6 min read
Sync sound: keeping dual system audio locked to picture
Recording sound separately from picture is standard practice. Everything about sync sound is designed to make those two files meet again.
Dual system means picture goes to the camera and audio goes to a dedicated recorder. You get better preamps, more channels and proper metadata. You also take on one obligation: the two must line up perfectly in the edit.
Three ways to sync
- Timecode: recorder and camera share a clock, and the NLE matches takes automatically.
- Waveform: software compares the camera scratch track with the recorder file and aligns them.
- Clapperboard: the visual and audible reference that saves you when the other two fail.
Always record a scratch track
Whatever the camera microphone sounds like, keep it running. Waveform sync depends on it, and it is the only thing that recovers a take when timecode was not jammed or the slate was missed.
Where drift comes from
Two devices free running on internal clocks slowly separate. Jam sync at the start of the day and again after lunch, or use a lockit box. A mismatch of a few frames across a long take is the classic symptom of a clock that was jammed twelve hours earlier.
Sample rate is the other clock
If the camera records at 48 kHz and the recorder is set to 44.1 kHz, files will drift progressively even with perfect timecode. Confirm both devices are at the project rate before the first take, and check a file after the first setup.
You can verify sample rate, bit depth, channel count and embedded timecode in our audio inspector, and convert anything that is wrong with the sample rate converter, all locally in the browser.