NihonSub: Open-Source Real-Time Anime Subtitle Engine Built on Whisper + DeepSeek
Grand_Marionberry115 · reddit · 2026-10-05
A Reddit user open-sourced NihonSub (MIT license), a real-time translation engine and synced cinema player that turns raw Japanese videos into context-aware bilingual subtitles.
Traditional MT struggles badly with anime: it butchers honorifics, sentence-ending particles (-tteba, -zo) and character slang; pro-drop grammar causes inconsistent pronoun translation line by line; and cloud transcription APIs choke on background music and screaming.
Pipeline architecture:
- ffmpeg silence detection for VAD chunking, slicing utterances at natural speech pauses without cutting words
- Whisper-Large-v3 on Groq LPUs for near-instant Japanese transcription
- Transcript translated via DeepSeek / LLaMA-3 (Groq or OpenRouter) with a prompt enforcing anime nuance, honorific preservation, and character tone, outputting Hindi and English simultaneously
- Custom WebVTT generator and dual-subtitle player with timestamp scrubbing
The author argues LLMs far exceed naive NMT at resolving who is speaking to whom from context and tone. The entire pipeline runs on free-tier APIs (Groq + OpenRouter) with zero subscription cost. Feedback is welcome on local edge optimization such as Whisper.cpp or local Ollama.
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