bluray subtitle help

[oberon]

I have this movie I am trying to back up. Some parts of the video are subtitled when they speak another language. All the english subtitle tracks subtitle all the time. When I play the video normaly with subtitles off it still plays them when needed. How to I do the same for my backup?

[0xdeadbeef]

Though it's unclear what kind of backup you're up to: most BDs I got my hands on didn't have separate subtitle streams for "forced" subtitles. Instead, some captions were marked as "forced" in the normal stream.
BDSup2Sub (and AFAIK SupRip) has the option to only export these forced subtitles. Then again, it depends on your target format if it's possible to automatically play a subtitle stream.

[Adub]

Another option is to "burn" or hardcode the subtitles into your output using a filter such as VSFilter in Avisynth. But you will have to convert the Bluray subtitle so a more usable format first.