When you need to split
Your player only wants a single-language track; or you want the translation track for a re-translation, or the original track to pair with another translated version. A bilingual subtitle is either one cue with two lines (original on one line, translation on the other) or two separate cues sharing the same timeline — both can be split.
Where to do it
Open the Bilingual Subtitle Stripper and drop in your subtitle. The tool detects the bilingual form automatically: one cue with two lines is split by writing system, two cues on the same timeline by order. Pick Split into two in the mode dropdown and click Start (or let it re-run automatically). The result area shows two pieces: the one tagged `.orig` is the original track, the one tagged `.dst` is the translation track — click “Download” for each; the two tracks share exactly the same timeline.
One common pitfall
One cue with two lines in languages that share the same alphabet (say English plus French) cannot be split. When tracks are separated by writing system, those count as one system and get treated as monolingual. Convert such content to the same-timeline form B first, then split; the two-cue form pairs by timeline and does not care about language. For the ins and outs of both forms, see Two ways to make bilingual subtitles.