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Translate a video file · AI dubbing

MP4 translator: your video file in, a dubbed MP4 out.

DubSync translates a video file by dubbing it. Upload an MP4, MOV or M4V of up to 1 GB and 150 minutes, then choose English or another of the 28 target languages. You get the same video back as an MP4, with the speech in the new language, a voice created from each speaker and your music and background sound kept.

Translate my video intoUpload my video

Pro: 7 days free for eligible new subscribers, with 60 minutes. Card required. Then $29.90/month; cancel before the trial ends to pay nothing. Trial minutes expire after 7 days.

Upload an MP4, MOV or M4V. You see the minutes and the cost before anything starts.

EnglishOriginal

What is said: This is our product demo. We recorded it once, and every customer watches it in their own language.

What is said: Esta es nuestra demostración del producto. La grabamos una vez y cada cliente la ve en su propio idioma.

What is said: Esta é a demonstração do nosso produto. Gravamos uma vez e cada cliente assiste na sua própria língua.

Demo clip: an AI-generated scene with a fictional character. Dubbed with VDub v2, the model DubSync runs; lip-synced tracks use VSync v2.

Lip-sync shown in these examples is an optional paid add-on, separate from the dubbing trial.

MP4, MOV or M4V in
Up to 150 min / 1 GB per file
One dubbed MP4 out
No visible watermark
Pay per input minute

What goes in, what comes out

Three file types go in. One comes out.

DubSync takes a file, not a link: an MP4, a MOV or an M4V. It returns a dubbed MP4, not a subtitle or transcript file. These are the limits for one upload.

Largest file: 1 GB; Size depends on bitrate as well as length.
Longest video: 150 min; Longer than that? Cut it into parts.
Target languages: 28; The spoken language is detected for you.
You get back: MP4; One file per language, with no visible watermark.

Why these three? The extension names the container, the wrapper that holds a video's picture, sound and metadata. MP4 is derived from Apple's QuickTime format, the one behind .mov files, and .m4v is another extension for MP4 video,¹ so the three are close relatives.

Where the file comes from

Most video files are ready as they are. A few need one extra step.

Phone camera
Phone cameras normally save MP4 or MOV, and both are accepted. Use the original from your camera roll, not a copy forwarded through a messenger, which may have been compressed.
Editor export
Choose MP4 in the export dialog. YouTube's recommended upload settings name MP4 as the container,² so the file you export for YouTube is the file to upload here.
Screen recording
macOS saves a screen recording as a .mov file named Screen Recording with the date and time.³ On Windows, Xbox Game Bar saves its recordings as MP4 files in the Captures folder under Videos.⁴ Both are accepted, as long as the recording has sound.
OBS and other recorders
OBS Studio 32.0 made Hybrid MP4 and MOV the default for new profiles.⁵ Its 2023 recording guide recommends MKV, which isn't ruined when a recording stops without warning.⁶ Check which one you have: an MKV has to become an MP4 first.
A video already on YouTube
Lost the original? YouTube Studio lets you download your own upload as an MP4, in 720p or 360p depending on the video.⁷ That file works, but your own export is the better source.
Recorded calls and webinars
Check the extension: an MP4 uploads as it is. Everyone who speaks in the recording has to agree to their voice being dubbed, guests included.

MKV, WebM, AVI and the rest

A different format? Turn it into an MP4 first.

DubSync doesn't convert files. Your video editor can, and so can free tools.

Files DubSync doesn't accept, and what to do with each
	What it is	What to do
MKV	Matroska, an open container format.⁸	If it came from OBS, open File, choose Remux Recordings, pick the file and click Remux to get an MP4.⁶ Otherwise use an editor or a converter.
WebM	A format designed for the web and based on Matroska.¹	Convert it to MP4 in an editor or a converter.
AVI	An early Windows video format, introduced by Microsoft with Windows 3.1.⁹	Convert it the same way.
MP3, WAV, M4A	Sound without a picture.	Not accepted. DubSync dubs video files only.
A link	An address, not a file.	Not accepted. Upload the original file of a video you own or have licensed.

Remux: same video, new wrapper
- No quality loss
- Doesn't work for every file
A remux copies the existing video and audio into a new container. FFmpeg's documentation calls it streamcopy: nothing is decoded or encoded, so it is fast and loses no quality, but it can fail when the new container needs information the old file lacks.¹⁰
Convert: decode and encode again
- Works for most common files
- Use a high quality setting
A converter decodes the video and writes a new one. HandBrake, a free open-source transcoder for Linux, Mac and Windows, turns most common video files into MP4 and always converts the video.¹¹ A new encode usually costs a little detail, so convert once, from the best copy you have.

YouTube accepts AVI, WMV, FLV and WebM uploads,¹² so a file that went onto YouTube without trouble can still need converting here.

Check before you upload

A file that is ready, and a file to fix first.

Ready to upload

The name ends in .mp4, .mov or .m4v, and the file really is one.
It is 1 GB or smaller and 150 minutes or shorter.
It has sound: speech, music and effects in one mix, as viewers hear it.
It is the finished cut, with nothing left to trim.
It is your video, or licensed to you, and everyone who speaks in it agreed.

Fix it first

MKV, WebM, AVI or anything else: remux or convert it to MP4.
Larger than 1 GB: export it again at a lower bitrate or resolution, but only as far as you would still publish. The dub is made from this file.
Longer than 150 minutes: cut it into parts at a natural pause. Each part is its own project.
No audio track, such as a silent screen capture: there is no speech to translate, and the file is rejected.
Long intros, dead air and outtakes: trim them. You pay per input minute for the whole file.

