FX30 RSV file repair: getting an interrupted take back

Updated 3 November 2026

The FX30 often works as the second camera: the wide shot left running on a tripod, the B-cam at an interview, the camera nobody watches. That is exactly the one whose battery dies unnoticed. When you get to the card, the take is a .RSV file instead of an .MP4.

Below: how to tell what kind of problem you have, what to avoid, what to try for free, and how the repair itself works.

First, which problem do you have?

"Repair" and "recovery" get mixed up, and the fix depends on which one you need:

What you see on the card	What it means	What to do
A `.RSV` file of a few GB in `PRIVATE/M4ROOT/CLIP`	The recording was interrupted before the camera finished the file. The footage is there; the index is missing.	Copy the card, try the camera, then rebuild the index (this guide).
A `.RSV` of 0 KB or a few KB	The camera stopped before it wrote real data.	Nothing to rebuild. Check the other card slot.
No file at all, or the card was formatted	The file was deleted or the card was wiped.	Stop using the card and use data recovery software first. If it brings back an `.RSV`, come back to this guide.
An `.MP4` that plays badly or stutters	Usually a playback or decoding issue, not a broken file.	Try another player or an editor that supports the format.

If you are in the first row, read on. If you want the background first, see What is an RSV file?

Keep the card exactly as it is

Don't format it and don't let the camera "fix" the card by formatting it.
Don't record on it again: swap in a different card for the rest of the shoot.
Don't delete the .RSV or move it around on the card itself.
As soon as you can, copy the whole PRIVATE folder to your computer with a card reader. Your clips are in PRIVATE/M4ROOT/CLIP, named C0001, C0002 and so on; the interrupted take usually carries the number it would have had as an .MP4.

Free things to try

Let the camera have a go

Some Sony cameras try to recover an interrupted clip on their own when you put the card back into the same camera with a charged battery. It doesn't work in every case and we can't say in advance whether your FX30 will do it, but it costs nothing once your copy is safe. Use the same camera and the same slot, switch on, and if a message about recovering data appears, let it finish.

Look at the other card

The FX30 has two card slots. If it was set to record to both at once and only one card came out, the other card may already hold a complete .MP4. If the battery died, both cards will normally have an .RSV; keep both, they are two copies of the same take.

Repairing the FX30 file

The FX30 records XAVC S, XAVC S-I (H.264) and XAVC HS (H.265) into .MP4 files. The repair is the same for all three: go through the recorded data, find each video frame and each block of audio, and write the index the camera didn't get to write. Nothing is re-encoded.

Lazaclip is our Windows 10/11 program for this (we make it, so read this part as coming from the seller):

Open the card or the folder you copied. The program lists every .RSV it finds and checks each one.
Watch the free Preview 10 s: the start of the take, watermarked, in your own video player.
With a license, save the full .MP4, or use Repair all if several takes or both cards are affected. One license covers all your files on one computer.

Everything runs on your PC; nothing is uploaded, and the .RSV is opened read-only. Save the result to your computer's drive, not to the card, with free space of about the size of the .RSV.

Has it been tested on the FX30?

Not yet, and we'd rather say so. We tested Lazaclip on A7S III recordings in XAVC S 8-bit and 10-bit, XAVC S-I and XAVC HS, all rebuilt without a reference clip and with frames and audio identical to the original up to the last unfinished group of frames. The FX30 uses the same XAVC S / XAVC HS recording format; the free preview shows whether the program can read your file before you pay.

What the repair can't do

The last second or so before the cut is not recoverable: that group of frames was never finished.
If you recorded more on the card after the interruption, part of the .RSV may have been overwritten.
Slow and quick motion and other modes we haven't tried may not rebuild; the free preview shows whether the program can read your file.

Keeping the B-cam from doing it again

A camera nobody is watching needs the most battery margin. Start every long take on a full battery.
For locked-off cameras at long events, consider external power; check the FX30 manual for the power options it supports while recording.
Recording to both slots at once gives you a backup of every take.
Stop recording before touching the card door, and wait until the camera has finished writing.

Running an FX3 next to it? See the FX3 guide. If your A-cam is an A7S III, see the A7S III guide.