Replace the audio in a video
Drop in a video and the new sound, and get the video back with that sound on it. Nothing is uploaded: the picture is copied as it is and only the sound is written, in this tab.
- A new soundtrack on an MP4, MOV or WebM
- The picture is copied, not re-encoded
- Remove the old sound or keep it quietly
- Runs in this tab, nothing uploaded
- Video
- -
- New sound
- -
- You get
- -
This browser cannot read the length of a file before writing, so there is no comparison of lengths. The video is still written in full.
Nothing is uploaded. Close the tab and the files are gone.
What happens to the video
The picture is not touched. The video stream is copied from the old file into the new one as it is, frame for frame, so there is no loss of quality and the job takes seconds rather than the minutes a re-encode would. Only the sound is encoded, as AAC at 160 kbps, the audio format every player and platform takes in an MP4.
Where the new sound comes from is up to you: a narration you recorded, music, or a voice-over made from the video itself. In Speecho a video is transcribed, translated if you like, and voiced on its own timing, each speaker in a voice of their own; the track that comes out is as long as the video and starts where it starts, so it goes on here with nothing to line up.
Questions
Not covered here? Ask us, we usually reply within a business day.
Are my files uploaded anywhere?
No. The engine (ffmpeg, compiled for the browser) is downloaded to your tab the first time, and after that everything happens on your device. Your browser's network tab shows that neither file is sent.
Does the picture lose quality?
No. The video stream is copied, not re-encoded, so the picture in the new file is bit for bit the one in the old. Only the sound is encoded.
What if the sound is shorter or longer than the video?
A shorter sound is followed by silence to the end of the video (or by the original sound, if you keep it underneath). A longer one is cut where the video ends. The page says which it is before you start.
Can I keep the music and sound effects?
Choose to keep the original sound quietly underneath, at a level you set. The original speech stays in it too: a mixed track cannot be taken apart here. For a clean result, use a version of the music without speech, or remove the original and add the music again in an editor.
Will the new voice match the speaker's lips?
No. The sound starts at the beginning of the video and keeps the timing it was made with; nothing moves it to the picture. A voice-over made from the video's own transcript lands on the right seconds, but the lips are not changed.
Which formats come out?
MP4, MOV and M4V give an MP4; WebM gives a WebM; MKV and the rest give an MKV. The new sound can be an MP3, WAV, M4A, AAC, OGG or FLAC.
How big a video can it take?
The whole output is held in the tab's memory, so about 1 GB on a computer and 300 MB on a phone. For a bigger file, use a desktop editor, or ffmpeg on the command line: it is the same job.