Offline, on-device live-caption translation for Android (captions in a different language than the speaker)
Users of an offline on-device speech-to-text / live-subtitle Android app are independently asking for captions to be translated into another language in real time — e.g. watching Chinese video and wanting English subtitles — not just transcribed in the same language. Every mainstream option misses this exact combination: Android Live Caption and Google Live Transcribe caption on-device but don't translate, while Google Translate's transcribe mode translates but is cloud-dependent. A FOSS, offline, real-time speech-to-translated-caption tool serves both deaf/HoH users and people consuming foreign-language media privately.
The hard part isn't translation quality — it's the end-to-end latency budget (on-device ASR chunk -> on-device MT -> overlay render) while staying offline. Reaching for a cloud MT API is trivial but destroys the privacy/offline value prop that makes users pick this over Google. Pairing a small on-device MT model (e.g. an NLLB distill) with the app's existing ASR is the real differentiator.
landscape (3 existing solutions)
Clear segmentation gap: on-device captioning tools don't translate, and real-time speech-translation tools are cloud-based, while OCR overlays only translate on-screen text. No confirmed FOSS, offline, real-time speech-to-translated-caption tool exists for Android.