How can I convert my existing videos into the required MP4 format?I recommend using the ffmpeg command line tool that is available for most platforms.
Tip (especially when converting PAL and NTSC based videos): ensure that the resulting video has a Pixel Aspect Ratio of 1:1. Otherwise your videos might not be displayed in the correct aspect ratio
ffmpeg -i my_video.avi -y -c:a aac -c:v h264 -vf scale=iw*sar:ih my_video.mp4
This will convert “my_video.avi” into a compatible mp4 file and ensure square pixels.