A digital video consists of a computer file called the container
In this file we find:

Limitations :

Unlike music files, which are widely portable from one device to another, videos require a certain amount of juggling between various formats to adapt to the equipment used to play them.
A video rendered for a "Home Cinema" device can occupy several Gb and will be unreadable on a smartphone.
The same video rendered for a smartphone will require only one Mb, and can be played on a "Home Cinema" device but it will look ugly.
That is why we recommend that you preserve your original project files as far as possible, and create from them videos suitable for the devices you wish to use for playback.

To simplify settings for the rendering operation, ffDiaporama contains predefined settings for the following devices:
It is also possible for you to define all parameters directly by using the advanced option.