Repair a corrupted Sony A7 IV video

Whatever you pick in the menu, the A7 IV wraps its video in an MP4 container; the three XAVC 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. One A7 IV quirk worth knowing: XAVC HS can't record 4K 30p at all — 30p in 4K forces you onto XAVC S — so a hybrid shooter who changes modes between jobs often ends up with a mix of H.264 and H.265 clips on the same card, and a broken one can be either.

Whatever picture profile you chose — S-Cinetone for a graded-in-camera look, or S-Log3 to grade later — is encoded into that H.264 or HEVC stream itself, not into the container around it. That matters here: rebuilding the moov only rewrites the map to the frames, never the frames, so your S-Cinetone colour comes back exactly as shot. And that map is the fragile part — the moov atom that tells a player where each 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 them, and players answer with "moov atom not found," a codec error, or a stubbornly black frame.

Because the A7 IV is a hybrid, most people shoot it in short, run-and-gun takes between stills — so the clip that breaks is usually a recent one caught mid-write, not a marathon recording. The usual culprits:

A Relay Rec hand-off between the two slots. The A7 IV has dual card slots — slot 1 takes CFexpress Type A or SD UHS-II, slot 2 takes SD UHS-II — and with Relay Rec on it rolls from a full card onto the second one mid-take, splitting a long clip across files. Lose power or lose a card during that hand-off and the clip being written is left without its finalizing pass.

The card was pulled, or the door opened, mid-write. On a hybrid you're swapping cards constantly to offload stills, and yanking the SD or CFexpress Type A card while the access lamp is still lit does it every time — the tail of the file, index included, is simply never committed.

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 clip, the finalization write never runs.

A card write error, often shown as C:13:01. Sony's C:13:01 is a memory-card fault that turns up when the camera is writing hard — exactly what 4K and XAVC S-I do. Those modes want a fast card (XAVC S-I and 4K really want a V60, high-bitrate S-I wants V90, and the top modes lean on CFexpress Type A); feed the camera a slower card and it can stall and truncate the clip.

A thermal stop on a long take. The A7 IV is fanless, so a sustained 4K 60p take can hit its thermal limit and end on its own; when a take ends that way rather than on a clean stop, the finalizing write can be skipped. On a hybrid used for short clips this is the exception rather than the rule — and it's the one failure the fan-cooled FX3 rarely lands, worth remembering if you also shoot that body.

All of these strand the last clip mid-write, and all of them are the repairable case. 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.

Rebuilding a missing moov means scanning the surviving stream and reconstructing the sample tables the camera would have written on stop. That reconstruction is far more faithful with 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, frame rate and bit depth. The reference carries the exact codec configuration the broken file lost — SPS/PPS for H.264, or VPS/SPS/PPS for HEVC — so the rebuild matches the original instead of guessing at it.

Because you're usually offloading a hybrid card full of both stills and video, a matching clip is normally right there: grab any normal take 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 between takes, make sure the reference matches the codec of the broken clip, not the other one.