For Mac users please see the tips below on how to convert your video to mp4 before submitting:
Use QuickTime Player » Export » and select the format you want (iPad, iPhone, iPod, iTunes). Change the file extension from ".m4v" to ".mp4" and your video should be ready for upload.
For Windows users, we recommend using the VLC media player (free software). After you install it on your computer, follow the instructions in the link below to convert your video to mp4: