MPEG-2 to AC3 Converter

Extract the Soundtrack from an MPEG-2 File as AC-3

An .mpeg2 file is an MPEG program stream: a video track and, usually, an audio track multiplexed together. This tool pulls the audio out and re-encodes it as AC-3 (Dolby Digital), the audio codec the DVD-Video and ATSC specifications were built around and the one that carries 5.1 surround in a single elementary stream. The video is discarded. Everything below — the bitrate the presets actually produce, what happens to a 5.1 mix, and what happens when the source has no audio at all — was checked against the encoder rather than assumed.

How to Convert MPEG-2 to AC-3

1. Upload Your MPEG-2 File: Drag the .mpeg2 onto the page or click "+ Add Files"; several files can be queued and share the same settings. They are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.
2. Choose a File Compression mode: "Quality Preset" is the mode the page opens in and runs from Highest down to Lowest. "Constant Bitrate" gives you a fixed list from 32 kbps to 384 kbps, and "Custom Bitrate" takes a typed figure in bps, kbps or Mbps.
3. Set Audio Channel and Audio Sample Rate (Optional): Audio Channel offers Original, Mono and Stereo — leave it on Original to keep a 5.1 mix intact. Audio Sample Rate offers Original plus fixed values; AC-3 only supports 32 kHz, 44.1 kHz and 48 kHz, and anything lower you pick is snapped up to the nearest one it can use.
4. Trim and Convert: The Trim group takes a start time and a duration, in seconds or as HH:MM:SS.sss, if you only need part of the soundtrack. Click Convert to download the .ac3.

What Each Quality Preset Produces

AC-3 has no variable-bitrate mode, so the quality preset resolves to a constant bitrate. The figure is calculated from the preset, the channel count and the sample rate, and the encoder then snaps it to the nearest rate the AC-3 frame table allows. For a two-channel 48 kHz source — the usual case for a DVD-era MPEG-2 file — we measured the encoder landing on these:

Two things follow from that table. The dropdown opens on Highest, so leaving it alone gives you 640 kbps — the maximum AC-3 allows and considerably more than a commercial DVD ever used. And because the calculation scales with channel count, a 5.1 source pushes every preset except the lowest against the same 640 kbps ceiling. If you want the rates a real disc uses — 192 or 224 kbps stereo, 384 or 448 kbps for 5.1 — switch to Constant Bitrate and pick them directly.

AC-3 Constraints Worth Knowing

Frequently Asked Questions

What happens if my MPEG-2 file has no audio track?

The conversion fails rather than returning a silent AC-3. We tested this directly: encoding a video-only MPEG-2 program stream to .ac3 ends with "Output file does not contain any stream" and no file is written. This catches people out most often with MPEG-2 files produced from still images, which are silent by construction — if you made the file yourself from photographs, there is nothing in it to extract.

Will my 5.1 mix survive, or does it get folded to stereo?

It survives, as long as Audio Channel is left on Original. AC-3 handles up to six channels and we confirmed a 5.1 program stream coming back out as 5.1 with the side layout intact. Choosing Mono or Stereo explicitly downmixes; there is no reason to do that unless the destination device cannot handle surround.

Why can't I pick 8000 Hz even though it is in the dropdown?

You can pick it, but AC-3 cannot encode it. The sample-rate list is shared across audio targets, and any value AC-3 does not support is snapped to the nearest one it does — the codec's legal set is 32 kHz, 44.1 kHz and 48 kHz. The job does not fail; the output simply arrives at 32 kHz. Leave the setting on Original unless you have a specific reason, since almost every MPEG-2 soundtrack is already 48 kHz.

Is the audio re-encoded or copied straight out?

Re-encoded, always — including when the source track is already AC-3. The audio is decoded and passed through the AC-3 encoder at the bitrate your settings resolve to, which means a second generation of lossy compression. If the source is already AC-3 at a bitrate you are happy with, keep it as high as the preset ladder allows to minimise what that second pass costs you.

What bitrate should I actually choose?

For a stereo soundtrack, 192 or 224 kbps is what commercial DVDs used and is transparent for most material. For 5.1, 384 or 448 kbps are the standard disc rates. The 640 kbps the Highest preset produces is legal but wasteful — you are spending nearly three times the bits a disc would for material that was already lossily compressed before you got it. Pick Constant Bitrate to set these exactly.

Why is the output file an elementary stream rather than a container?

Because that is what .ac3 means: raw AC-3 frames with no wrapper. It is exactly what a DVD or Blu-ray authoring tool wants as an audio asset, which is the main reason to produce one. The downside is that there is nowhere to store a title, artist or chapter marker, and some general-purpose media players will not open a bare .ac3 at all — VLC and ffmpeg-based tools will.

Can I take just one scene's audio instead of the whole file?

Yes, with the Trim group on this page. Set a start time and a duration in seconds, or use the HH:MM:SS.sss form for precision, and only that span is encoded. Trimming here also means the whole file is not run through the encoder, so long sources finish faster. To cut the video itself instead, video-cutter accepts .mpeg2 directly.

What if I want a normal music or podcast file rather than AC-3?

AC-3 is a delivery format for disc and broadcast, not a general listening format. For anything you intend to play on a phone or in a music library, MPEG-2 to MP3 is far more widely supported, and MPEG-2 to WAV gives you an uncompressed track for editing. Choose AC-3 when something downstream specifically asks for it.