Into English

Translate an MP4 to English.

A Spanish file in, an English file out

The file is in Spanish, Portuguese or another language, and you need it in English. You only choose the target: the language spoken in the file is detected for you.

This demo scene was made in Spanish. Play it, then switch the language under it. Tracks the player marks as lip-synced, here and in the clip at the top of the page, also have the optional paid lip-sync add-on applied. A standard dub leaves the picture as it is.

The other direction works the same way: an English file can be dubbed into any of the other 27 target languages.
One language per project. A second language is a second project and uses the file's minutes again.
A dub changes the sound only. Titles, slides and burned-in captions stay as they are.
More on this case: dub a video into English, or see all languages.

SpanishOriginal

What is said: Mis clientes me envían su video. Yo les entrego la versión en inglés revisada y lista para publicar.

What is said: My clients send me their video. I deliver the revised English version ready for publishing.

What is said: Meus clientes me enviam seu vídeo. Eu entrego a versão em inglês revisada e pronta pra publicação.

Demo clip: an AI-generated scene with a fictional character. Dubbed with VDub v2, the model DubSync runs; lip-synced tracks use VSync v2.

Lip-sync shown in these examples is an optional paid add-on, separate from the dubbing trial.

Upload. Translate. Download.

How to translate a video file in four steps.

Upload your original.
MP4, MOV or M4V, up to 1 GB and 150 minutes. We detect the spoken language for you.
Choose English or any of 28 languages.
We calculate the input minutes your video needs before you pay anything.
Review and confirm.
See the minutes and the cost, confirm your rights and every speaker's voice consent, then start the dub.
Download your MP4.
A voice for each speaker, your background audio kept and no visible watermark. Add lip-sync if you need it, priced per minute.

After the download

What you get back, and what you don't.

An ordinary MP4
The dub is a normal video file with no visible watermark, in the container YouTube recommends for uploads.² Watch it through before you post it. Where you post it is up to you.
One language per file
Each MP4 carries the dubbed speech in one language over your original music and background sound. For a YouTube audio track, YouTube asks for an audio-only file about as long as the video,¹³ so export the sound from the MP4 in an editor first. The multi-language audio guide has the steps.

Whose file is it

Having the file is not the same as having the rights.

A film, a series episode or someone else's video saved as an MP4 still belongs to its owner, and so do the voices in it. DubSync is for files you made or have licensed. If you only want to watch something in another language, look for an official dubbed or subtitled release. If the film is yours, see the movie translator page.

Questions

Questions before you start

How do I translate an MP4 file to English?

Upload the MP4, choose English as the target language and confirm the quote. The language spoken in the file is detected for you. You get the same video back as an MP4 with the speech in English, a voice created from each speaker (similar, not identical) and your background audio kept. It is a dub, so there is no subtitle file.

Which video formats can I upload?

MP4, MOV and M4V, up to 1 GB and 150 minutes per file. MKV, WebM, AVI and other formats have to be converted to MP4 first. Audio-only files and links are not accepted.

Does converting to MP4 lower the quality?

A remux doesn't: it copies the existing video and audio into the new container without encoding them again.¹⁰ A converter that encodes the video again usually costs a little detail, so pick a high quality setting. Renaming the file converts nothing, and a renamed file is rejected.

My file is over 1 GB or 150 minutes. What can I do?

For size, export it again at a lower bitrate or resolution. For length, cut it into parts at a natural pause and dub each part as its own project. You pay for the length of what you upload, so the parts add up to the same minutes as the whole.

Is this MP4 translator free?

No. DubSync is paid per input minute: the length of your original video, for each target language. You upload first and see the minutes and the cost, and the dub starts only after you confirm. Converting a file to MP4 beforehand costs nothing if you use a free tool.

What happens to my files?

Source files are scheduled for deletion after 7 days and exported videos after 30 days, so download your dubbed MP4 when it is ready and keep your own copy of the original.

Plans from $4.90/month. You see the minutes and the cost before anything starts. See pricing

Sources

MDN Web Docs. Media container formats (file types). Accessed Oct 5, 2026.
YouTube Help. YouTube recommended upload encoding settings (help article 1722171). Accessed Oct 5, 2026.
Apple Support. How to record the screen on Mac. Published Sep 14, 2026; accessed Oct 5, 2026.
Microsoft Support. Use a screen reader to record your screen with Xbox Game Bar. Accessed Oct 5, 2026.
OBS Project on GitHub. OBS Studio 32.0.0 (release notes). Published Sep 22, 2025; accessed Oct 5, 2026.
OBS Project. Standard Recording Output Guide. Published May 26, 2023; accessed Oct 5, 2026.
YouTube Help. Download YouTube videos that you've uploaded (help article 56100). Accessed Oct 5, 2026.
Library of Congress. Matroska Multimedia Container. Accessed Oct 5, 2026.
Library of Congress. AVI (Audio Video Interleaved) File Format. Accessed Oct 5, 2026.
FFmpeg. ffmpeg Documentation. Accessed Oct 5, 2026.
HandBrake Documentation. About HandBrake. Accessed Oct 5, 2026.
YouTube Help. Supported YouTube file formats. Accessed Oct 5, 2026.
YouTube Help. Add Multi-language features to your videos (help article 13338784). Accessed Oct 5, 2026.

Start with one file

Got the file? See the minutes and the cost first.

Upload it, read the quote, then decide.

Upload my video

Only upload videos you have the rights to, with every speaker's permission.