Kling Lip Sync and Motion Brush: How They Work

Motion Brush and Lip Sync are two of Kling’s most useful controls for finishing a clip rather than generating it from scratch. Motion Brush lets you paint a region of your start image and draw the path it should travel, so you decide what moves and where. Lip Sync adds speech to a clip you have already generated, matching the mouth to audio. Each solves a problem that text prompts handle badly.

Motion Brush: paint what moves

Text prompts are vague about space. "The car drives to the right" does not say how far, how fast or along which line, and the model may move the background instead. Motion Brush replaces that guesswork with a mask and an arrow. You paint over the car, draw a path from where it is to where it should end up, and Kling animates that region along that path while leaving the rest of the image calm.

It works inside image-to-video, so you need a start frame. The tool suits:

• One or two objects that must move precisely. A hand reaching for a cup, a boat crossing a frame, a product sliding into position.
• Scenes where the prompt keeps animating the wrong thing. If the clouds move instead of the person, paint the person.
• Subtle life in a still. A short path on hair, a flag or steam gives gentle motion without disturbing the composition.

How to use it:

1. Upload the start frame in image-to-video and open Motion Brush from the controls.
2. Paint the region that should move. Cover the whole object, including edges, but do not spill far into the background.
3. Draw the path. Drag from the object’s current position to where it should finish. A short path means slow motion; a long path means fast motion over the same duration.
4. Mark static areas if the current interface offers a static or fixed brush. Painting the background as static reduces drift.
5. Write a light prompt. Describe the motion in a few words that agree with the path, for example "the red boat drifts slowly to the right, calm water". A prompt that contradicts the arrow produces a mess.
6. Generate at 5 seconds and check the painted region frame by frame.

Paint whole objects, keep paths simple, and remember that the model has to invent what is revealed behind a moving object, so motion across sky or a wall holds up better than motion across a busy background.

Lip Sync: add speech to a clip

Lip Sync takes a generated video that contains a visible face and re-animates the mouth to match speech. In the current interface you provide the speech either by uploading your own audio or by typing text and choosing a built-in voice; the exact options and supported languages vary by version, so check what is on offer before planning a multilingual project.

For good results the source clip matters more than the audio:

• The face should be clearly visible and roughly facing the camera. Profiles and heavy angles give weak sync.
• Keep the face large. A medium shot or close-up works; a full-body wide shot does not.
• Limit head movement in the source clip. Generate the clip with "subtle head movement, looking at the camera, static camera" so the mouth has a stable target.
• Match the length. Speech that runs longer than the clip gets cut; shorter speech leaves silent frames at the end.

A dependable approach is to generate the talking-head clip first with a neutral, slightly open mouth and calm expression, then add Lip Sync as a second step. If the clip is a recurring presenter, build them with Elements first; see Kling Elements for consistent characters.

Settings at a glance

Check the platform’s current pricing page for how each tool is counted in credits.

Combining them in one workflow

1. Create or generate a still of your presenter: medium shot, facing camera, plain background. The image-to-video guide covers preparing a good start frame.
2. Use Motion Brush to add a small, deliberate movement, such as a hand gesture or a slow lean towards the camera. Mark the background as static.
3. Generate at 5 seconds in Standard. Check that the face stays stable and the gesture reads clearly.
4. Open Lip Sync on the finished clip, add your audio or text, and generate.
5. Review with the sound on and off. With sound off you will notice any jaw jitter or mouth shapes that do not belong.

Common problems

• The painted object stretches rather than moves. The region was painted too loosely or the path is too long. Tighten the mask and shorten the path.
• The background moves too. Add a static region, or say "static background, camera does not move" in the prompt.
• Lips move but the face flickers. The source clip has too much head motion. Regenerate it calmer, then sync again.
• Speech is out of time. Trim the audio so it starts immediately and ends before the clip does, then re-run.

Try it

Start frame: a man in a grey jumper seated at a desk, facing camera, plain wall behind, soft key light.
Motion Brush: paint his right hand and forearm; draw a short path upward and slightly towards camera (a small welcoming gesture). Mark the wall as static.
Prompt: He lifts his hand in a small gesture and nods slightly, looking at the camera. Static camera, natural light, subtle movement.
Mode: Standard. Duration: 5 s.
Then: Lip Sync on the result with a 4-second line of speech.

If the hand works but the face wobbles, remove the nod from the prompt and let Lip Sync supply all the facial movement; one source of motion per region is the most reliable setup.