How to fix audio that only goes out of sync partway through
Tell Vizard Agent the timecode where the sync goes wrong and that it was fine before it. It compares the finished frames against the source to locate where the two diverge, measures the exact offset that opened up, finds the structural cause, and rebuilds from there rather than nudging the whole track.
What do you type into Vizard Agent?
Give the timecode and the fact that it was correct up to that point. Without the second half, a reasonable reading is that the whole track needs shifting, which will fix the last three minutes and break the first seven. Roughly where you noticed it is enough.
Prompt
What does Vizard Agent actually do?
Audio that is out of sync from the first frame is a simple offset. Audio that is fine for seven minutes and wrong afterwards points to a place in the edit where the picture gained or lost time and the sound did not, so Vizard Agent diagnoses before it adjusts anything. In the session behind this article it:
- Rendered the assembled cut of an eight-and-a-half-minute video, with all its reframes and push-ins, and verified the base timeline frames to locate missing seconds.
- Had the finished edit watched through for sync problems, then compared the final frames against the source to locate the drift, and ran the comparison again across a different span to confirm it.
- Measured the exact video offset after a freeze section, which was the culprit. Holding a frame is a picture-only operation, so everything after it was offset by the same amount.
- Rebuilt the assembly with the corrected sync, verified the fix on the rebuilt file and reviewed the rebuilt tail frames specifically.
- Extracted dense frames across every fixed transition and reviewed them all frame by frame, because once one structural feature caused drift, every other one was a suspect.
When does this not work well?
Some drift is not in the edit at all. It is baked into the recording and grows from the first frame, as with phone footage at a variable frame rate or a sample rate mismatch. That needs a different fix, and Vizard Agent will tell you which you have. Offsets below a frame or two aren't measurable, and without the source there is nothing to compare against.
Common questions
Do I need the exact timecode? No. Roughly where you noticed it is enough for Vizard Agent to start.
Can it just nudge the audio? It can, and Vizard Agent will tell you why that usually makes things worse.
What causes it most often? An operation that changes the picture's duration without changing the audio's. Vizard Agent names it.