to swf with i-Spring Pro and then from swf to flv or avi to use in Adobe Premeire Elements. Adobe says PE takes swf files, but I have never been able to get them to work.
It's from Bytescout --> http://bytescout.com/swftovideoscout.html. Good luck!
as I know moyea swf to video converter is famous for swf conversion,
with which you can convert both online swf url and offline swf files to any video, audio and picture formats you want, http://www.swfkits.com/swf_to_video/