In television subtitling there are two types of subtitling:
- Open (burnt-in) subtitles
- Closed captions (teletext) subtitles
Titlevision can handle both, but not all file formats can save both types in the same file. (See below)
Open subtitles are always visible. They are a part of the television picture and cannot be switched off. The subtitle graphics are created by a subtitle keyer at the broadcasting station. This type is most common for translation subtitling.
Closed captions or teletext subtitles can be switched on or off by the viewer as they are transmitted as a separate stream. The actual subtitle graphics are created in the receiving television set. Teletext subtitles have certain limitations – the character set is limited and differs between countries, also only 37 characters per row are allowed. Furthermore, teletext subtitling uses monospaced fonts. Teletext subtitling is most common for subtitling for the deaf and hard of hearing, but is also commonly used for pay tv film channels with a need to broadcast multiple languages at the same time.
Mixed subtitling is when both open and teletext subtitles are saved in the same file. Only some file formats can save this variant: USF, 890 and XIF.
Preparing a mixed subtitle file in Sub Machine is easy as you may simply switch between open and teletext mode with a keystroke, a mouse-click, by selecting a range in the context window or by selecting Change text type on either the Edit or Format tab.
Saving a subtitle file with teletext markers into a format that does not save text type will make all the subtitles open when you re-open the file.
The pac format does not allow mixed files. Closed subtitles are treated as a separate language, thus needing a separate file.