Convert smi to sub

What is the difference between .smi and .sub?

Description: SMI (Synchronized Accessible Media Interchange) is a file type associated with multimedia presentation files. It is used to store captions and subtitles for multimedia files as well as other data such as timing information, font information, and language information. It is commonly used for videos, DVDs, and other multimedia content.; MicroDVD is a subtitle file format for digital video. Its name is derived from the MicroDVD Player, a media player application designed to play DVD videos along with subtitles, originally developed by Tiamat Software. The application was first released in 2000 but development ended in 2001. Media players that support the format are able to interpret MicroDVD subtitles and mix their contents with their corresponding video files.