Line 21

About Line 21

Line 21 provides live captioning for events and broadcasts, and its distinguishing position is that it treats human captioners and AI as complementary rather than as alternatives. The service can be run fully automated on ASR, fully human with professional captioners, or as a hybrid where speech recognition produces the base track and an AI proofreader corrects typos and name errors in real time against a context built for that specific event. That context builder is the part that matters for conferences and corporate events, where the words that break automatic captioning are almost always proper nouns — speaker names, product names, internal jargon — and can be loaded in advance as a custom dictionary. AI translation extends captions into 120+ languages using the same pipeline. Delivery is flexible: RTMP and HLS streaming, CEA 608/708 caption encoding for broadcast, an embeddable player that lets viewers pick their caption language, a standalone caption view page, on-screen overlays, playlists and an API. Platform integrations cover YouTube, Twitch, Facebook, Vimeo, custom RTMP destinations, Microsoft Teams, Skype, Zoom and AWS, and a meeting bot joins calls directly. The customer base is described as both organisations captioning their own next event and agencies white-labelling the technology for their own clients. Documentation and a blog accompany the product.

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