cgsecurity.org

Data copied back from RAID1 HD (NAS Synology) using Photorec.
All data have the attribute mp4. Some of the mp4 files are playable with a player, some are not. Player does not start playing.

Does anyone have a solution

The performance of Photorec degrades when your disk ist fragmented.
Try other commercial solutions instead that will try to evaluate remaining metadata on your disk.