What I am using is this popular Video Converter Mac program: Moyea Video Converter Mac.
It supports converting among almost all video and audio formats including any kind of common videos on your PC, your videos from DVs or
camcorders (JVC, Panasonic, Cannon, Sony, etc.),
DVDs (*.vob, *.mts, *.m2ts, etc.),
YouTube (*.flv, *.f4v), etc. for all popular portable devices like
iPod, iPhone, PSP, Xbox, Zune, Creative Zen, cell phones and so on.
The best important factor attracts me to choose the program is that it is guaranteed with totally audio and video synchronization from its official website.
And the result after trying several kinds of videos is really satisfying.
So I think it can solve your problem successfully and you can have it a try.
For more information please refer to:
http://www.my-video-converter.com/videoconvertermac/