Extract Audio from VOB to M4B — Free Online Tool
Extract audio from DVD VOB files and convert it to M4B audiobook format, transcoding the AC3 (Dolby Digital) audio track to AAC and packaging it in an MPEG-4 container with chapter and bookmarking support. Ideal for ripping spoken-word DVD content — lectures, audiobooks on disc, or recorded performances — into a format native to Apple Books and podcast apps.
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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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, and subtitle streams in a DVD-specific container. This tool discards the video and subtitle streams entirely, then transcodes the AC3 audio to AAC — the native codec for MPEG-4 audio containers. The resulting audio is wrapped in an M4B file with the -movflags +faststart flag, which relocates the MOOV atom to the beginning of the file for immediate playback and streaming. Because AC3 and AAC are both lossy formats, this is a lossy-to-lossy transcode, meaning a small additional generation of quality loss occurs. The M4B container supports chapters and bookmarking, which makes it uniquely suited for long-form spoken-word content ripped from DVD.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program. In this browser-based tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm) — no data is sent to a server. |
-i input.vob
|
Specifies the input VOB file. FFmpeg reads the MPEG-2 Program Stream container and identifies the multiplexed video, AC3 audio, and subtitle streams inside. |
-vn
|
Disables video output entirely, discarding the MPEG-2 video stream from the VOB. Since M4B is a pure audio container, no video data is written to the output file. |
-c:a aac
|
Transcodes the audio from the VOB's AC3 (Dolby Digital) stream to AAC using FFmpeg's built-in AAC encoder. AAC is the native audio codec for the M4B/MPEG-4 container and is required for Apple Books and podcast app compatibility. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second. This is appropriate for spoken-word content like audiobooks and lectures; for music or higher-fidelity source material, increasing this to 192k or 256k will preserve more detail. |
-movflags +faststart
|
Moves the MOOV atom (the file's structural metadata index) to the beginning of the M4B file. This allows audiobook players and podcast apps to begin playback and seek through the file immediately, without needing to read to the end of the file first. |
output.m4b
|
The output filename with the .m4b extension, which signals to Apple Books, iTunes, and compatible podcast apps that this is an audiobook file with bookmarking support — distinct from a plain .m4a audio file. |
Common Use Cases
- Ripping a DVD lecture series or university course disc to M4B so it can be listened to in Apple Books with chapter navigation and playback position bookmarking
- Converting a spoken-word audiobook released on DVD-Video into a format compatible with iPhone, iPad, and iPod audiobook libraries
- Extracting the audio commentary track from a DVD VOB file and packaging it as an M4B podcast episode for offline listening
- Archiving recorded stage performances or comedy specials from DVD into a portable M4B audio format for listening without video
- Converting DVD-based language learning courses — which often ship as VOB files — to M4B so learners can resume exactly where they left off using bookmarking
- Stripping audio from a recorded sermon, conference talk, or educational DVD to distribute as an M4B file compatible with podcast apps
Frequently Asked Questions
Yes, a small degree of additional quality loss is unavoidable. VOB files typically store audio as AC3 at bitrates between 192k and 448k, and this tool transcodes that to AAC at 128k by default. Since both AC3 and AAC are lossy codecs, you are performing a lossy-to-lossy transcode. For spoken-word content like audiobooks or lectures, 128k AAC is generally indistinguishable from the source, but if you are converting music or high-fidelity content you can increase the bitrate in the FFmpeg command using -b:a 192k or higher.
By default, FFmpeg selects the first audio stream it finds in the VOB file, which is typically the primary language track. If your VOB contains multiple AC3 audio streams and you need a specific one, you can modify the FFmpeg command by adding -map 0:a:1 to select the second audio track (zero-indexed), for example: ffmpeg -i input.vob -map 0:a:1 -vn -c:a aac -b:a 128k -movflags +faststart output.m4b.
Not automatically. DVD chapter data is stored as navigation metadata within the VOB and IFO file structure on the disc, not embedded in a single VOB file in a way FFmpeg can directly map to M4B chapter atoms. The M4B container does fully support chapters, but you would need to add chapter metadata manually after conversion using a tool like mp4chaps or Chapter and Verse. If your source is a full DVD rip with IFO files, tools like MakeMKV can first extract structured chapter data before you convert.
Change the -b:a 128k value to a higher bitrate. For spoken-word content, 128k AAC is typically sufficient, but for music or high-quality source audio you can use -b:a 192k or -b:a 256k. The M4B format supports AAC bitrates up to 320k. Keep in mind that because the source AC3 audio is already lossy, raising the output bitrate beyond the effective quality of the source will increase file size without recovering lost detail.
The single-file command shown here processes one VOB at a time. For a full DVD rip that is split across multiple VOB files (e.g., VTS_01_1.VOB, VTS_01_2.VOB), you can concatenate them first using FFmpeg's concat demuxer: create a text file listing each VOB, then run ffmpeg -f concat -safe 0 -i filelist.txt -vn -c:a aac -b:a 128k -movflags +faststart output.m4b. This produces a single continuous M4B from the entire disc's audio content.
The -movflags +faststart flag moves the MOOV atom — the metadata index that describes the file's structure — from the end of the file to the beginning. Without it, an M4B player would need to download or read the entire file before it can begin playback. With +faststart, apps like Apple Books, podcast clients, and web players can begin playing the file immediately and accurately seek through it before it is fully loaded. For audiobook files that may be several hundred megabytes, this makes a meaningful practical difference in usability.
Technical Notes
VOB files are not standalone audio containers — they are MPEG-2 Program Stream wrappers tightly coupled to the DVD-Video specification, and FFmpeg requires the -f vob hint in some edge cases to parse them correctly. The audio in most DVD VOBs is AC3 (Dolby Digital) at 48kHz, commonly at 192k or 224k bitrate for standard DVD releases. When transcoding to AAC for M4B, FFmpeg uses its native AAC encoder, which produces solid quality at 128k and above for speech content. The M4B format is structurally identical to M4A — it is an MPEG-4 Part 14 container — but the .m4b extension signals to Apple software that the file is an audiobook, enabling bookmarking and shelving in Apple Books. Note that M4B does not support multiple audio tracks, so only one stream from the VOB is extracted. Subtitle streams present in the VOB are dropped entirely, as M4B has no subtitle support. ID3-style metadata such as title, author, and album art can be added to the M4B after conversion using tools like AtomicParsley or ffmpeg's -metadata flag.