iDealshare VideoGo is definitely the best choice to rotate MP4 videos.

It can rotate MP4 without re encoding, which make the MP4 rotating progress much faster as well as keep the original video quality.

It also supports rotating MP4 as well as convert to another video format.

With this nice MP4 Rotator, it is just a piece of cake to rotate or flip all MP4 videos 90 degrees, 180 degrees, 270 degrees and more.

It also can rotate AVI, WMV, MOV, MKV, VOB, MPG and etc

Step by step guide at http://www.idealshare.net/how-to-rotate-mp4-video.html