Visemes
In VRChat, “visemes” are the 15 mouth‑shape targets that the Oculus LipSync library drives while you speak.
VRChat pipes your live microphone audio through that library, converts the sound into a single integer (0‑14) every video frame, and writes it into the built‑in Animator parameter Viseme (often shown in the docs as “VisemeOculus”). Your avatar’s FX layer (or the SDK’s default layer) turns that number into blend‑shape or bone animation so the mouth appears to pronounce your words in real time. See VRChat Creators Wiki
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Viseme Slots
| Index | Short code | Typical phonemes | What the mouth does |
|---|---|---|---|
| 0 | sil | silence / pause | Neutral, lips relaxed |
| 1 | pp | p, b, m | Lips fully closed, slight pout |
| 2 | ff | f, v | Lower lip touches upper teeth |
| 3 | th | th | Tongue between teeth |
| 4 | dd | t, d | Tip of tongue touches ridge |
| 5 | kk | k, g | Back of tongue touches palate |
| 6 | ch | ch, j | Lips rounded, jaw slightly down |
| 7 | ss | s, z, sh | Teeth almost together, lips wide |
| 8 | nn | n | Tongue presses ridge, lips apart |
| 9 | rr | r | Lips slightly rounded, cheeks firm |
| 10 | aa | a as in “father” | Jaw open, oval mouth |
| 11 | e | eh as in “men” | Mouth wider, mid‑open |
| 12 | i / ih | ee as in “meet” | Lips stretched, jaw higher |
| 13 | o / oh | aw as in “bought” | Lips rounded, jaw mid‑open |
| 14 | u / ou | oo as in “boot” | Lips rounded, slightly forward |
Oculus docs use the longer spellings ih/oh/ou; VRChat’s parameter list trims them to i/o/u.
Wiring Avatar
- Add blend‑shapes (shape keys) or a jaw bone. Each shapekey should be named exactly like the codes above (case‑sensitive in Unity). Keep the sil key—even if it only moves one vertex—to stop Unity deleting it on import.
- Set the Avatar Descriptor’s › Lip‑Sync mode to “Viseme Blend Shape”. Hit Auto Detect! first; if the SDK guesses wrong, pick the correct shapekey for every slot in the dropdown.
- Test in‑editor: play the scene, enable the Lip Sync preview on the descriptor, or simply talk into your mic while the Game view is active.
- Fine‑tune in your FX Animator (optional). The int parameter
Visemeupdates every frame; you can:- Drive a 15‑way BlendTree that weights each shapekey.
- Branch to custom mouth animations (e.g., a “big scream” version of
aa) when volume is high by also reading theVoicefloat (0‑1).
- Performance tip: keep viseme blend‑shapes on a separate head mesh; the GPU only has to update the vertices it actually changes.
Troubleshooting quick‑hits
| Symptom | Likely cause | Fix |
|---|---|---|
| Mouth never moves | Lip‑Sync mode still on Jaw Flap or Default | Switch to Viseme Blend Shape |
| Wrong shapes (e.g., “th” looks like “ff”) | Mis‑matched dropdown slots | Re‑assign each viseme in the Descriptor |
| Shapes snap instead of blend | Using an Int blend‑tree with thresholds too close | Use a 1D float tree driven by 0‑14 or add smoothing |
| Shapes missing on Quest | Head mesh not included in the Android build | In Build tab, mark head mesh for both PC & Android |
Take‑away
Visemes are simply numbered mouth cues. Name 15 blend‑shapes (or equivalent bone poses) to match the Oculus set, point your Avatar Descriptor at them, and VRChat’s built‑in Viseme parameter will make your character lip‑sync automatically—no extra scripts required.
