Extract Audio from VOB to M4A — Free Online Tool
Extract audio from DVD VOB files and save it as M4A, transcoding the AC3/Dolby Digital soundtrack to AAC — the native codec for iTunes, Apple Music, and iOS devices. Ideal for ripping music concerts, audiobooks, or any DVD audio content into a clean, portable audio file.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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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 store multiplexed MPEG-2 video, AC3 (Dolby Digital) audio, subtitle streams, and menu data in a single container. This tool strips the video and subtitle streams entirely, then transcodes the AC3 audio track to AAC and wraps it in an M4A (MPEG-4 audio) container. AC3 cannot be stored natively in M4A, so re-encoding is necessary — FFmpeg decodes the AC3 bitstream and re-encodes it as AAC at 128k bitrate by default. If the VOB contains multiple audio tracks (common on DVDs with multi-language audio), the first track is selected automatically. The output M4A file is significantly smaller than the original VOB because all video data is discarded.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary. In this browser-based tool, FFmpeg runs locally via WebAssembly (ffmpeg.wasm) — no file data leaves your machine. |
-i input.vob
|
Specifies the input VOB file. FFmpeg automatically detects the MPEG Program Stream container and identifies the multiplexed MPEG-2 video, AC3 audio, and subtitle streams inside it. |
-vn
|
Disables video output, ensuring that the MPEG-2 video stream from the VOB is completely discarded. This is essential since M4A is an audio-only container and cannot hold video data. |
-c:a aac
|
Transcodes the audio using FFmpeg's built-in AAC encoder. Since VOB audio is typically AC3 (Dolby Digital), which is incompatible with the M4A container, this re-encodes the audio stream to AAC — the native and default codec for M4A. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is a reasonable default for speech and general audio; for music concerts or high-fidelity DVD soundtracks, increasing this to 192k or 256k is recommended to better preserve the dynamic range of the original AC3 source. |
-vn
|
A second instance of the video-disable flag, reinforcing that no video stream should be written to the output. While redundant given the earlier '-vn', it acts as an explicit safeguard specific to audio-only output formats like M4A. |
output.m4a
|
The output filename with the .m4a extension, which tells FFmpeg to wrap the AAC-encoded audio in an MPEG-4 audio container — the standard format used by iTunes, Apple Music, and iOS for AAC audio files. |
Common Use Cases
- Ripping the audio from a DVD music concert or live performance to listen to on an iPhone or in Apple Music without carrying the disc
- Extracting the AC3 audio commentary track from a DVD VOB file to review or re-edit it in an audio editor like GarageBand or Logic Pro
- Converting a DVD audiobook or lecture series VOB into M4A files for playback in podcast apps or on Apple devices that don't support AC3
- Archiving the audio from home DVD recordings (e.g., family events recorded to DVD camcorder discs) into a smaller, modern format before the discs degrade
- Pulling the audio from a DVD-sourced film score or soundtrack disc into M4A for use in an iTunes or Apple Music library
- Extracting dialogue or narration audio from a DVD training video to repurpose as a standalone audio guide
Frequently Asked Questions
Yes, there is a generational quality loss because this conversion transcodes from one lossy format (AC3) to another (AAC). AC3 audio on DVDs is typically encoded at 192–448 kbps, and decoding then re-encoding to AAC at 128k will introduce some additional artifacts. In practice, AAC at 128k is very efficient and the result is generally indistinguishable from the source for casual listening, but audiophiles may prefer bumping the bitrate to 192k or 256k for critical material like music concerts.
FFmpeg selects the first audio stream by default, which is typically the primary language track on the DVD. If you need a specific track — for example, the DTS track or an alternate language — you can add the flag '-map 0:a:1' (for the second audio stream) to the FFmpeg command before the output filename. VOB files commonly carry multiple AC3 streams for different languages, so checking with 'ffprobe input.vob' first is a good way to identify stream indices.
M4A is an MPEG-4 container specifically designed to hold AAC audio, and it is the preferred format for Apple ecosystems including iTunes, Apple Music, and iOS devices. AC3 (Dolby Digital) is a surround-sound codec primarily designed for DVD and broadcast — it is not natively supported in M4A. The conversion re-encodes AC3 to AAC, which offers comparable quality at lower bitrates and has near-universal playback support across modern devices and platforms.
The bitrate is controlled by the '-b:a' flag in the command. The default is 128k, but you can increase it to 192k, 256k, or 320k for higher quality — useful for music or concert audio where detail matters. For example, replace '-b:a 128k' with '-b:a 256k' in the command. Keep in mind that because the source AC3 is already lossy, increasing the AAC bitrate beyond 192k yields diminishing returns.
Yes. On Linux or macOS, you can use a shell loop: 'for f in *.vob; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k -vn "${f%.vob}.m4a"; done'. On Windows Command Prompt, use: 'for %f in (*.vob) do ffmpeg -i "%f" -vn -c:a aac -b:a 128k -vn "%~nf.m4a"'. This is particularly useful when processing a full DVD rip that has been split into multiple VOB files (VTS_01_1.vob, VTS_01_2.vob, etc.).
Subtitle streams are dropped entirely — the '-vn' flag discards all non-audio streams, and M4A does not support subtitles regardless. DVD chapter data from VOB files is stored in the IFO sidecar files rather than inside the VOB itself, so chapter markers are not available during this conversion and will not appear in the M4A output. M4A does technically support chapters, but they would need to be added manually after the fact using a tool like mp4chaps or iTunes.
Technical Notes
VOB files use the MPEG Program Stream (PS) format and may contain AC3 (Dolby Digital 2.0 or 5.1), DTS, MPEG audio, or even PCM audio tracks depending on the disc authoring. This tool targets the default AC3 stream, which is the most common DVD audio codec. The AC3 to AAC transcode is inherently lossy-to-lossy, meaning audio quality is bounded by the original AC3 encode — increasing the AAC output bitrate cannot recover information lost in the original compression. M4A using AAC is not capable of carrying surround sound in the same way AC3 5.1 can; if the source is Dolby Digital 5.1, the AAC encoder will downmix or encode the surround channels, depending on FFmpeg's channel layout handling (stereo downmix is common by default). The '-vn' flag appears twice in the resolved command — once to suppress video output (a required flag for M4A) and once as a general safety measure; the first instance is the operative one. M4A supports iTunes-style metadata tags (title, artist, album, artwork) which can be added separately with FFmpeg's '-metadata' flags, but no metadata is copied from the VOB source since VOB files carry minimal embedded metadata. File sizes will be dramatically smaller than the source VOB: a 1GB VOB file may yield an M4A of only 40–80MB, since all video data is discarded and AAC is highly space-efficient.