Syncing sound and picture: timecode, the clap and waveform in DaVinci Resolve
The three ways to line up dual-system sound, why waveform sync needs no hardware box, and what to do when auto-sync fails on a noisy or long take.
By Hanna Eng·Video editor, Free Conservatory of French Cinema
There are three ways to sync sound and picture in editing: matching timecode, lining up the clap, or aligning the audio waveforms. Waveform sync, built into DaVinci Resolve, handles most projects with no hardware timecode box and no plugin. When auto-sync fails, you fall back to the clap or set a manual offset on a sharp transient.
When sound is recorded separately from the camera, called dual-system sound, the first job in the edit is to put the two back together in sync, to the frame. There are three ways to do it, and the good news is that the most reliable one for everyday shoots needs no extra hardware at all. Here is how each method works, how to do it in DaVinci Resolve, and how to rescue a take when the automatic sync gives up.
Three ways to sync sound and picture
| Method | How it works | What it needs |
|---|---|---|
| Waveform | Matches the audio peaks of the camera scratch track against the recorder file | Scratch audio on the camera, no extra gear |
| Timecode | Matches a shared clock stamped onto every file | A camera and recorder that support timecode, or a generator |
| Clap | Aligns the sharp spike of the clap to the frame where it closes | A clap or slate at the head of the take |
The three ways to sync sound and picture
Every sync method answers the same question: where in time does this audio file line up with this video clip. Timecode answers it with a shared clock, the clap answers it with a visible and audible marker, and waveform sync answers it by matching the sound itself. Most projects use one as the primary method and another as the backup.
The table above sums up what each needs. The key point for a solo or small shoot: you do not need a hardware timecode box to get frame-level sync, because waveform matching does it from the camera's own scratch audio.
Waveform sync: the no-box default
Waveform sync works as long as the camera captured the same sound the recorder did, even as a rough scratch track. The software compares the shape of that scratch track against the clean recorder file and slides them until the peaks line up, which lands at frame level when there is a clear shared sound to match.
This is the everyday method for dual-system sound and it needs no hardware timecode box and no separate sync plugin. The one requirement is overlap: the camera and the recorder both have to have captured the same moment of sound.
Timecode sync: when the gear supports it
Timecode stamps every frame with a shared clock so the camera and recorder agree on the exact moment of each file. When both devices are jam-synced to the same timecode, the edit software can line clips up instantly with no audio matching at all, which is why timecode is the standard on multi-camera and larger productions.
The catch is that it needs gear that supports it on both ends, or an external generator. If only the camera or only the recorder has timecode, the shared clock is missing and you are back to waveform or the clap.
The clap: the original sync point
The clapperboard predates both methods and still works. Closing the clap makes a single sharp spike you can see on the picture (the sticks meeting) and hear as a tall transient on both audio tracks. Line the spike up with the frame where the sticks close and the take is synced.
It is the dependable fallback: even with no timecode and a scratch track too noisy for waveform matching, a clean clap gives you one unambiguous point to align to.
Syncing in DaVinci Resolve, step by step
In Resolve, select the matching video and audio clips in the Media Pool and use Auto Sync Audio, choosing by waveform when there is scratch audio or by timecode when both files carry it. Resolve aligns them and can append the clean recorder audio to the clip in place of the scratch track.
Always verify the result on a sharp transient, a clap, a door, a hard consonant, rather than trusting the lip movement alone. If the peaks sit exactly on top of each other, the sync is good.
When auto-sync fails: drift, no clap, dual-system
Auto-sync fails for a few predictable reasons: no overlapping sound to match, a scratch track too noisy to read, a sample-rate mismatch between devices, or clock drift on a long take where the camera and recorder run at slightly different speeds. Drift is the sneaky one: the head syncs perfectly and the tail slips.
The manual fix is to find one clear transient near the start, set the audio offset so it lines up, then check a second transient near the end. If the tail has drifted, the take needs splitting and re-syncing in sections, or a sample-rate correction. A wrong project frame rate, for example 23.976 treated as 24, is a common hidden cause.
Common sync mistakes
The recurring errors: assuming you need a hardware box you do not have, not recording any scratch audio on the camera (which kills waveform sync), ignoring drift on long takes, and working in the wrong project frame rate. Each one turns a two-minute job into an afternoon.
The reliable habit is simple: always capture a scratch track, always include a clap when you can, and always verify sync on a transient at both the head and the tail of the take.
Frequently asked questions
How do you sync sound and picture in DaVinci Resolve?
Select the matching video and audio clips and use Auto Sync Audio, by waveform when the camera has scratch audio or by timecode when both files carry it. Then check a sharp transient to confirm the peaks line up.
Can you sync audio and video without timecode?
Yes. Waveform sync matches the camera's scratch audio against the recorder file and gets you to frame level with no hardware box or plugin, then you confirm on a sharp transient. The clap is the fallback when the scratch track is too noisy to match.
Do you need a hardware timecode box to sync sound?
No. A timecode box or generator makes multi-camera sync fast, but for everyday dual-system shoots waveform sync does the job from the camera's own scratch audio, with no extra gear.
How does syncing with a clap work?
Closing the clap makes one sharp spike that is visible on the picture and audible on both audio tracks. You align that spike to the frame where the sticks close, which syncs the take.
Why does my audio drift out of sync over a long take?
The camera and recorder can run at slightly different speeds, so the head syncs but the tail slips. Fix it by re-syncing in sections or correcting the sample rate, and check the project frame rate is right.
What is the difference between waveform and timecode sync?
Waveform sync matches the recorded sound and needs no special gear; timecode sync matches a shared clock and is faster but only works when both devices stamp timecode.
How do you check that sync is correct?
Find a sharp transient such as a clap, a door or a hard consonant and confirm the peaks on the two tracks sit exactly on top of each other. Check both the head and the tail of the take for drift.