There used to be a free Mac utility program called StereoSplicer which can extract the left and right AVI files from the Fujifilm W3 along with splitting the left and right images from the .MPO. (You can use Stereo Photo Maker for the .MPOs but not the 3D AVI files. You need their StereoMovieMaker app but it runs mostly on Windows).
The StereoSplicer app is no longer available but you can grab it from:
https://macdownload.informer.com/stereosplicer/
(Yes, the website looks sketchy, but the file is there.)
Unfortunately, it won't work on new Mac OS versions but I have access to an old MacBook Air running Mac OS X Leopard and the program works fine.
