By Pritibhukhan Borah, Computer Science Engineer · Last updated: 2026-11-02
Match the symptom to the cause
| Symptom | Common cause | What to try |
|---|---|---|
| Length shows 0:00 or is far too short | The index that records frame timing is missing or damaged | Rebuild the index |
| Cannot skip forward or back | No usable index, so the player cannot jump to a position | Rebuild the index |
| Picture plays, no sound | Player does not support the audio codec, or the track is missing | Try VLC; check the audio codec |
| Sound drifts out of sync | Variable frame rate, editing, or a mismatched reference | Try another player; re-check the reference |
| Sound only on the repaired file is missing | Audio was not AAC-LC, or the reference had a different audio format | Use a reference with the same audio settings |
Wrong length or 0:00
A player works out the duration from the index, not by reading all the frames. When a recording is interrupted, that index is often never written, so the player has nothing to add up. The footage is usually still in the file. Rebuilding the index restores the duration and the seek bar.
Cannot seek
Seeking means jumping to the nearest keyframe. The index lists where those keyframes are. Without it, a player either refuses to seek or has to scan the whole file first. Files that are still being written or downloaded behave the same way.
Video plays without sound
First check whether the file ever had audio. Some cameras and screen recorders skip it. If it did, the likely cause is the codec: players built into some systems do not decode formats such as AC-3 or DTS, while VLC usually does. When repairing an MP4 or MOV with this tool, sound is kept only for AAC-LC, the format nearly all phones and cameras use, and it needs a reference with the same audio settings. For other audio the video is still repaired and the log says the sound was left out.
Sound out of sync
Small drifts often come from variable frame rate, which phones use to save space, or from editing. A repair copies the audio as recorded, so the original timing is kept. If the sync is wrong only after repair, the reference probably differs from the damaged file, for example a different frame rate. Choose a new reference recorded in the exact same mode.
Related
Frequently asked questions
Why does my video show 0:00 but is hundreds of MB?
Because the data is there but the index with the duration is not. That is the case a repair is designed for.
Can a player fix missing sound by itself?
Not if the file has no audio track. If the audio codec is unsupported, a different player such as VLC often plays it.