What is Lip Sync?
The match between a creator's mouth shapes and the audio they appear to be speaking. In AI UGC, phoneme-accurate lip sync is the single biggest tell separating ad-grade output from amateur output. Off-sync lips do not register consciously as 'AI' but register as 'something is off' and drop thumb-stop rate 20-30%.
Veo 3.1 (Google) currently leads on lip sync for English UGC content, with phoneme accuracy within 1-2 frames in 4 of 5 generations. Sora 2 (OpenAI) is visually plausible but specific consonant-heavy words (cramp, electrolyte) often have wrong mouth shapes that any English speaker catches within 2 seconds. For ecom UGC where ~80% of ads need a talking head, lip sync precision is the difference between a 30%+ 3-second view rate and an 18% one. Viewers do not need to articulate why an ad feels 'fake' — the unconscious mismatch is enough to scroll past.
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