The timecode slate: what those numbers do after the clap

A timecode slate, sometimes called a smart slate, displays running timecode on an LED face. It is filmed at the head of every take, so the picture carries a readable stamp of the same clock the sound recorder is writing into the WAV file.

Jam syncing

At the start of the day, the slate is jammed: a cable from the master clock, usually the sound recorder, loads the current timecode and the slate then free runs on its own oscillator. Cameras are jammed the same way. Everything is now telling the same time.

Why drift happens

• Every crystal oscillator runs slightly fast or slow, typically a frame or two over several hours.
• Temperature changes push oscillators further apart.
• Batteries dying and swapping devices can reset or corrupt the clock.
• Re-jam every few hours, and always after lunch, to keep drift inside a frame.

Why the clap survives

The clap is the fallback. If timecode fails, is jammed wrong, or a camera drops it entirely, the clap gives a single frame accurate transient that can be matched by eye and ear. It also carries scene and take information for anyone reading the rushes without metadata.

Where the timecode lives in the audio file

In a BWF file, the start time is written as a sample count in the bext chunk, alongside scene, take and note fields. Software reads that number and places the file on the timeline automatically. If the number is missing or wrong, sync falls back to waveform matching or the clap.

Drop a WAV into the inspector here to read its timecode, sample rate and metadata locally, before you troubleshoot a sync problem in the edit.