Apple embeds standard meta data in video and photo files produced by iDevices such as iPhones and iPads to determine orientation.
This is done so that no matter how you hold the device the video and photos are always right side up. Because physical cameras do have an up and down to them. If you rotate a camera then the video will be rotated as well.
If the software being used to view these files does not read or correctly identify the meta data for orientation it will not correctly rotate the video. And as such will not be correctly dispalyed.
This is more of a failure form the software playing back the video then the iPad or iPhone itself.
The easy way to remedy this, is to make sure the iPad or iPhone is held in the correct orientation when filming or taking pictures.