Lazaclip

RSV repair failed? The reference file, explained

Updated 8 November 2026

You found a free way to turn a Sony .RSV file back into an .MP4, followed the steps, and it stopped with an error, or it produced a file with no picture, broken blocks or sound that drifts away from the image. A common reason is the reference file. This guide explains what that file is for, what has to match, and what you can do if you don't have a matching one.

First: keep the original safe

Every failed attempt is harmless as long as you work on a copy. Before you try anything else:

  • Don't format the card, even if the camera or the computer suggests it.
  • Don't record on that card until the take is back. New recordings can land on the space the interrupted take occupies.
  • Don't delete the .RSV, and don't let a repair tool save its output onto the card.
  • Copy the whole PRIVATE folder to a drive on your computer. The recordings are in PRIVATE/M4ROOT/CLIP, next to your healthy .MP4 clips, which you will need below.

Why some repair methods need a reference file

An .RSV is a recording the camera never finished: the picture and sound are in the file, but the index that tells a player where each frame and each piece of audio sits was never written. Background: What is an RSV file?

To write that index again, a repair method has to know how the recording was encoded: the codec and its settings, the frame rate, how the audio is stored. Many methods learn this from a second, healthy file. They read its index, assume the broken recording was made the same way, and use it as a pattern. That healthy file is the reference.

This works well when the reference really matches. When it doesn't, the repair may stop with an error, or build an index that points to the wrong places: the file opens, but the picture is choppy or broken, or the sound is out of step with the picture.

What has to match

The reference should come from the same camera, recorded with the same settings as the broken take. The settings that matter most:

  • Codec: XAVC S (H.264) and XAVC HS (H.265) are different, and so is the All-Intra XAVC S-I.
  • Resolution and frame rate: a 4K 25p clip is no pattern for a 4K 50p or an HD take.
  • Bit depth and colour sampling: 8-bit 4:2:0 and 10-bit 4:2:2 are recorded differently.
  • Bitrate: the same mode can have more than one bitrate option.
  • Audio: the same audio format and number of channels.

How to find a matching reference

  1. Look in the copied PRIVATE/M4ROOT/CLIP folder for a healthy .MP4 recorded just before the cut. On a shoot you rarely change settings between takes, so the clip right before is the best candidate.
  2. Compare the two. A free media information tool shows the codec, resolution, frame rate, bit depth, colour sampling and bitrate of the healthy clip; the camera's own menu tells you what is set now, which is what the broken take used if you haven't changed anything since.
  3. If no clip on the card matches, set the camera exactly as it was and record a few seconds on a different card. Never on the card that holds the .RSV.
  4. Run the repair on the copy, never on the card, and save the result to your computer.

The free try that needs no reference at all

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 happen with every model or every interruption, but it costs nothing, and because you already have a copy, you lose nothing by trying. If a message about recovering or repairing data appears, let it finish without switching off, then check the folder for a new .MP4.

If the camera was recording to both card slots and only one card was pulled out, the other card may hold a finished .MP4 of the same take. After a dead battery, both cards usually hold an .RSV: keep both and copy both.

Rebuilding without a reference file

Newer cameras, such as the A7S III we tested, store the codec settings inside the recording itself, so no second file is needed to decode the video. Lazaclip is our Windows 10/11 program that reads them from there (we make it, so take this section as coming from the seller). It works offline and never changes the original:

  1. Open the card or the folder you copied. The program lists every .RSV it finds and checks whether each one can be rebuilt.
  2. Click Preview 10 s to watch the first ten seconds of your recording with a watermark. The scan and the preview are free.
  3. With a license, save the full .MP4 to a folder on your PC, or repair every .RSV on the card in one go.

Older cameras, such as the original a7S from 2014, don't store these settings. For those the program still needs a reference: it looks for a healthy clip in the same mode on the card or in the folder you open (a test clip recorded on another card can be copied into that folder) and checks it against the damaged file first. If none matches, it says so instead of making a broken file.

What has been tested

Our tests use A7S III recordings (XAVC S, XAVC S-I and XAVC HS, rebuilt without a reference clip, with frames and audio identical to the original up to the last unfinished group of frames) and the original a7S with a reference clip. Cameras such as the FX3, FX30, A7 IV and ZV-E1 use the same XAVC S / XAVC HS recording format, but we haven't tested files from them yet; the free preview shows whether the program can read your file before you pay. Model guides: A7S III, FX3, ZV-E1.

What a rebuild can't bring back

  • The last second or so before the cut. That final group of frames was never completely written.
  • Parts of the file that were overwritten because the card was used again.
  • A file that was deleted, or a card that was formatted: that needs data recovery first, the rebuild comes after.