MP4 to AC3 Converter

What happens when you convert MP4 to AC3

• AC3 holds sound only, so the picture is discarded and the soundtrack is encoded as Dolby Digital at 192 kbps.
• If the MP4 has several audio tracks, the first one is used.
• Surround soundtracks keep up to six channels in the AC3; stereo stays stereo.

How to convert MP4 to AC3 online

1. Press "Choose MP4 files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
2. Adjust the settings if you need to: the bitrate controls quality and size. The defaults suit most people.
3. Press "Convert to AC3". The first audio or video conversion downloads the converter engine, about 32 MB, which your browser then keeps for next time.
4. Save each AC3 with its download button. Close the tab and every trace of the files is gone from memory.

Why convert MP4 to AC3?

MP4 files usually come from phone videos, YouTube uploads, social media and streaming. People convert them to AC3 because AC3 (Dolby Digital) is the audio format DVD authoring and many AV receivers expect.

In short, MP4 is good at what it was made for, and AC3 is the more practical choice when the file has to play on another device or app. MP4 plays in every browser, phone and smart TV, while most browsers do not play AC3; Safari on Apple devices does.

How to convert MP4 to AC3 on Windows, Mac, iPhone and Android

On Windows

Open this page in Chrome, Edge or Firefox, drag your MP4 files in from File Explorer, and press Convert. Each AC3 is saved to your Downloads folder. If you prefer a desktop program, VLC can also convert MP4 to AC3: choose Media, then Convert / Save.

On a Mac

Safari, Chrome and Firefox all work. Drag the MP4 files from Finder onto the drop zone and the AC3 files land in Downloads.

On iPhone and iPad

Open the page in Safari and tap Choose MP4 files. You can pick from Photos or from the Files app. The converted AC3 appears in Files, in the Downloads folder.

On Android

Open the page in Chrome, tap Choose MP4 files and pick them from Files or your gallery. The AC3 is saved to the Download folder, where any file manager can find it. Keep the screen on while a long video converts, because Android may pause a tab in the background.

Best settings for MP4 to AC3

AC3 is a lossy format, so the bitrate decides both the sound quality and the file size. Size grows in a straight line with bitrate: double the bitrate and the file doubles.

The MP4 was already compressed, so pick a bitrate at least as high as the original. Going higher does not add quality back, it only makes the file bigger.

MP4 vs AC3: the differences

About MP4 and AC3 files

What is an MP4 file?

MP4 is the most widely supported video format, and H.264 video with AAC audio inside it plays on essentially every device made in the last fifteen years.

What is an AC3 file?

AC3 carries surround sound for DVDs and broadcast TV, up to six channels. Converting it to a stereo format mixes those channels down.

MP4 to AC3 not working? Common problems

• The conversion is slow. Audio and container changes take seconds, but re-encoding video runs on your own processor. Lower the resolution to 720p, close other tabs, and keep the device plugged in.
• The tab stops or reloads on a very large file. Browsers limit how much memory one tab can use, around 2 GB and less on phones. Split long recordings or convert them on a computer.
• Song titles are missing. Tags such as title and artist are copied when AC3 can store them, but cover art is not carried over.

Convert MP4 to AC3 with ffmpeg

This converter runs ffmpeg inside your browser. If you would rather use the ffmpeg command line on your own computer, this command produces an equivalent AC3 with the same kind of settings:

ffmpeg -i input.mp4 -vn -c:a ac3 -b:a 192k output.ac3

Replace input.mp4 with the name of your file. For a whole folder of MP4 files, run the command in a loop, or drop them all on the converter above, which processes them one after another.