Extract Audio from VOB to FLAC — Free Online Tool
Extract lossless audio from DVD VOB files by converting the AC3 (Dolby Digital) audio track to FLAC — a lossless open format that preserves every bit of the original audio data. Ideal for archiving DVD soundtracks or dialogue without any quality degradation from 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
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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 contain multiplexed MPEG-2 video, AC3 (Dolby Digital) audio, and often subtitle streams packed together in the DVD-Video container format. This tool demuxes the VOB file to strip away the video and subtitle streams entirely, then transcodes the AC3 audio to FLAC. Because AC3 is a lossy format and FLAC is lossless, this is technically a lossy-to-lossless transcode — meaning FLAC will perfectly preserve the AC3 decoded audio with no further generation loss, but the original AC3 compression artifacts (from the DVD mastering process) are already baked in. The output FLAC file is decoded from AC3 at full fidelity and then re-encoded losslessly, making it ideal for archiving or further editing without any additional quality loss.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In this browser-based tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm) — your VOB file is never uploaded to a server. |
-i input.vob
|
Specifies the input VOB file. FFmpeg reads this MPEG Program Stream container, identifying all multiplexed streams including MPEG-2 video, AC3 audio, and any subtitle streams present in the DVD VOB structure. |
-vn
|
Disables video output entirely, instructing FFmpeg to ignore the MPEG-2 video stream in the VOB. This is essential for audio-only extraction — without it, FFmpeg would attempt to include video in the output, which FLAC cannot contain. |
-c:a flac
|
Sets the audio codec to FLAC (Free Lossless Audio Codec). The AC3 Dolby Digital audio decoded from the VOB is re-encoded into FLAC, preserving the exact decoded waveform losslessly with no further quality degradation. |
-compression_level 5
|
Sets the FLAC compression level to 5 on a scale of 0–8. This controls only the encoding speed and output file size — not audio quality, which is identical at every level. Level 5 is the FLAC default, offering a practical balance between fast processing and compact file size. |
output.flac
|
The name of the output file. The .flac extension tells FFmpeg to write a standard FLAC audio file containing the losslessly encoded audio extracted from the source VOB. |
Common Use Cases
- Archiving the audio from DVD concert recordings or live performances as lossless FLAC files for long-term storage and playback on audiophile hardware
- Extracting AC3 Dolby Digital audio from a DVD VOB backup to edit or remix in a DAW that works better with lossless FLAC than compressed AC3
- Ripping the audio commentary track from a DVD VOB file to listen to or archive separately, without re-encoding through multiple lossy generations
- Converting DVD film scores or soundtracks stored in VOB format into FLAC for use in music library software like MusicBrainz Picard or foobar2000
- Pulling dialogue or spoken-word audio from a DVD educational or lecture disc into FLAC for transcription or subtitle generation workflows
- Preparing DVD audio content for lossless format comparison or quality analysis, where AC3-to-FLAC retains the exact decoded waveform without further lossy compression
Frequently Asked Questions
No — FLAC cannot recover quality lost during the original AC3 encoding on the DVD. AC3 is a lossy format, so the compression artifacts introduced during DVD mastering are already embedded in the audio signal. What FLAC does is capture the decoded AC3 audio perfectly and store it without any further quality loss, making it the ideal format for archiving or editing without adding a second generation of lossy compression.
The AC3 audio track inside a VOB is heavily compressed using Dolby Digital's lossy codec, which is very bandwidth-efficient. FLAC, while compressed, uses lossless compression — it stores the full decoded PCM waveform. A typical AC3 stream at 192–448 kbps will expand significantly when decoded and re-encoded as FLAC, often resulting in files 3–5 times larger. This size increase is the cost of lossless fidelity.
By default, FFmpeg selects the first audio stream in the VOB file, which is typically the primary language track. If your VOB contains multiple audio tracks — common on multilingual DVD releases — you can specify a particular stream using the '-map' flag, such as '-map 0:a:1' to select the second audio track. The FFmpeg command displayed on this page can be copied and modified locally for this purpose.
The '-compression_level 5' flag controls how aggressively FLAC compresses the audio data. Valid values range from 0 (fastest encoding, largest file) to 8 (slowest encoding, smallest file). Critically, changing this value has absolutely no effect on audio quality — all compression levels produce bit-identical decoded output. Using '-compression_level 0' is useful for very fast extraction, while '-compression_level 8' gives you the smallest possible lossless file at the cost of encoding time.
For a full DVD rip consisting of multiple numbered VOB files (VTS_01_1.VOB, VTS_01_2.VOB, etc.), you can concatenate them using FFmpeg's concat demuxer rather than processing each file individually. Alternatively, many users combine the VOB files first using a tool like cat (on Linux/macOS) and then run the FFmpeg command on the merged file. The single-file command shown here works best for individual VOB segments under 1GB.
VOB files do not store conventional audio metadata tags like ID3 or Vorbis comments — DVD metadata is encoded in the IFO control files rather than the VOB streams themselves. As a result, the extracted FLAC file will typically have no embedded title, artist, or album tags. You will need to add metadata manually using a tag editor such as Mp3tag, beets, or foobar2000 after extraction.
Technical Notes
VOB files are a specialised container based on MPEG Program Stream (MPEG-PS), and FFmpeg requires the '-f vob' format hint for reliable demuxing in some cases. The audio in DVD VOB files is most commonly AC3 (Dolby Digital) at 48 kHz sample rate with 2.0 stereo or 5.1 surround channel layouts. FLAC fully supports multi-channel audio, so 5.1 AC3 sources will be decoded and stored as 6-channel FLAC without downmixing. One known limitation: VOB files with copy-protection (CSS encryption) cannot be processed directly and must be decrypted first using a tool like HandBrake or MakeMKV before FFmpeg can read the audio streams. Additionally, if a VOB contains multiple audio streams encoded at different bitrates or in different formats (e.g., one AC3 track and one DTS track), only the default stream is extracted unless you explicitly map a specific stream. The '-compression_level 5' default balances encoding speed and file size, producing output identical in audio quality to any other compression level.