Sync podcast cameras without a clap

By timecode, when it agrees

If a camera writes timecode into its file and it agrees with the sound, that’s used. If the cameras share timecode with each other but not with the Mac’s clock, their timecode places them against each other and the sound only places the group. Timecode is compared in real seconds, so it lines up even if the cameras started minutes apart.

By sound, when it doesn’t

Without timecode — or when it doesn’t agree — OnAirCut compares each camera’s own audio with the mics’ tracks, to a fraction of a millisecond. It needs at least five seconds of audio in common; a whole podcast has plenty.

The drift nobody sees

Two clocks never run at exactly the same speed. A difference of 30 parts per million is 0.1 s in an hour — enough for a cut to land on the wrong syllable by the end. OnAirCut measures each camera’s drift and corrects it on every cut, and checks the sync at many points along the recording.

If the points don’t agree — a video from another day, say — the camera says Unconfirmed sync and the export warns about it, instead of quietly delivering a bad edit.

Frame rates and drop frame

• 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60.
• Timecode is read the way the camera counts it — one at 59.94p usually counts at 30 — and exported the same way.
• Drop frame exists only at 29.97 and 59.94 (cameras show it with “;”). The file’s is respected, and you can tick or untick it on each camera.

A checklist for the recording

1. 1Keep every camera’s own audio on.
2. 2Start every camera before the conversation starts, and stop them after it ends.
3. 3Don’t trim the files before the edit: give OnAirCut the whole recording.
4. 4If your cameras support it, set the same timecode on all of them.