Tutorials
Which AI Video Model Is Best for Lip Sync and Dialogue?
For scenes with spoken lines, use a model that generates audio with the picture: Seedance 2.5 for references and long takes, Veo 3.1 or Kling 3.0 for short spoken shots. Then check every line, because no model gets all of them right.
For dialogue, the best AI video models are the ones that generate speech together with the picture, because the mouth and the voice come out of the same generation. In MoviePro that's Seedance 2.5, Veo 3.1, Veo 3.1 Fast, Kling 3.0, LTX-2.3 Pro and Cinema Studio 4.0; of those, Seedance 2.5 is the most flexible for dialogue scenes, and Veo 3.1 and Kling 3.0 suit short spoken shots.
The more useful answer is that no model says every line correctly every time. Native-audio models sometimes slur a word, swap one for something that sounds similar, or clip the end of a line. So the best dialogue workflow is a good model plus a check of every take, plus a way to fix the lines that slip.
Which models generate speech with the video?
These are the video models in MoviePro that can generate audio with the picture, as of October 2026:
| Model | Clip length | Reference images | Reference audio | Credits per second (with audio) |
|---|---|---|---|---|
| Seedance 2.5 | 4–30 s | Up to 30 | Up to 10 clips | 4 (480p), 9 (720p) |
| Veo 3.1 | 4, 6 or 8 s | None | None | 14 |
| Veo 3.1 Fast | 4, 6 or 8 s | None | None | 6 |
| Kling 3.0 | 3–15 s | None | None | 9 (720p) to 15 (4K) |
| LTX-2.3 Pro | 6, 8 or 10 s | None | None | 3 (1080p) to 12 (4K) |
| Cinema Studio 4.0 | 4–30 s | Up to 30 | Up to 10 clips | 8 (480p), 17 (720p) |
The other models (Wan 3.0, Runway Gen-4.5, Hailuo 2.3, the Seedance 1 models and MiniMax Director) make silent video. You can still give their shots dialogue with a lip-sync pass afterwards, covered below.
Which one should you choose for a dialogue scene?
It depends on the shot more than the model's reputation.
- A conversation between recurring characters: Seedance 2.5. It's the one that combines native audio with large reference sets, so the same faces can speak across a whole scene, and it takes up to 30 seconds when a beat needs to play out.
- A single short line, photoreal, one character: Veo 3.1, or Veo 3.1 Fast at under half the price. Their 8-second limit fits one or two sentences.
- Short spoken shots where you need 1080p or 4K: Kling 3.0, up to 15 seconds.
- Lower-cost spoken shots at 1080p: LTX-2.3 Pro at 3 credits per second.
- Directed shots where camera, lens and grade matter as much as the line: Cinema Studio 4.0, which takes those as settings and also generates audio.
Whichever you choose, generate one take of one dialogue shot first and listen to it closely before you run the scene.
Why do AI characters slur or change their lines?
Because these models generate speech, they don't play back a recording. The words are produced along with the mouth movement, and the model can drift towards something that sounds plausible rather than what you wrote. In our own work we've seen Seedance 2.5 render "Wall Street" as something closer to "Walfreet" and cut the last word of a line that ran too close to the end of the clip. Other native-audio models do the same kind of thing at different rates. It's a property of generated speech, not a bug in one model.
Three things make it more likely:
- Long lines. The more words in one shot, the more chances to slip.
- Unusual words. Names, jargon and numbers are the most often mangled.
- Lines that fill the whole clip. Leave a second of air at the end.
Pronunciation notes in the prompt helped less than we expected. Shorter lines helped more.
How do you check that every line is right?
Transcribe each take and compare it with the script. Listening works for a few shots, but over a whole film your ear starts filling in the words you expect to hear.
MoviePro's Generate Shots does this automatically and for free: every take with dialogue is transcribed and compared with the shot's line, and mismatches show on the row as "Dialogue check: heard … for …" (Dialogue that lands).
One detail matters if you build your own check: use a transcription model that writes down what was actually said. Some newer speech-to-text models quietly correct speech towards plausible text, which hides exactly the slurs you're trying to catch. MoviePro's check uses OpenAI's whisper-1 for that reason.
How do you fix a line that came out wrong?
Pick the fix by what's wrong. Here are the options in MoviePro and what each costs:
| Problem | Fix | Cost |
|---|---|---|
| Slurred or garbled line, picture fine either way | Generate another take | The shot's normal price |
| Wrong words, picture is good | Fix dialogue: transcribe, edit the line, re-voice it in the character's voice | About 3 credits a scene plus 1 per changed line |
| Mouth doesn't match the new words | Give this clip a line, then Lip sync | 2 credits per second |
| Right words, poor sound | Fix dialogue → Re-voice as is | About 3 credits a scene plus 1 per line |
A note on remaking a take: using a previous take as a reference video, with the correct line as reference audio, tends to reproduce the old take's audio, slip included. It keeps framing and motion, but it doesn't fix a misspoken line. Re-voice and lip-sync instead.
When should you lip-sync instead of generating speech?
Sometimes it's better to separate picture and voice from the start:
- The line is long or precise. A legal disclaimer, a product name, a poem. Record or synthesise it exactly, then lip-sync the clip to it.
- The voice must match across many shots. Give the character a designed or cloned voice (with permission), and use it for every line. In MoviePro a character's voice lives on its element in Cast & Elements (Build your cast).
- You're using a silent model. Generate the performance on any model, then lip-sync it.
- It's a presenter or a talking head. Avatar Studio's Avatar tab makes a portrait speak a script or an audio file, with OmniHuman 1.5 for up to 35 seconds or Kling Avatar for up to 60 (Avatars and character replace).
How should you write dialogue for AI video?
Write for the medium:
- One or two sentences per shot. If a speech runs longer, split it across shots and cut between speaker and listener, as any editor would.
- Name the speaker on every line. In MoviePro's shot list, dialogue goes in the shot's Dialogue field as NAME: line.
- Leave room at the end. Generate a clip a second or two longer than the line.
- Avoid hard-to-say words in key lines. If a name keeps coming out wrong, consider whether the scene works with "she" instead.
- Use cutaways. A reaction shot of the listener lets you lay a re-voiced line over a picture where nobody's mouth needs to match.
The course lesson Recording dialogue covers the same choices from the live-action side, and Mix the sound covers sitting dialogue, music and effects together.
So which model is best?
For most narrative dialogue in MoviePro, start with Seedance 2.5, because it can hold a cast's faces through references while generating speech. Reach for Veo 3.1 or Kling 3.0 for short, single-speaker lines, and LTX-2.3 Pro when budget matters. Then treat the dialogue check as part of the render, not an extra step. A model that gets eight lines in ten right, with the other two fixed by re-voicing, gives you a finished scene. For what each option costs over a whole film, see how much AI video costs per second.
