Manatee

Recovered videos that will not play after an SD card rescue

· 7 min read

You ran recovery software on a formatted or failing card, it found your clips, and now most of them will not open. QuickTime says the file is not compatible, or the duration shows as zero, or a clip plays for a few seconds and stops. This is normal for recovered video, and it is often, though not always, fixable. The most common fault, a missing index, is also the most repairable one.

Videos come back from a rescue in worse shape than photos because of how they are laid out on the card and how recovery tools find them.

How recovery tools find files

When a card is formatted, or files are deleted, the list of where each file lives is cleared, but the data itself usually stays on the card until something new is written over it. Recovery tools scan the raw card for the recognizable opening bytes of known file types, such as the header at the start of an MP4 or a JPEG, and copy out the data from that point. This is called carving.

Carving works well for a file stored in one continuous run. With video, it has two weaknesses:

  • Where does the file end? Without the directory, the tool has to guess. It may stop too early and cut off the end, or run on into whatever follows.
  • Is the file in one piece? A long clip on a card that has been filled, emptied and refilled may be stored in several fragments. A tool that assumes one continuous run will stitch in whatever sits after the first fragment, which may be part of a different clip.

Why the index matters so much

MP4 and MOV files keep the picture and sound in one block and a separate index, called the moov, that says where every frame is. Many cameras write the index at the very end, once recording finishes. If carving stops short, or the end of the clip sits in a fragment the tool never found, the frames are all there but the index is not, and no player can make sense of them.

That is the single most common reason a recovered clip will not open. It is also good news, because the frames themselves are intact and an index can be rebuilt from them. A file that copies to an external drive and arrives broken shows the same structure from a different angle.

Camcorder formats such as MTS and M2TS are streams with no index at all, so a carved MTS clip often plays as far as its data goes and then stops.

First, protect what you have

  1. Stop using the card. Do not format it or record to it until you are sure you have everything you can get.
  2. Keep the recovered files on a different drive from the card, and never recover onto the card itself.
  3. Work on copies. Anything you try should write a new file and leave the recovered one alone, so a failed attempt costs nothing.
  4. Consider a second pass. If the recovery tool offered a deeper or slower scan and you used the quick one, run the deeper scan into a new, empty folder. It may find clips or fragments the first pass missed.

Triage the recovered files

Recovery folders fill up with numbered files, many of them useless, so sort first. In Finder, switch to list view (Command-2) and click the Size column.

  • Zero bytes or a few kilobytes. Fragments or false matches. There is nothing in them to repair.
  • Sizes that make sense. A clip you remember as several minutes long should not be a few megabytes. Files roughly the right size are the ones to work on.
  • Many files of exactly the same size. Some tools cap a carved file at a fixed length when they cannot find its end, so identical sizes can mean truncated clips.

Then check each promising file. Press Space for Quick Look, then try QuickTime Player. Select the file and press Command-I; a duration of zero, or no duration at all, points to a missing index. If a file has the wrong extension, or none, Terminal’s file command reports what the data really is:

file recovered-0042.mov

How to check whether a video file is corrupted goes through more tests if you want them.

Repairing the clips that will not open

Rebuilding a missing index from the frames that survived is a repair job, and Manatee does it in Repair mode. Drop a recovered clip on the menu bar icon or into the window. Manatee scans the frames that are present, rebuilds a playable file around them, and writes the result as a new copy beside the recovered file, which it never modifies. It reads the formats cameras use, including MP4, MOV, MTS, M2TS and AVI, and everything happens on your Mac, which matters when the footage is private.

Each file gets one of three honest outcomes:

  • Fixed: the whole clip plays.
  • Partial: some of it plays, such as the first eleven minutes of a longer recording. Partial recovery explained describes what that means in practice.
  • Not fixable: nothing usable was found.

Set expectations by the kind of damage. A clip whose data is continuous but lost its index is the best case. A clip that had another file’s data stitched into it can at best be Partial: the stretch before the foreign data can be saved, and what follows may not be. Anything written over since the card was formatted is gone, and no tool can bring it back.

To be clear about what Manatee is not: it is not a recovery tool. It does not scan cards for deleted files. It works on the files your recovery software has already pulled off.

Photos from the same rescue

JPEGs are much smaller than video and are usually stored in one piece, so they survive carving better. When one shares space with a fragment of something else, it tends to come back half gray or with colors shifted from some line down. A JPEG that shows half gray explains what can be done with those.

Next time

  • Copy clips off the card before deleting anything, and check that the copy is complete. Verifying a file arrived intact shows how.
  • Format cards in the camera rather than on the Mac, so the card is set up the way the camera expects.
  • Retire a card that has thrown an error once. Cards are cheap; footage is not.

Questions

Why do the recovered files have numbered names instead of the originals? File names lived in the directory that was cleared. Carving finds data, not names, so the tool invents names as it goes.

A recovered clip plays but glitches or freezes in the middle. Can that be fixed? Partly. A repair pass can rebuild the file’s structure around the frames that survived, but frames that were damaged or replaced by other data cannot be restored. A video that freezes partway while the audio keeps playing covers that symptom.

Is it worth running the recovery again? If the first pass was a quick scan, yes. Run the deeper scan into a new folder on another drive, and compare what it finds with what you already have.