Audio out of sync in editing: why it happens and how to fix it
If the audio is off by the same amount for the whole clip, the start is not lined up exactly. If it is exact at the start but late by the end of the take, that is clock drift: the camera and the recorder count time at slightly different speeds. If the offset wanders, a phone's variable frame rate is often to blame. MultiSyncer Studio measures the offset to the sample, corrects drift and flags variable frame rate clips in advance.
Why the audio does not match the picture
| What you see | Cause | What to do |
|---|---|---|
| The audio is off by the same amount for the whole clip | The start is not lined up exactly | Sync again by sound, timecode or slate |
| Exact at the start, late or early by the end | Clock drift: the camera and the recorder count time at slightly different speeds | Resample the sound to the camera's speed |
| The offset wanders through the clip, often on phones | Variable frame rate (VFR) | Find these clips before the edit and check them separately |
| The audio falls behind or runs ahead evenly, like drift | The sound was recorded at a different sample rate, for example 47,952 Hz instead of 48,000 Hz | Check the sample rate of the recorder files |
How to tell which cause it is. Listen to the camera sound and the recorder sound together at the start and at the end of a take. The same echo everywhere: the start is off. No echo at the start and it grows towards the end: drift.
Where built-in sync falls short
| Task | Built-in sync of an editing app | MultiSyncer Studio |
|---|---|---|
| A long take | Finds one offset for the whole clip and does not change the speed of the sound, so drift stays. | Measures the speed of every device and resamples the sound to the camera's speed into new WAV files. |
| How far off it is | Sync errors happen and you have to find them yourself: the app does not show them clearly. | The offset in milliseconds, samples and frames is recorded in the sync log. |
| Phones and VFR | A variable frame rate clip is noticed when the sound starts to slide. | The footage check flags variable frame rate (VFR) clips right after the copy. |
How to fix it in MultiSyncer Studio
Sync the whole shoot
Press “Synchronize”: the sound of every clip is compared with the others and the offset is measured to the sample. More in the article “How to sync audio and video”.
Turn on drift correction on export
The app measures the speed of every device and resamples the sound to the camera's speed into new WAV files next to the export. The start of a long clip is taken from the drift line, not from the first match. The original files are not touched.
Check the doubtful clips
Variable frame rate clips and clips with no shared sound are marked. Listen to them A/B and, if needed, adjust the position: nudge by a frame, lock, “Sync to…”.
Synchronization complete
Needs review
F002 · IMG_0412.MOV · by file time
F002 · IMG_0415.MOV · by file time
Different recording speed
Recorder: 40 ppm, 96 ms by the end