Many MP4's are damaged

[Dual]

After migrating a large number of MP4 files from one drive to another, they show up as unplayable in VLC. Specifically they show a duration of 0:00. I've been searching around on the net about this, and found a suggestion that I use VLC to rename the files as AVIs and then force repairs. That has not worked. In my research I see many offers of commercial software offering to fix these files, but they all seem to be from no-name vendors and I am very reluctant to download this software.

Is there any hope for recovering these files? A surprising number were damaged in the migration (Carbon Copy Cloner V 5.1.28 (6213) process.

MacOS 10.14.6 Mojave
VLC 3.0.17.3

Thank you

[JohnyC]

If you're in doubt of downloading software, you can use an online video repair tool, such as restore.media. However, regardless of the tool you use, you will probably need a working reference mp4 file. Video repair tools work by extracting valid metadata headers from healthy files and then replacing the ones in the corrupted files. If you don't have a reference file, you can try asking restore.media's support to check if they have one. Also, what's the size of the files? It may actually appear that the files are empty due to some malfunction during the transferring process. In this case, there is nothing to repair, unfortunately.

[fkuehne]

Sadly, this sounds a lot like a corruption problem with the migration that cannot be solved by VLC.

Renaming media from MP4 to AVI will not solve the problem. While indeed we offer a repair mechanism for one singular, very isolated, very typical problem of AVI files, we do not offer any such features for any other container format. Renaming the file will not change that. It would be the equivalent of putting a BMW sticker on your Honda and asking your BMW dealer to fix it.

[Dual]

Thank you very much for this. I definitely have found these files to be unrecoverable period
I really appreciate your checking on this.