Question 1

What files can I drop?

Accepted Answer

A raw H.264 stream with a .h264, .264, or .avc name.

Question 2

Does this re-encode the video?

Accepted Answer

No. FFmpeg uses -c:v copy. It only packages the stream into MP4.

Question 3

Does the file leave my device?

Accepted Answer

The remux runs in the tab. FFmpeg WASM must load from unpkg first.

Question 4

What is faststart?

Accepted Answer

The MP4 is written so players can begin before the whole file is read.

Question 5

Why is playback at 30 fps?

Accepted Answer

A raw stream often has no timing. This page assumes 30 fps when that happens.

Question 6

Can a huge file fail?

Accepted Answer

Yes. Browser memory can run out. Keep the original dump.

Question 7

Will quality change?

Accepted Answer

No. Copy remux does not change the pictures.

Question 8

Can I add audio here?

Accepted Answer

No. This only wraps the raw video stream.

Question 9

Is this a movie download site?

Accepted Answer

No. You bring your own stream.

Question 10

Should I use Convert Video instead?

Accepted Answer

Yes, if the source is already a packaged clip and you need another format.

Question 11

Does this work offline after load?

Accepted Answer

After the WASM build is cached, the remux can stay in the tab. First load needs unpkg.

H.264 to MP4 - Remux a Raw Stream, No Re-encode