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Moov atom not found: what it means and how to fix it on a Mac

· 7 min read

“Moov atom not found” means the video file still has its picture and sound but not its index, the moov atom that tells a player where every frame is and how long the recording runs. Cameras and recording apps write that index last, at the moment recording stops cleanly, so a dead battery, a card pulled out too early or a recorder that crashed leaves a file full of media that nothing can find its way around. A repair can often rebuild the index from the frames themselves, but only from what is in the file: how much comes back depends on what the recorder managed to write before it stopped.

Where you see the message, and what a Mac shows instead

The exact words come from ffmpeg, the open-source media engine inside many converters, editors, players and video upload sites. In Terminal the error looks like this:

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f967b904780] moov atom not found
GX010042.MP4: Invalid data found when processing input

Apple’s own apps never use the phrase. The same file on a Mac looks like this:

  • QuickTime Player refuses to open it, with a message such as “The file isn’t compatible with QuickTime Player” or one saying the movie can’t be opened and the file may be damaged. Neither mentions the index.
  • Finder shows a generic icon with no thumbnail, and pressing Space gives Quick Look nothing to preview.
  • Get Info (Command-I) shows a believable size, often hundreds of megabytes or several gigabytes, but the More Info section has no Duration and no dimensions. Those values live in the index, so with the index gone there is nothing to show.

One check that does not help is Terminal’s file command. We cut the index off a test MP4 and file still reported “ISO Media, MP4 Base Media”, because the header at the very start of the file was untouched. A normal-looking answer from file does not mean the index is there.

Why the index goes missing

An MP4 or MOV is built from labeled blocks called atoms (or boxes). The big one, mdat, holds the compressed frames and grows as the camera records. The moov atom is the table of contents: where each frame sits, how big it is, when it plays, and the settings a decoder needs before it can show the first picture. The recorder cannot write that table until it knows how the recording ends, so it writes it last.

Anything that stops the recorder before that final step leaves media with no index:

  1. The battery died mid-recording, on a camera, drone, dashcam or phone.
  2. The card was pulled, or the camera switched off, while the card light was still blinking.
  3. The card or the phone’s storage filled up and the recorder could not finish.
  4. A screen recording or a recording app crashed, or the Mac restarted, before you pressed stop.
  5. A copy or download ended early. The index is often the last thing in the file, so it is also the last thing to arrive.

Video exported for the web often has the index at the front (a “fast start” layout), which is why a truncated web download can play up to the cut. Most cameras cannot do that while they are still recording.

What can realistically be rebuilt

The frames are usually still there. A repair scans the media data, works out where each frame starts and ends, reconstructs the timing, and writes a new index. Whether that works, and how completely, depends on things you cannot change after the fact.

  • The decoder settings. H.264 and HEVC video needs a short set of parameters before the first frame can be decoded. Many recorders keep those only in the moov atom, not next to the frames. Some repeat them inside the stream as they record; others never do. When they existed only in the index that was never written, the file no longer contains what a decoder needs to read the frames, and that is a common reason a file ends up Not fixable.
  • The sound. In an MP4, AAC audio frames carry no markers of their own, so they are harder to pick out of raw data than video frames. A rebuilt file can come back with the picture whole and the sound shorter, or missing.
  • The last few seconds. Whatever the recorder was still holding in memory when the power went never reached the card. Expect the end to fall slightly short of where you stopped.
  • The size. A file holds what it holds. If it is a fraction of the size the recording should be, only that fraction is in it. Video file is 0 bytes or shows the wrong length shows how to estimate what is inside, and what to do when the file is empty.

Clips pulled off a formatted or failing card add another problem, because the recovery tool may have stitched pieces of different clips together. Recovered videos that will not play after an SD card rescue covers those.

Before you repair anything

  1. Look for a complete copy. Check Photos on the phone it came from, or a cloud folder or camera app that synced it. A good copy beats any repair.
  2. Leave the card alone. Do not format it or record to it until you are sure you have everything you need from it.
  3. Copy the file to the Mac’s internal drive and work on that copy, never on the only copy sitting on a card.
  4. Skip the quick tricks. ffmpeg -i broken.mp4 -c copy fixed.mp4 fails with the same “moov atom not found” error, because ffmpeg cannot read the input without an index. Renaming .mp4 to .mov, or the reverse, changes nothing either; the two formats share the same structure.

Repairing the file with Manatee

Manatee has a Repair mode for this. It works from the damaged file alone and can only return what that file holds. It runs entirely on the Mac, with the repair engine bundled in the download, so the footage is never uploaded anywhere.

  1. Open Manatee. Every feature is free for the first 24 hours, with no card and no email.
  2. Drop the file into the window or onto the menu bar icon, or right-click it in Finder and choose Services > Fix with Manatee.
  3. Wait for the job to finish. Progress shows in the job list. A long 4K file takes longer because the whole stream has to be scanned.
  4. Read the outcome. Fixed means the recording plays. Partial means part of it does, for example the first eleven minutes of a longer recording. Not fixable means no usable video could be rebuilt.
  5. Open the repaired file, which is written as a new copy beside the original.

Manatee never modifies the original, so a Not fixable result costs you nothing: the broken file is still there, exactly as it was. For damaged MP4s that still have an index but will not play, see How to repair a corrupted MP4 that won’t play on a Mac.

Making it less likely next time

  • Press stop and wait for the recording light to go out before switching off or removing the card.
  • For long recordings, start with a full battery or mains power, and leave room on the card or the disk.
  • Copy footage to the Mac and check that it plays before deleting anything from the card.

Questions

Does “moov atom not found” mean the video is gone? Not usually. It means the index is gone. If the file is roughly the size you would expect for the length of the recording, the frames are probably in it, and the open question is how much of the index can be reconstructed from them.

Why does QuickTime never say “moov atom”? QuickTime Player uses Apple’s own media framework, which reports the failure in general terms. The specific phrase comes from ffmpeg, which is why you see it in converters, editors and upload pages rather than in Apple’s apps.

Is a MOV file any different from an MP4 here? No. MP4 was built on the QuickTime MOV format and the two share the same atom structure. A MOV from an iPhone or a screen recording loses its index in the same way, and a repair treats it the same way.

Can the missing seconds at the end be recovered? No. They were still in the recorder’s memory when it stopped and never reached the card. A repair returns what the file holds, and nothing beyond it.