Sub-400ms end-to-end. That's the number that makes StreamTranslate captions feel synchronized with your speech. Here's exactly how we achieve it.
Try StreamTranslate FreeCaption latency accumulates across five stages: audio capture (near zero via Web Audio API), real-time connection transmission to advanced AI (10-50ms), enterprise speech AI ASR transcription (100-200ms), optional NMT translation (50-100ms), and DOM rendering (near zero). Total: consistently under 400ms on standard broadband.
our industry-leading speech AI uses streaming ASR that processes audio in small chunks as you speak, not waiting for complete sentences. This keeps the ASR stage at 100-200ms even for long utterances — the biggest contributor to the 400ms budget.
400ms is the threshold at which caption delays become perceptible as a disconnect between speech and text. Above 500-600ms, viewers watching video while reading captions experience a noticeable lag. Below 400ms, the delay is imperceptible in normal viewing.
Captions are baked into your stream video at the moment they appear. Even with 20-30 seconds of platform HLS latency, viewers see captions synchronized with the video frame they're watching — because captions appeared in the stream within 400ms of the speech in that frame.
StreamTranslate's full pipeline from speech to caption overlay consistently runs under 400ms on standard broadband connections.
our industry-leading speech AI processes audio chunks as you speak, keeping ASR latency at 100-200ms regardless of utterance length.
NMT for 125+ languages adds only 50-100ms, keeping translated captions under 500ms total.
Under 400ms end-to-end from speech to visible overlay — fast enough for captions to appear synchronized with your speech.
Audio capture (near zero), real-time connection transmission (10-50ms), our industry-leading speech AI ASR (100-200ms), optional NMT translation (50-100ms), DOM rendering (near zero).
Most competing tools add 1-3 seconds due to larger audio buffers. StreamTranslate's streaming ASR keeps latency under 400ms.
Internet speed affects real-time connection transmission (10-50ms on good connections). Higher-latency connections can add 50-200ms to total caption latency.
NMT translation adds 50-100ms on top of ASR. Total translated caption latency stays under 500ms.