There's nothing more annoying than not being able to watch a film or video because it's not in the right format for your device or player, or not being able to edit it because of the format.
The only solution in such cases is to use a video converter, although results can differ in both speed and quality, depending on which software you use. Tipard Video Converter for Mac seems to perform well on both counts, conducting quick and reliable conversions. It can handle a huge number of formats including AVI, MP4, MPG, Mod, TOD, MOV, MKV, WMV, DivX, XviD, MPEG-1/2, 3GP, 3G2 and VOB. Its main output formats are MP4, AVI and Xvid which should cover most mobile needs including iPhone, iPod, Sansa, Sony Walkman, Creative Zen, Apple TV, Nokia, PSP and Zune.
Tipard Video Converter for Mac allows you to configure encoding parameters such as resolution, encoder, frame rate and video bitrate. It also allows a certain degree of editing through a trim and crop function, although this is rather limited. The main problem you'll experience however is instability. Tipard Video Converter for Mac crashed a few times before I eventually got to the conversion stage.
If you can deal with the odd crash though, Tipard Video Converter is a very well-presented and easy-to-use video converter that covers almost every possible conversion format need.