My FLV shows the wrong length. Did it record properly?

The footage is almost certainly complete. FLV writes its duration into a metadata block at the start of the file, before the length is known, and a crash leaves that placeholder in place. Remuxing recalculates it from the tags.

Should I still record FLV in OBS?

No. It survives crashes well, but so does fragmented MP4, which every editor opens.

Flash Video .flv · recording recovery

A crash during an FLV recording costs you one tag

The tag being written — a fraction of a second. FLV timestamps every tag, so everything before the cut stays readable.

A crash costs you

One tag

Index is written

Continuously

Editable directly

Not without a remux

Drop the recording that will not open

Any Flash Video .flv file, however large.

Nothing is uploaded

The check runs entirely in this tab. Your browser reads a few hundred kilobytes of headers from the start and end of the file and never sends any of it anywhere — you can watch the network tab, or turn off your Wi-Fi and run it again.

What you will get back

Which container OBS actually wrote, and whether it writes its index as it goes or only at the end.
How many hours and minutes of footage are still readable, measured from the timestamps inside your file — not estimated from its size.
The exact command that turns it back into a file you can play, and what that command will and will not recover.

Why Flash Video behaves this way

FLV was built to be streamed to a Flash player, so like MKV and TS it is readable before it is finished. It survives a crash comfortably. Its problem is age, not fragility — modern editors have been dropping support for years.

How to get a playable file back

ffmpeg -i broken.flv -c copy fixed.mp4

A remux moves the frames into MP4 and writes an honest duration in place of the placeholder the crash left behind.

Editing .flv

Poor. Treat FLV as an intermediate to be remuxed immediately, never as something to cut.

Flash Video questions

My FLV shows the wrong length. Did it record properly?: The footage is almost certainly complete. FLV writes its duration into a metadata block at the start of the file, before the length is known, and a crash leaves that placeholder in place. Remuxing recalculates it from the tags.
Should I still record FLV in OBS?: No. It survives crashes well, but so does fragmented MP4, which every editor opens.

Stop needing this page

The container decides how much you lose. A second copy decides whether it matters.

WeaverClip records fragmented segments and uploads each one while you are still live, verifying byte count and MD5 before anything leaves your disk. Free holds 10 GB for 30 days without a card.

Start free — no card How the vault works