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The Sony A7 IV (ILCE-7M4) records into standard MP4 files using one of three XAVC flavours: XAVC S (H.264 Long GOP), XAVC HS (H.265/HEVC), and XAVC S-I (All-Intra H.264), at up to 4K 60p with 10-bit 4:2:2. Every one of those is an MP4 that only becomes playable once the camera writes its moov index at the end of the take. If that final write never happens, you get a file full of real XAVC data and no map to it. Drop the clip above and the tool checks for exactly that, in your browser, and rebuilds the container when the footage is recoverable.
How the A7 IV writes XAVC — and where it breaks
Whatever menu option you pick, the A7 IV wraps its video in an MP4 container. The three formats differ only in the codec inside:
XAVC S is H.264 (AVC) Long-GOP — the most broadly compatible option. XAVC HS is H.265/HEVC, which packs more detail into a smaller file but needs an HEVC-capable player to open. XAVC S-I is All-Intra H.264, where every frame is a full keyframe, at bitrates up to around 600 Mb/s. A quirk worth knowing: XAVC HS on the A7 IV can't record 4K 30p at all — 30p in 4K forces you onto XAVC S — so a lot of shooters end up with a mix of H.264 and H.265 clips on the same card, and a broken one can be either.
In all three cases the actual picture data is streamed to the card as you shoot, but the moov atom — the table that tells a player where every frame lives and how to decode it — is written only when the clip is finalized, at the moment you press stop or the take ends cleanly. Interrupt the recording before that write and the container is left headless: gigabytes of valid H.264 or HEVC, with nothing indexing it. Players respond with "moov atom not found," a codec error, or a stubbornly black frame.
The errors that leave a clip unfinalized
Because the A7 IV has no clip-length limit, a single take can run for an hour of 4K 60p — which also means an interruption near the end can strand a very large file. The usual culprits:
The battery died mid-take. The A7 IV runs demanding formats off an NP-FZ100, and high-bitrate 4K drains it fast. If the pack cuts out during a long clip, the finalization write never runs.
The card was pulled or the door opened. Removing the SD/CFexpress card while the access lamp is still writing does the same thing — the tail of the file, including the index, is simply never committed.
A card write error, often shown as C:13:01. Sony's C:13:01 code is a memory-card fault that frequently appears when the camera is writing large amounts of data — exactly what movie recording is — and can point to a card that can't sustain the write speed or has begun to fail. High-bitrate modes make this worse: XAVC S-I and 4K really want a V60 card, and XAVC S-I high bitrate wants V90; feed the camera a slower card and it can drop or truncate the recording. When the write stalls or the card errors out mid-clip, the last file is left unfinalized.
The interrupted-last-clip cases above are the repairable ones. Where a card physically lost bytes to failing sectors, those bytes can't be invented back — recover the card first, then repair what comes off it.
Why a reference clip from the same body helps
Rebuilding a missing moov means scanning the surviving stream and reconstructing the sample tables the camera would have written. That job is far more faithful when it has a healthy clip from the same A7 IV shot in the same format and settings — same XAVC flavour (S, HS or S-I), same resolution, framerate and bit depth. That reference carries the exact codec configuration (SPS/PPS for H.264, or the equivalent VPS/SPS/PPS for HEVC) that the broken file is missing, so the rebuild matches the original instead of guessing at it.
The practical move: grab any normal clip from the same card or camera, recorded with the same movie settings, and keep it handy. You'll only be asked for it if the broken file actually needs it — and if you switched between XAVC S and XAVC HS, make sure the reference matches the codec of the broken clip, not the other one.
What this can and can't fix
Can fix
- The last clip when the battery died or you stopped power mid-record (unfinalized MP4, missing moov)
- Clips truncated by a card write error or a C:13:01 fault during recording, where the video data survived
- XAVC S (H.264), XAVC HS (H.265/HEVC) and XAVC S-I files that copied off the card but won't play
- Container damage: broken or missing index, wrong sample offsets, bad timestamps
Can't fix
- Footage physically lost to a failing or worn SD/CFexpress card (recover the card first, then repair)
- A clip whose reference you can't match — e.g. no healthy XAVC HS sample for a broken HEVC file
- Files that read as 0 bytes or as mostly zeros after a card failure
- Sony's encrypted/DRM-protected or otherwise locked exports
If a repair fails, we tell you why (missing data versus broken structure), and you are never charged for a failed repair.