Let's assume your video recorder (phone, camera, etc.) died while recording an MP4 (or MOV or 3GP ... they are mostly the same container format). If you try to read/analyze it with ffmpeg
, it'll tell you that "moov atom not found". The problem is that recorders put the most important part of the video (this so called moov atom
) at the end of the video file. It contains the index of the video and the metadata (like codec, etc.). So everything that a video player needs to know to be able to play it back. The reason for this is simple: while you're recording the video, you don't have the full index yet. You only have it, when the recording is finished. And you don't know in advance how long the video is going to be so you cannot simply reserve some space for the index at the start of the recording.
There're tools that let you move the moov atom from the end of the file to the start so internet connected players can start playback instantly when they start downloading the file (instead of having to wait til the entire file is downloaded). However this won't help you if your moov is missing altogether.
It'd seem that this problem is more widespread and there're lots of apps that can help you fix such broken files. Unfortunately that's not the case. Actually I've found only a single app called Grau's Video Repair Tool
. It's a bit costly for the average user, but you can buy the license for the repair of a limited number of videos significantly cheaper. However the tool's earlier versions were freeware and if you happen to find a copy online
), you can still use it.
Obviously the tool has seen quite a few versions since then, so if the free version does not work, you can still try the current demo version and if it works, you can buy a license for recovery of 5 video files. (P.S.: the free version pretty much works for me ... at least with the broken videos created by my phone's camera app in case it crashes for some reason before the recording is finished)
P.S.: obviously the free version of Grau's Video Repair Tool is hard to come by these days. The official site has removed it long ago and various links to copies become invalid after some time. You should search for the filename that was originally used to publish it: "videorepair1.5.zip"
This dropbox URL
(Google just gave me while searching for alternative locations of the utility) might survive for a longer time.