5 min read
How to convert camera audio to WAV without breaking sync
Camera audio is the reference that gets a day of rushes in sync. Extracting it should change nothing about it.
Whether it is a scratch track from an on board microphone or a proper feed from the mixer, the audio inside a camera file is often the fastest way to line up picture and sound. Getting it out as WAV takes seconds when the tool respects the source.
Read the source before converting
Camera files vary: 48 kHz 16 bit PCM stereo from a mirrorless, 48 kHz 24 bit four channel from a cinema camera, compressed AAC from a phone. Extract at whatever the container reports rather than at a fixed preset.
What breaks sync
- Resampling to 44.1 kHz, which changes the duration relative to picture.
- Trimming to the first audio frame, which shifts the start point.
- Summing multichannel camera audio to stereo, which loses the isolated feeds.
Multichannel camera masters
Cameras that record four channels usually put the mixer feed on 1 and 2 and the on board microphones on 3 and 4. Extract as multichannel, then split so each feed is a separate mono file you can enable or mute independently.
From extraction to sync
Once the WAV is out, sync by timecode if the camera and recorder were jammed, or by waveform against the sound department files. The camera track then becomes a guide you can mute after the dialogue stems are conformed.
Local extraction
The extractor here reads the container header, reports the native rate and depth, and writes a WAV with those values. Everything happens in the browser, so unreleased footage never leaves the machine.