Extract Audio from VOB to AC3 — Free Online Tool
Extract the Dolby Digital AC3 audio track directly from a VOB file — the native container format used on DVD-Video discs. Since VOB files typically store audio as AC3 already, this tool performs a lossless stream copy, preserving the original surround sound quality without any re-encoding.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your VOB file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
VOB files on DVD-Video discs almost universally store their audio as AC3 (Dolby Digital), typically in 5.1 surround sound at 192–448 kbps. Because the source and output formats share the same AC3 codec, FFmpeg can extract the audio stream directly without transcoding — meaning no quality is lost in the process. The video stream is discarded entirely using the -vn flag, and the raw AC3 bitstream is written into a standalone .ac3 file. If your VOB happens to contain a non-AC3 audio track (such as AAC or MP3), FFmpeg will re-encode it to AC3 at the specified bitrate.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser version of this tool, this runs via FFmpeg.wasm (WebAssembly), executing the same logic client-side without uploading your file to any server. |
-i input.vob
|
Specifies the input VOB file — the MPEG Program Stream container used by DVD-Video discs, which typically contains MPEG-2 video, AC3 Dolby Digital audio, and optional subtitle streams. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the MPEG-2 video stream in the VOB. Since we only want the AC3 audio, this prevents any video data from being written to the output file. |
-c:a ac3
|
Sets the audio codec to AC3 (Dolby Digital). When the source VOB already contains AC3 audio, FFmpeg performs a stream copy rather than re-encoding, preserving the original bitrate and channel layout exactly. |
-b:a 192k
|
Specifies an audio bitrate of 192 kbps, which applies only if FFmpeg needs to transcode the audio (e.g., if the VOB contains AAC or MP3 instead of AC3). For native AC3 stream copies, the original disc bitrate is used and this flag has no effect. |
output.ac3
|
The output filename with the .ac3 extension, which signals a raw Dolby Digital Elementary Stream. This format contains only the audio bitstream with no container overhead, making it suitable for direct playback or muxing into MKV, MP4, or Blu-ray containers. |
Common Use Cases
- Ripping the Dolby Digital 5.1 surround sound track from a DVD VOB file to use in a home theater system or AV receiver that accepts AC3 input
- Archiving the original audio track from a DVD before editing or repackaging the video, preserving the unmodified Dolby Digital bitstream
- Extracting dialogue or a film score from a VOB file for audio analysis, subtitling work, or accessibility review without needing the full video
- Preparing AC3 audio for muxing into a new MKV or MP4 container after re-encoding the video, keeping the original DVD audio untouched
- Isolating a specific language audio track from a multi-track VOB file for use in dubbing or localization projects
- Extracting the audio from a DVD-authored VOB for use in Blu-ray authoring workflows that require a standalone AC3 stream
Frequently Asked Questions
In most cases, no. VOB files from DVD-Video discs almost always store audio natively as AC3 (Dolby Digital), so FFmpeg performs a direct stream copy rather than re-encoding. The extracted .ac3 file is a bit-for-bit copy of the original audio data from the disc. Quality loss would only occur if your VOB contains a non-AC3 audio codec, which would require transcoding.
By default, FFmpeg selects the first audio track in the VOB file, which is typically the primary language track. If your DVD VOB contains multiple audio streams (e.g., English 5.1, French stereo, director's commentary), you can target a specific one by adding '-map 0:a:1' to select the second audio track, or '-map 0:a:2' for the third, and so on. The tool on this page extracts the default track, but you can use the displayed FFmpeg command locally to specify the exact stream you need.
When the source audio is already AC3 and copied without re-encoding, the output bitrate matches the original — the -b:a flag only applies when transcoding is required. If re-encoding does occur (e.g., from a VOB with an AAC track), the default output bitrate is 192k. To change this, modify the FFmpeg command shown on the page by replacing '192k' with a supported AC3 bitrate such as 384k or 448k, which are common for DVD-quality 5.1 audio.
Most full-featured media players including VLC, MPC-HC, and Kodi can play raw .ac3 files directly. However, some lightweight players and mobile apps may not recognize the bare .ac3 container. If compatibility is a concern, consider muxing the extracted AC3 track into an MKV or MP4 container using FFmpeg, which will preserve the Dolby Digital audio while wrapping it in a universally recognized format.
On Linux or macOS, you can loop over all VOB files in a directory with: for f in *.vob; do ffmpeg -i "$f" -vn -c:a ac3 -b:a 192k "${f%.vob}.ac3"; done. On Windows Command Prompt, use: for %f in (*.vob) do ffmpeg -i "%f" -vn -c:a ac3 -b:a 192k "%~nf.ac3". This is especially useful when you have multiple VOB files from a DVD (VTS_01_1.vob, VTS_01_2.vob, etc.) that you want to process in sequence.
Yes. When FFmpeg copies the AC3 stream directly from the VOB without re-encoding, the full channel layout — including the 5.1 configuration of front left, front right, center, LFE (subwoofer), surround left, and surround right — is preserved exactly as encoded on the original DVD. The surround sound metadata embedded in the Dolby Digital bitstream is carried over intact to the output .ac3 file.
Technical Notes
VOB files use the MPEG Program Stream container and are subject to DVD sector formatting and navigation data, which FFmpeg handles by accepting '-f vob' as a format hint when auto-detection is ambiguous. The AC3 codec supports bitrates from 96k up to 640k in the .ac3 container, with DVD-Video typically using 192k for stereo and 384k–448k for 5.1 mixes. When extracting from a VOB, subtitle streams (VobSub/MPEG DVD subtitles) and chapter markers present in the VOB are not carried over to the .ac3 output, as the AC3 format supports neither. If the source VOB contains multiple audio streams or a non-AC3 audio codec like AAC (rare in DVD-Video but possible in authored discs), the tool will transcode to AC3 at 192k, which introduces a generation of lossy encoding. For large DVD rips split across multiple VOB files (e.g., VTS_01_1.vob through VTS_01_4.vob), it is advisable to concatenate them first using FFmpeg's concat demuxer before extracting audio to get a continuous, uninterrupted AC3 file.