Protect the recording you have
Make a separate copy before trying to repair the file. Leave the original name and contents intact, and choose a new output name for every attempt. Keep the untouched original so you can return to it if an attempt makes the copy less usable.
If the file is still on the recording device, check whether the app or device has its own completion or recovery option. Also check whether you have a second copy that was saved before the interruption. A complete copy is more useful than a repair of an incomplete one.
Renaming .mov to .mp4 changes the filename, not the container information inside it. A different player may be worth trying on a copy, but a player cannot make missing source data appear.
What the error does—and doesn’t—mean
In a regular MP4 or MOV, the movie index describes how recorded media should be read, including its tracks and timing. A recording that stops before finalization may leave media data without the information needed to use it. The message can also appear when that information is damaged or unreadable.
The important question is whether the media data you need is still present. Rebuilding an index can help make existing data readable. It cannot restore frames or audio that were never written, were overwritten or are no longer in the file.
If the file is still readable
If you already use FFmpeg, inspect a copy before trying a remux. This example reads container information and does not write to the recording:
ffprobe -v error -show_format -show_streams "recording-copy.mp4"Look for codec_type=video and the expected codec_type=audio entries. These show which streams the probe can identify; they do not test the entire recording. If the output ends with moov atom not found, the probe could not read the movie index.
When the streams are readable but an editor rejects the file, a remux may help. This command attempts to copy all streams into a new container without re-encoding them:
ffmpeg -n -i "recording-copy.mp4" -map 0 -c copy "remuxed-copy.mp4"-n refuses to overwrite an existing output, and -map 0 includes every input stream. If the output container rejects one of those streams, inspect the reported codec or track before changing the command; silently dropping an audio track would give you a different recording.
If the input cannot be opened because its movie index is missing, the command may stop at the same error. Repeating it with a different output name will not rebuild that index.
FFmpeg’s +faststart option relocates an existing movie index to the beginning for playback. It is not a general way to reconstruct an absent index. See the FFmpeg MOV/MP4 format documentation.
When a healthy reference matters
A recovery path may need recording parameters that the damaged file no longer provides. A healthy reference from the same camera, phone or app can help, but “another MP4” is not a meaningful match.
Use a healthy clip made with the same recording setup where possible: codec, resolution, frame rate, audio codec, sample rate, channel layout and number of audio tracks. If settings changed between recordings, say so rather than assuming the new clip matches.
A short recording made now may be useful if you can reproduce the original settings. Do not damage that clip on purpose. Do not borrow an unrelated file as a template. A readable reference can still be a poor match; a reference that cannot itself be read needs to be replaced.
What a MendVid attempt involves
MendVid lists a repair-attempt fee of US$9.99 per video, with applicable tax shown at checkout. New purchases were not open when this guide was reviewed on 31 October 2026; check the repair page for current availability. When purchases are open, review the terms and confirm payment before uploading the file for repair. Both the repair attempt and its result preview happen after confirmed payment.
The repair workflow tries methods suited to the file and checks the outputs for video decoding, audio tracks and timing. Results distinguish recovered, partial, reference-required and failed states. A file that was written but fails those checks is not presented as a successful repair.
If a matching reference is requested, it stays on the same paid job without another fee. After confirmed payment and a repair attempt that produces a recovered or partial result, you can review a watermarked sample made from that result. The watermark is burned into the sample’s pixels.
Check more than “it plays”
For a real output, compare what you can against the recording you expected. Look at the opening, important middle sections and ending. Listen to each expected audio track. Check whether the duration makes sense and whether sound still matches the picture.
Clean decoding shows that the output can be read. You still need to check whether the scenes and sounds you expected survived and whether sound stays aligned with the picture. A shortened video or a missing audio track should be reported as partial recovery.
Some repair paths rebuild the video clock by re-encoding video while copying audio. Check the result’s re-encoding notice: that output is not a lossless video remux. Repair also does not sharpen blurry footage or create details that were never recorded.
Reviewed 31 October 2026. The linked FFmpeg documentation explains the container options; the recovery checks and paid-attempt terms above describe MendVid. See also the guide to interrupted OBS recordings for ordinary and Hybrid formats.