You add dialogue to an AI animation by typing the lines: a voice model performs each one in the character's voice, the audio is time-aligned word by word, and the character's mouth animates to match. On stylised 2D characters the mouth work is done with lip flaps, swapped mouth states in the classic cartoon tradition, which is faster and considerably more reliable than regenerating video to match sound.
Two characters, typed lines, performed takes, animated mouths. This is the whole loop on screen, sound on:
Casting. Each character gets a voice picked once from auditions and kept, exactly like character art. A recast mid-film is as jarring in the ear as face drift is on the eye.
Performance. Modern voice synthesis reads intent from the writing, so punctuation and phrasing are directing tools. An exclamation mark is a note to the actor. So is an ellipsis.
Alignment. A forced aligner maps every word to its milliseconds, so the mouth and any gesture keyed to a word land exactly with the audio, not roughly.
The mouth itself. Stylised characters do not need photoreal lips; they need convincing rhythm. Swapping among a small set of mouth states, timed by the alignment, is how television animation has sold speech for seventy years. It reads instantly, and it never warps the face around the mouth.
Because it couples the cheapest change in film-making, rewriting a line, to the most expensive one, regenerating a shot. With flaps on top of finished video, a changed line is new audio, new alignment, new mouth timing, and the underlying animation is untouched. That decoupling is what makes dialogue iterable: you will rewrite lines ten times once you hear them performed, and each rewrite should cost seconds.
It also fails gracefully. A slightly-off flap is Saturday-morning charming. A slightly-off neural mouth warp is a horror short.
Read every line aloud before committing it; text that scans on the page can die in the mouth. Keep exchanges short, animation dialogue breathes in one-liners, not paragraphs. And give characters silence: a beat where a character just looks is a performance too, and generated films that never shut up feel generated.
For animation, yes, comfortably. Stylised characters set expectations that synthesized performance meets, and consistency of voice matters far more than any single line reading.
A tool that makes a character's mouth move in time with an audio track. For filmed faces it resynthesises the mouth region of the video. For 2D animation it picks from a small set of drawn mouth shapes and swaps them in time with the voice, which is how cartoon dialogue has always been done and why it holds up better on a stylised character.
The classic animation technique of switching a character's mouth among a few drawn states, open, closed, wide, in rhythm with the dialogue. Practically every TV cartoon you grew up with sold speech this way.
In a flap-based pipeline, yes: new audio is performed and aligned and the mouth retimes, with no re-render of the shot. That is the main argument for flaps over baked-in lip sync.
If the pipeline supports it, the same lines can be performed in another language with mouths retimed to the new audio. See the guide on making an animation in multiple languages.
Nima performs your script in cast voices and animates the mouths, and a rewritten line never costs a re-render. Try it free.
