First there are free video converter and paid video converter, second there are video converter for windows OS and video converter for Mac OS. For free video converter, I think Handbrake is the best and paid video converter, you can find many on the internet, such as Aiseesoft Total Video Converter, Aiseesoft Video Converter for gay porn Mac, Anymp4 Video Converter, Any mp4 Video Converter for Mac.
You can find some video converters has the 3D function, which will help you to convert 2D video to 3D, like Aiseesoft Total Video Converter Plaitnum and Aiseeosft Mac Video Converter Platinum.
Just a little about the video converter, hope it will help you guys.