Guide
If the cameras had no timecode and nobody clapped a slate, the sync is done by audio. Resolve has a tool for it, and on short clean clips it works. On a long night, with the desk audio on one side and the camera microphones on the other, it stops. Here is where, and what to do.
Riccardo Tirincanti, SemSync, 2026-09-14
In the Media Pool you select the clips, right click, Auto Sync Audio, and pick Based on Waveform. Resolve compares the waveforms and moves the clips. It works well when the camera audio looks like the reference: same room, same moment, a few tens of minutes.
Where it stops: hour-long clips, cameras far from the speakers with the room's reverb, clean desk audio against dirty camera microphones, and the camera clock drifting all night long. In those cases the sync finds the wrong spot or nothing at all, and does not tell you.
Every camera has its own clock. Over six hours of a night two cameras can drift half a second apart, that is twelve frames. A sync done at the start of the clip is perfect at the start and out of sync at the end. No waveform sync fixes this: it moves, it does not stretch.
The manual cure is to cut the clip into pieces and re-sync each piece. On a night that is hours of work, and you get it wrong.
SemSync takes the folder with the cameras and the desk audio, lines every clip up on the audio of the night and measures each camera's drift along the whole night, not just at the start. Then it builds the timeline inside DaVinci Resolve Studio, with the native clips in place and the drift corrected. With free Resolve it writes the timeline file and you import it.
The numbers, measured: median error of 0.01 milliseconds over 33 known-truth cases, a six-hour night kept glued together, cuts on the frame 100% of the time over 1,110 cuts. When a clip does not lock, it says so and leaves it for you to place by hand: never sure about the wrong spot.
Questions
To have the project built inside Resolve, yes. With free Resolve SemSync writes the timeline file and you import it with File, Import, Timeline.
You use one camera as the reference. At the Cocorico' twenty clips out of twenty locked to each other without the desk.
Timed by the program itself: twelve minutes of machine time for two hours forty-five of footage across eighteen sources.
Club nights, festivals
Fourteen days, on everything, no card.