You can now repair corrupted and damaged video files (mp4, mov, 3gp) online with this free video repair tool. https://repairvideofile.com/

It is very easy and staright forward to use, all you need to do is to upload the corrupt video and it would automatically be repaired.

how about the app to repair corrupt audio files?

The SysCurve Video Repair Tool is a robust software designed to repair corrupt and damaged videos across a variety of formats, including MP4, MOV, AVI, and more. It features the ability to repair multiple videos simultaneously and provides an advanced repair option using a sample file from the same device for severely corrupted files. Users can preview repaired videos before saving and the tool supports videos from various devices like iPhones, drones, and DSLRs. It's compatible with Windows OS and tailored for both professional and casual use. For further details, please visit: https://www.syscurve.com/video-repair-tool.html