How to sync your voice to the picture: lip sync in dubbing
What separates a believable dub from someone just talking over a video is sync: the voice starts when the lips part, breathes when the character breathes and goes quiet when they go quiet. Here's how to get there.
What is sync in dubbing?
In the dubbing world, sync means how well the voice matches what's on screen. It comes in several layers. The most visible is lip sync: when the character's mouth opens you should hear a sound, and when it closes you should hear a consonant that closes the lips. Then there's rhythmic sync: your line should last as long as the character is talking. Finally there's emotional sync: if the character flinches, laughs or looks down, your voice should show it at the same moment.
Viewers can't always say what's wrong with a bad dub, but they feel it right away. A good sync, on the other hand, makes you forget the voice was added afterward.
1. Nail your cue
Your cue, or attack, is the very first sound of your line. It's the most important moment, because that's when the eye checks that the voice really "belongs" to the face. Coming in half a second late is enough to break the illusion, even if everything else is perfect.
To nail it, watch the character's mouth rather than your script just before they speak. Breathe in right before, and say the first word as the lips part. In TryToAct, a countdown comes before each take: use that time to get in position and spot the first mouth movement, rather than to reread the line.
2. Spot the lip consonants
The consonants B, P and M are said with closed lips. They're the only ones you can check by eye, which is why professional dubbing writers hunt for them: if the character closes their mouth on screen, the translated script ideally puts one of these consonants in the same spot. Wide-open sounds like "ah" or "oh" line up with the moments when the mouth opens wide.
You don't need to rewrite the script to play, but spotting these moments helps a lot: if you know the character closes their mouth at the end of the sentence, you know exactly when your line has to end.
3. Match the length of the line
Every line has a length set by the picture. If you talk faster than the character, you finish while their lips are still moving; if you talk slower, your voice spills into the next shot. The right habit is to count the length of the original line in your head, then adjust your pace.
• If your version is too long, don't just speed up: cut a filler word or a hesitation instead.
• If it's too short, stretch the vowels or add a breath, an "um" or a little laugh, as long as it fits the character.
• Spot the pauses inside lines: a character who stops mid-sentence should stop in your version too.
4. Bring the pauses and breaths to life
Beginners tend to fill every second. But a character who's listening, hesitating or taking in bad news isn't talking: they breathe, sigh, swallow. Those little sounds bring a dub to life. When the character takes a visible breath before shouting, take one too. When they stand there open-mouthed, stay quiet.
On the flip side, don't let your own breaths be heard in the middle of a sentence where the character doesn't take one. Breathe before the line, while their mouth is closed.
5. Follow the body, not just the mouth
Sync isn't only about the lips. A character who's running is out of breath. A character who spins around suddenly speaks with a little jolt. A character seen from behind or far away gives you more freedom on the lips, but not on the energy: if they're waving their arms around, your voice needs to be lively.
Many voice actors physically act out some of the gestures while recording: shrugging, pointing, stepping back. Your body drives your voice, and the result naturally fits the picture better.
A four-pass method
• First pass: watch the scene without recording, following only the character's mouth.
• Second pass: whisper your line along with the original to feel its length and its pauses.
• Third pass: record at full voice, focusing on the start and the end.
• Fourth pass: play your take back with the picture. Note the spot that drifts the most and do another take fixing only that.
In TryToAct, playing back your take shows a waveform you can scrub through to find a specific moment. It's the perfect tool to check where your voice starts compared with the picture.
What if you're going for laughs?
Parody dubbing plays precisely on the gap between what you see and what you hear. But even then, sync is your best friend: an absurd line that lands right on the lip movement is far funnier than an absurd line that's out of sync, because the viewer believes it for a split second. To go further, read our guide to making a funny dub that works.
To see how professional studios handle this work at scale, with the rythmo band (the scrolling strip of text French dubbing studios use) and script adaptation, read our article on how a French dub is made (in French).
Frequently asked questions
What does lip sync mean in dubbing?
It's the match between the lip movements on screen and the sounds you hear: mouth open on vowels, lips closed on the consonants B, P and M.
I always finish too early. How do I fix it?
Stretch the vowels rather than the consonants, keep the character's pauses, and add a breath or a hesitation if it fits the scene.
Do I need to know my lines by heart?
You don't have to, but knowing them well enough to watch the screen when your line starts makes your sync much better.