Why Recovered Videos won’t Play

Many users of Treasured and MP4repair.org are very surprised to discover that their videos, after being recovered or undeleted by data recovery tools, still cannot open or play!

After having burnt days trying several tools and spent money on the most promising one, their recovered video files are still corrupt and they finally come to us because only our diagnostics tools Treasured (or MP4repair.org) can preview them and give them some hope.

Why does it work for my PDFs but not for my videos?

Data recovery tools are usually good at undeleting small files, like PDFs, Word and Excel documents, or low-res images. But as file size increases, the chances of recovery plummet.
Even for JPEG pictures in the 2 – 5 MB range, about 15% of files appear missing or corrupted.

For video files, whose size is usually in the hundreds of MB, and even in the tens of gigabytes for post-production formats, the chances of recovery are almost zero.

The reason is FRAGMENTATION: In your disk, everything is stored in fixed-sized “blocks”, like the shelves in the picture below. But if the file is big, it will not fit in one shelf.

Video files occupy many shelves. If the file is really big, let say 20 shelves, it’s not even possible to store it in contiguous shelves. In picture below, it’s obvious that really big files will end up spread over different walls.

Why Fragmentation Kills Recovery

Fragmentated files are split into several pieces, each piece being stored at a different place. Data is no longer contiguous.

This is not a problem for the operating system, that knows where those pieces are stored. But after a file deletion or a disk failure, this “map” also disappears and the file is now lost in the middle of thousands of shelves.

All data recovery tools (except high-end forensics tools, more about that below) use simple file carving techniques to recover deleted data.

Most common technique is Header/Footer carving. It consists in identifying the beginning of a file of a certain type, using a signature or pattern. AVI files, for example, start with RIFF word. MP4 files have a movie atom at the end of the file (footer) that can easily be detected using pattern matching.

Once a header and a footer are found, the data recovery program assumes that all data in between is part of the video file. This will only be true is the file was stored in one piece, without fragmentation.

This rarely happens. Even in disks with plenty of space available, fragmentation often happens as a side effect of video recording. For example, XDCAM cameras write as the same time several files (MP4, BIN, PPN) and this causes a systematic fragmentation of the MP4 video file.

Alien Data

Therefore, any fragmented video file recovered will contain “alien data”.
This will cause the following problems, from less serious to more serious:

  • Glitches in video and audio.
  • Possible crashes during playback
  • Missing footage, footage from different clip inserted in video
  • File no longer opens due to inconsistency of video container
  • File not even recovered if software doesn’t find footer

Recovery is not Repair

Data recovery tools are very good at restoring small files of many different formats, by identifying superficial features of the data (header signatures, footer patterns) and assuming that the file is not fragmented.

But this assumption is not true for video files. The only effective technique that can be used to recover fragmented files is called “deep carving”.

Tools implementing this technique are very few, very specialized, more expensive, slower, and are based on probabilistic algorithms specific to the video and audio formats to recover.

  • Recovery tools achieve good results on small files, but not on videos, due to fragmentation.
  • Recovery tools can’t actually repair fragments of video files, because they can only identify generic and superficial file features
  • Video Repair tools are specialized. They are built to repair one type of videos only,for example Canon EOS 1080p24 or XDCAM 720p30.
  • Video Repair tools identify video frames and audio blocks deep inside the file and re-index them into a playable video.

This is the reason why our repair service works when other generic recovery tools don’t: We build specialized tools that can assemble the puzzle, fit the parts of the disk together to restore a functional video file.