SMI is HTML-like and many players outside Windows and Korea do not read it. EBU STL is the file European broadcasters ask for when subtitles are delivered with a programme. SMI is at home in subtitles for Korean-market players and multilingual files; EBU-STL is the usual choice for subtitles delivered to European broadcasters.
The text is read as UTF-8 or UTF-16, whichever the file is. An older file in another code page is read using the charset it declares, or as Windows-1252 if it declares none, so accented letters in an unlabelled legacy file can come out wrong. A file that is not text, such as the picture-based subtitles of a DVD, is refused instead of being converted to nonsense. Of the styling, only italic, bold, underline and the position on screen (top, middle or bottom, left, centre or right) travel between formats; fonts, colours, outlines and effects do not. A SAMI file can hold several languages; only the first one found is read. The file is written as STL25.01 in the Latin character set, 25 frames per second, with italics, underline, line breaks, position and justification. Characters outside the character set become a question mark.