Compare the original recording, the CastCuts source preview and the downloaded clip at matching moments. Note whether the offset stays constant or grows through the episode. Fix a faulty source in an external editor before uploading it again. Caption timing and lip synchronization are different problems; rewriting caption text does not move the audio track.
Locate the first version that loses sync
Use headphones and choose an obvious visible sound, such as a clearly pronounced word or a hand clap. Compare a passage near the start, middle and end of the original recording in a local player. Then inspect the source preview and downloaded clip. If only one browser playback appears delayed, test the saved file in another player before changing the source. Record the exact passage rather than relying on a general impression.
Distinguish a constant offset from progressive drift
A similar delay everywhere suggests a different repair from a gap that becomes larger over time. When camera and microphone recordings were combined externally, check their alignment and project settings there. For a constant offset, your editor may allow shifting the audio track. For progressive drift, investigate the recording and export timing first. CastCuts does not expose a separate audio-slip, time-stretch or microphone synchronization control.
Prepare and test a corrected source externally
Vimeo’s troubleshooting guidance identifies out-of-sync source files and variable frame rate as possible causes. That is a diagnosis to investigate, not proof that every variable-rate recording is faulty. Inspect your source’s properties and your editor’s recommended workflow. If necessary, make a constant-frame-rate working copy and verify it locally. Keep the original and avoid blindly changing several audio and video settings at once, which makes the successful fix harder to identify.
Render the problem passage before rebuilding clips
Upload the corrected recording as a new source and select a short passage where the mismatch was obvious. Recheck timestamps if the new export changed the beginning or duration. Download a test render and compare lips with speech; then review the caption timing separately. Existing rendered MP4s retain their original content, so prepare new renders for the corrected source. Keep working copies and exports before CastCuts media expires.
A fictional interview that drifts late in the episode
Illustrative example. The people, recordings and results described here are fictional.
A producer notices that a guest appears synchronized in minute two but visibly late in minute 35. The same drift occurs in the original meeting export, so the problem predates clipping. They prepare a corrected working copy in their editor and test a passage near minute 35. Only after the downloaded clip is synchronized do they recreate the other selected moments from the new source.
Check the late passage that exposed the problem, not only the corrected file’s opening.
Check before you finish
- The original, source preview and downloaded clip are compared at matching speech.
- A constant delay has been distinguished from drift that grows over time.
- The repaired source works at the beginning, middle and end.
- New renders pass both lip-sync and separate caption-timing checks.
Practical questions
Can caption editing fix delayed audio?
No. Caption words, their display timing and the audio/video relationship are separate. Fix the source when its sound and picture are misaligned.
Does variable frame rate always cause drift?
No. It is one possible cause to investigate when symptoms fit. Compare the source and players first, then use the external editor’s documented repair workflow.
Will rendering again repair the same faulty source?
Do not count on it. Locate the mismatch and verify a corrected source first. Repeating a render without changing the cause can reproduce the same problem.
Use this workflow in CastCuts
Test a prepared source with a short video clip
CastCuts selects continuous 1–90 second excerpts and exports 9:16, 720 × 1280 H.264/AAC MP4 files. Automatic transcription and transcript-based suggestions support English and require review. Free exports include CastCuts branding; Pro removes it from new renders for $9 USD/month, with the same processing and storage limits. Episode media is retained for 24 hours. Keep your originals and download finished clips before expiry. Publishing is manual.