Forced Subtitles
Forced subtitles appear in many movies and only provide subtitles when the characters speak a foreign or fictitious language, or a sign, flag, or other text in a scene is not translated in the localization and dubbing process. These subtitles, although in less than half of the commercial motion pictures available, are still commonplace.
There is a distinction between "narrative subtitles" and "forced subtitles" in that subtitles in DVD and Blu-ray motion picture media are optional and provide text for all dialog in a movie, while "forced subtitles" are shown regardless of current player setting, typically when movie contains a foreign language scene.
In VHS and early DVD movies the forced subtitles were graphic images that were part of the video itself. Later DVD and all modern Blu-ray use an overlay on top of the video itself. The text for the overlay comes from formatted text in a track or file. On Blu-ray, each subtitle item has an attribute that specifies whether particular subtitle appearance should be forced.
For example, if you are an English speaking person watching a French film in which all dialog is French, and you are not bilingual, you will wish to have complete narrative subtitles for all dialog in the film.
If you are an English speaking person watching an English movie with mostly English speaking characters and a few scenes of characters speaking in a foreign language, you might find it annoying to have complete narrative subtitles throughout the film. You only require subtitles when the foreign language dialog is spoken. In this case, you desire "forced subtitles," which are those that only appear in the few foreign language parts.
Your DVD or Blu-ray player is going to display the forced subtitles by default. You won't have to change any settings for them to automatically appear during the non-English parts. However, if you download a movie (one that is public domain) from the Internet, you may have to obtain a separate subtitles file for those parts, depending on the format of the video. Furthermore, you may be out of luck, considering some of the poor quality stuff being put out today by encoders. The forced subtitles may be absent and unavailable altogether. You won't have this problem if you buy the DVD or Blu-ray.
In the process of digitally archiving DVD and Blu-ray media into re-encoded video files for storage on a computer or PVR media device, people sometimes neglect, often by accident or due to being ill informed, including the forced subtitles in the movie. They are not automatically captured by many "ripping and encoding" software. The result could be a minor problem of a few scenes without the necessary subtitles or a major problem where enough non-English dialog is not available as translated text, resulting in degrading the viewer's understanding of the plot and storyline of the movie.
Including forced subtitles in archived movies is not only a quality control issue, but is in consideration of capturing the movie in its completeness for future enjoyment. It requires a few extra steps, but it is always possible to capture those forced subtitles. The forced subtitles can be "burned in" the video itself, included as a separate file, or contained within a file format such as Matroska.
If you archive your own Blu-ray and DVD media as a backup or convenience of having all the video files on a media center, be sure to include the forced subtitles for movies that have them. The best process as of 2014 is to encode in [H.264]] and include a forced subtitles file (.srt) with the forced flag set, and the narrative subtitles file all within the Matroska (.mkv) file container. This results in a single file that will contain the movie, forced subtitles, and optional narrative subtitles. You will benefit from an archive with high quality video and no absent dialog translations.
