Convert VOB to FLAC — Free Online Tool
Extract and preserve the audio from a DVD VOB file as a lossless FLAC file, converting the AC3 (Dolby Digital) or other audio streams into a format ideal for archiving, music playback, and high-fidelity listening. Because VOB uses lossy AC3 audio and FLAC uses lossless compression, the output is a bit-perfect encode of the source audio — no further quality is lost in the process.
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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 from DVD discs typically contain multiplexed MPEG-2 video, AC3 (Dolby Digital) audio, subtitle streams, and sometimes multiple audio tracks. This conversion strips away the video, subtitle, and container data entirely, isolating only the first audio stream and re-encoding it using the FLAC codec. FLAC applies lossless compression — meaning every sample in the output file is mathematically identical to the input audio samples decoded from the AC3 stream. Since AC3 is a lossy format, the original lossy compression artifacts are preserved in the FLAC output, but no additional quality degradation occurs. The result is a compact, seekable audio file that faithfully represents the AC3 audio as decoded.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser version, this runs via FFmpeg.wasm compiled to WebAssembly, so no installation is needed and no files leave your device. |
-i input.vob
|
Specifies the input VOB file. FFmpeg probes the VOB container to identify all multiplexed streams — typically an MPEG-2 video stream, one or more AC3 audio streams, and possibly DVD subtitle streams. |
-c:a flac
|
Sets the audio codec to FLAC. FFmpeg will decode the source AC3 audio from the VOB into raw PCM samples and then re-encode those samples using the FLAC lossless encoder, producing a mathematically exact representation of the decoded audio. |
-compression_level 5
|
Sets FLAC's compression effort to level 5 on a scale of 0–8. All levels produce bit-identical audio output; this setting only affects the trade-off between encoding speed and output file size. Level 5 is the FLAC default and suits most archival and playback use cases. |
output.flac
|
Defines the output filename with the .flac extension. FFmpeg uses this extension to confirm the FLAC container format, which will hold the lossless audio stream with no video, subtitles, or DVD menu data. |
Common Use Cases
- Archive the audio soundtrack from a DVD concert or live performance film in lossless quality for long-term storage
- Extract a film score or original soundtrack from a DVD VOB file into FLAC for use in a high-resolution music library
- Rip dialogue or commentary tracks from a DVD to FLAC for transcription or accessibility purposes
- Convert the audio from a DVD language-learning disc into FLAC for offline listening without video
- Preserve the multichannel AC3 audio from a DVD into a lossless format before further processing or downmixing
- Extract audio from a home movie DVD backed up as VOB files to create a standalone audio keepsake
Frequently Asked Questions
No additional quality is lost during this conversion. The AC3 audio in the VOB file is decoded and then re-encoded using FLAC's lossless algorithm, which means the decoded audio samples are stored exactly as-is — no lossy compression is applied in the FLAC stage. However, since AC3 itself is a lossy format, any compression artifacts already present in the original DVD audio are preserved in the output. FLAC simply ensures no further degradation occurs.
It depends on the source. If the VOB file contains a 5.1 AC3 audio stream, FFmpeg will decode all six channels and encode them into the FLAC file, preserving the multichannel layout. FLAC fully supports multichannel audio, so no downmixing to stereo occurs by default. You can verify the channel layout of your output using a tool like MediaInfo or by adding '-af 'channelmap'' to the FFmpeg command if you need a specific configuration.
By default, FFmpeg selects the first audio stream it finds in the VOB file. DVD VOBs often contain multiple audio tracks for different languages or commentary. To target a specific track, you can add '-map 0:a:1' (for the second audio stream) or '-map 0:a:2' (for the third) to the command before the output filename. Run 'ffmpeg -i input.vob' first to list all detected streams and their indices.
The '-compression_level' flag controls how hard the FLAC encoder works to compress the audio data, ranging from 0 (fastest, largest file) to 8 (slowest, smallest file). Crucially, all levels produce bit-identical audio — the difference is only in file size and encoding speed. Level 5 is the default and offers a good balance. For archival use you might try level 8 for maximum compression, but the file size difference between levels is typically modest (a few percent), so level 5 is a sensible choice for most users.
To change the compression level, replace the '5' in '-compression_level 5' with a value between 0 and 8, for example '-compression_level 8' for maximum compression. To extract a specific audio track, insert a mapping flag before the output filename, like: 'ffmpeg -i input.vob -map 0:a:1 -c:a flac -compression_level 5 output.flac'. This selects the second audio stream (index 1). You can chain both changes in the same command.
This is expected and reflects the nature of lossless versus lossy compression. The AC3 audio in a VOB file is highly compressed lossy audio, often at 192–448 kbps. FLAC, while lossless, typically encodes PCM audio at much higher bitrates (600–1200 kbps for stereo, more for 5.1). Additionally, the VOB file contains video, which dominates its file size — so the FLAC audio-only file may actually be smaller than the full VOB. If file size is a concern, consider using the '-compression_level 8' flag to maximize FLAC's compression.
Technical Notes
VOB files do not always begin with a clean audio stream header, which can cause FFmpeg to take a moment to probe the file before processing begins — this is normal. The default audio codec in VOB is AC3 (Dolby Digital), but some DVDs use DTS, LPCM, or even MPEG audio; FFmpeg will detect and decode whichever codec is present before encoding to FLAC. Subtitle streams (typically DVD bitmap-based SUB/IDX format) and chapter data are not carried over into FLAC, as the format does not support them. FLAC does support Vorbis-style metadata tags (title, artist, album, etc.), but these will not be populated automatically from the VOB source — they must be added manually using a tag editor after conversion. If your VOB is part of a multi-file DVD rip (VTS_01_1.VOB, VTS_01_2.VOB, etc.), you may want to concatenate them first using FFmpeg's concat demuxer to produce a single uninterrupted FLAC file rather than converting each VOB separately.