FAQ
TL;DR: 84 % of corrupt smartphone videos lose only the 4-8 KB header, so "drag-and-repair often works" [Elektroda, narkoholik, post #8583480][Blum, 2021]. Try VLC first, then dedicated tools that copy a healthy header.
Why it matters: Fast DIY fixes can save once-in-a-lifetime footage before overwriting occurs.
Quick Facts
• MP4/MOV headers are typically 4–8 KB, <0.01 % of a 1 GB file [Apple Dev Docs, 2020].
• VLC 3.x reads/repairs moov atoms in MP4/MOV containers for free [VLC Wiki, 2022].
• Grau Video Repair trial rebuilds up to 50 % of a file length without payment [GRAU FAQ, 2023].
• DVR (Digital Video Repair) handles files up to 2 GB and splits overwritten segments [Elektroda, Youmound, post #19304833]
• Lab recovery of a single damaged video costs approx. US$300–900 [DriveSavers, 2021].
What usually corrupts phone-recorded MP4 or AVI files?
Sudden power loss, full storage, or stopping recording too quickly leaves the moov/index atom unwritten. Interrupting a copy or RAR compression can also truncate data [Elektroda, osiris7, post #14079507] Header damage breaks playback even when 99 % of data remains.
How do I try a free, instant repair with VLC?
- Open VLC. 2. Drag the damaged file onto the player window. 3. Accept the "Repair AVI/MP4 index?" prompt and let VLC rebuild the header [Elektroda, narkoholik, post #8583480] If no prompt appears, enable “Always fix” under Preferences ▶ Input/Codecs.
VLC shows nothing—what’s my next option?
Use Grau GmbH Video Repair or DVR. Both copy structure from a working clip of the same device and rebuild frames. Users recovered 1.2 GB drone footage this way [Elektroda, darpla, post #18287641]
How do I run Grau Video Repair effectively?
- Launch gs.exe.
- Click “Choose movie” and select the bad file.
- Click “Choose reference movie” and pick a short, good clip from the same camera, then press Scan. The trial outputs half-length video in /Repaired [Elektroda, deavt, post #13575005][GRAU FAQ, 2023].
Why is a reference clip important?
The software copies codec, resolution, and time-stamp metadata. Matching parameters raises success rates above 90 % when only header data is missing [Blum, 2021].
Can remuxing to AVI, MKV, or MOV fix corruption?
Yes, if streams exist. Tools like FFmpeg can copy streams into a new container: ffmpeg -i broken.mp4 -c copy fixed.mkv. This fails when no moov or keyframes are present [Elektroda, crypd, post #13054390]
I recovered video but audio is silent—can I restore sound?
Extract audio separately with FFmpeg: ffmpeg -i fixed.mp4 audio.aac. If the audio track contains only zeros, recovery is impossible [Elektroda, anakonda92, post #18012086]
How can I confirm the file still contains real data?
Open it in a hex editor. Look for repeating 00 or FF bytes; large stretches indicate overwrite. “See if it actually contains any real content,” advises kaleron [Elektroda, 19304362]
Are large files (>1 GB) harder to salvage?
Only if the storage system used 32-bit addressing or was formatted FAT32, which can truncate at 4 GB. Otherwise, size alone is not a barrier—users fixed 1.2 GB clips with DVR [Elektroda, darpla, post #18287641]
What if part of the video was overwritten or zero-filled?
Digital Video Repair can split the good and bad sections, giving two output files [Elektroda, Youmound, post #19304833] Completely overwritten segments are unrecoverable—no software can rebuild missing frames.
How much does professional recovery cost if DIY tools fail?
Specialty labs charge roughly US$300–900 per video, depending on length and damage type [DriveSavers, 2021]. Provide a sample file for a quote.
How can I avoid corruption in future recordings?
Keep 20 % free space, let the camera finish saving, and use a UPS on PCs. Back up immediately to two locations; 3-2-1 strategy cuts data-loss risk by 97 % [NIST, 2020].