Fix a Corrupted MOV from a Sony A7S III

The Sony A7S III — alongside its newer siblings the Sony A1 II (Nov 2024), A9 III (early 2024), and the recently introduced FX2 (May 2025, slotting between FX30 and FX3) — records to MOV containers using XAVC HS (H.265) or XAVC S (H.264). Both are robust, modern codecs. The container — the metadata wrapper that tells your editor where each frame lives in the file — is the part that fails. When you see "the file is damaged" in DaVinci Resolve, "the document could not be opened" in QuickTime, or a confused error message in Premiere, the codec data is almost always still intact. The map to the data is what's missing.

This page explains what fails specifically on the A7S III, what you can try yourself, and when an automated rebuild service is faster than fighting the file by hand.

What actually broke in your A7S III file

The MOOV atom is the index. It tells your player every frame's position, size, codec parameters, timecode, and duration. The A7S III writes the MOOV atom at the end of the recording, not during it. If the camera doesn't reach a clean stop, the MOOV is never written, and the file ends with raw video data and no map.

Common A7S III triggers for this exact failure:

• Battery exhaustion mid-record — the most frequent. The camera shuts off rather than gracefully stopping the file.
• Hot shutdown — the A7S III is famously thermal-tolerant compared to siblings, but extended 4K 120p sessions in heat still trip the cutoff. The file mid-record is left without a MOOV.
• CFexpress Type A card pulled before stop — common during rushed memory-card swaps.
• Card error / write fault — the A7S III is generally fine, but lower-quality CFexpress Type A cards with thermal throttling have produced this in the wild.
• Power lost from a dummy battery during studio shooting.

The recording on the card looks like this:

[ftyp] ── small atom that says "this is an MP4/MOV" ── intact
[mdat] ── all of your H.265 (or H.264) frames + audio ── intact
[????] ── where MOOV should be ── empty / cut off

The frames are sitting in mdat. Nothing actually decoded the data and discarded it. We just need to rebuild the index.

What you can try yourself first

Before paying anyone — including us — try these in order:

1. Sony's own Catalyst Browse / Catalyst Prepare. Sony's free tool understands its own XAVC variants better than third-party software. If the file's only issue is metadata-related, Catalyst sometimes opens it directly.
2. untrunc (open source, GitHub). Specifically built for truncated MP4/MOV. Needs a "good" reference file from the same camera in the same recording mode. If you have a healthy A7S III file at the same resolution, fps, and codec, untrunc has a real chance.
3. ffmpeg -i broken.mov -c copy out.mov. Doesn't fix anything but tells you what FFmpeg sees. If FFmpeg returns useful information about streams, the file is salvageable.
4. mediainfo broken.mov. Second opinion on what's intact.

If those fail or you don't have a matched reference clip, the manual path is hours of trial-and-error on atom layout, codec parameters, and audio stream detection. You can either learn it (real engineering work) or hand it off.

How our recovery works on A7S III files specifically

Our engine handles the A7S III well because the hard parts are the parts we focused on:

• No reference clip required. We rebuild the index from the frames themselves. The H.265 / H.264 sequence parameter set is recovered from the first valid IDR frame in mdat — that gives us resolution, profile, level, chroma format, and frame rate.
• XAVC HS vs XAVC S detection. A7S III files carry either depending on the menu setting. Our codec detector handles both; we don't assume the file is one or the other based on file extension.
• Proper co64 for files over 4 GB. Long A7S III takes routinely cross 4 GB. The 32-bit chunk offset table (stco) overflows silently past that point — many cheap tools produce a file that plays the first 8 minutes correctly and then renders colour noise. We use co64 (64-bit) by default for any file ≥ 4 GB.
• Audio probing. A7S III audio is LPCM 24-bit 48 kHz, two-channel, big-endian within MOV. Some recoveries get audio working but at the wrong sample rate or with channels swapped — we check the data distribution rather than trusting the (potentially missing) header.

What you do

1. Upload the broken MOV — drag and drop, up to 50 GB.
2. About a minute later you get a free 5-second preview of the recovered video. You can scrub through it. If the picture is right and the audio is right, you know the rest of the file will be too.
3. If the preview looks correct, pay $5 / $15 / $29 (depending on size) and download the full recovered file.
4. If the preview is wrong, tweak parameters interactively (frame rate guess, audio swap, codec hint) and regenerate. No charge.

If automated recovery doesn't nail it on the first generation, you can escalate to manual review — a human looks at the file. Still no payment until you have a working file.

FAQ

Does this work on the A1 II, A9 III, A7 IV, A7C R, the FX2/FX3/FX30 lineup, and BURANO? Yes. All current Sony Alpha and Cinema-line bodies write the same XAVC family with the same MOOV-finalisation behaviour. Same recovery path. The codec varies (H.264 vs H.265, All-Intra vs Long GOP) and our detector handles all of them. BURANO's X-OCN 16:9 mode (added in the March 2025 firmware) is supported structurally — the wrapper is XAVC-family even though the codec is X-OCN.

Will this work on XAVC HS (H.265) and XAVC S (H.264)? Yes, both. The codec is identified from the frame data, not the file extension. The A7S III's All-Intra and Long GOP modes are both handled.

My file is from a 4K 120p recording — does that matter? No. Frame rate is detected from the codec parameters or, if those are missing, from the timestamps embedded in the frames themselves. The recovery handles up to 240 fps natively.

Can you recover S-Log3 / S-Cinetone tonal information? We rebuild the container, not the colour pipeline. If your camera was set to S-Log3 and the codec data carries that gamma, the recovered file will too. Colour metadata (matrix, transfer function) is inferred from the SPS where present.

The A7S III shoots dual codec / proxy. Does that help? Sometimes a lot. If the proxy file is intact but the main file is broken, the proxy gives us a known-good reference for resolution, fps, and timing. Upload both — we can use the proxy as a hint.

Is my footage safe? File goes to a server in France, gets auto-deleted after 48 hours, never used to train anything or shared. Privacy policy.

Related

• What "MOOV atom not found" actually means
• Sony FX3 XAVC corrupted file (related codec / similar failure mode)
• How our recovery engine works

Upload your A7S III file →