Convert VOB to J2B — Free Online Tool
Convert VOB files from DVD-Video discs into J2B audio format, extracting the AC3 or MPEG audio stream and re-encoding it as MP3 using the LAME encoder. This tool strips the MPEG-2 video, subtitle, and menu data from the VOB container, isolating only the audio for output as a J2B file compatible with the Jazz Jackrabbit 2 game engine's ASYLUM Music Format wrapper.
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 are multiplexed containers holding MPEG-2 video, AC3 (Dolby Digital) or other audio streams, subtitle tracks, and DVD menu data. During this conversion, FFmpeg demuxes the VOB container to extract the audio stream — typically AC3 at 192–448 kbps — and discards all video, subtitle, and chapter data entirely. The extracted audio is then transcoded from AC3 to MP3 using the libmp3lame encoder at 128 kbps by default, and the result is wrapped with a J2B file extension. J2B is fundamentally an audio format tied to Jazz Jackrabbit 2's soundtrack system, so the output is a lossy MP3 stream with a J2B header structure. There is no video passthrough, no subtitle preservation, and no container-level remuxing — this is a full audio transcode from one lossy format (AC3) to another (MP3).
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg multimedia processing tool, which handles demuxing the VOB container, decoding the AC3 audio stream, and encoding the MP3 output for J2B. |
-i input.vob
|
Specifies the input VOB file. FFmpeg recognizes the .vob extension and applies the MPEG Program Stream / DVD demuxer to correctly parse the multiplexed MPEG-2 video, AC3 audio, and subtitle packet structure. |
-c:a libmp3lame
|
Selects the LAME MP3 encoder for the audio output stream, transcoding the source AC3 Dolby Digital audio from the VOB into an MP3 bitstream suitable for embedding in the J2B file. |
-b:a 128k
|
Sets the MP3 audio output bitrate to 128 kilobits per second. This is the default quality level for J2B output — sufficient for game audio use, though the source AC3 track (often 192–448 kbps) will lose some fidelity in the downward transcode. |
output.j2b
|
Defines the output filename and triggers FFmpeg to wrap the encoded MP3 audio in a J2B file. The .j2b extension tells FFmpeg to use the Jazz Jackrabbit 2 / ASYLUM Music Format muxer, discarding all video and subtitle streams from the original VOB. |
Common Use Cases
- Extracting the audio soundtrack from a DVD-ripped VOB file to create a J2B-compatible audio asset for Jazz Jackrabbit 2 custom level modding
- Pulling dialog or music from a VOB file captured off a DVD and converting it to an MP3-based format for archival or game modding pipelines that expect J2B files
- Converting legacy DVD audio commentary tracks stored in VOB format into a compact MP3-wrapped J2B file for use in game engine tools
- Stripping AC3 surround audio from a multi-track VOB file and downmixing it to stereo MP3 as part of a game asset preparation workflow
- Batch-processing VOB chapter files from a DVD rip to produce a series of J2B audio files corresponding to individual scenes or music cues for game level editors
Frequently Asked Questions
J2B is a purely audio format originating from the Jazz Jackrabbit 2 game engine — it has no capacity to store video, subtitles, or chapter data. When FFmpeg processes the VOB, it automatically discards all MPEG-2 video streams and DVD subtitle tracks, outputting only the re-encoded MP3 audio stream wrapped in the J2B structure. If you need the video, you would need to convert to a container format like MP4 or MKV instead.
Yes, some quality loss is inherent because this is a transcode between two different lossy codecs — AC3 and MP3. DVD VOB files typically carry AC3 audio at 192–448 kbps, and the default output here is MP3 at 128 kbps, which represents a significant bitrate reduction. For casual or game modding use this is usually acceptable, but for critical listening you should raise the output bitrate to 256k or 320k in the FFmpeg command using the -b:a flag.
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 and you need a specific one, you can add the -map flag to the FFmpeg command, for example '-map 0:a:1' to select the second audio stream. The J2B format supports only a single audio track, so only one stream can be included in the output.
The audio bitrate is controlled by the -b:a flag in the command. The default is 128k, but you can change it to values like 64k for smaller file sizes or 192k, 256k, or 320k for higher fidelity. For example, to get the best possible MP3 quality use: ffmpeg -i input.vob -c:a libmp3lame -b:a 320k output.j2b. Keep in mind that since the source AC3 audio is already lossy, the gains from very high bitrates are limited.
The single-file command shown on this page processes one VOB at a time, but you can adapt it for batch processing using a shell loop. On Linux or macOS, run: for f in *.vob; do ffmpeg -i "$f" -c:a libmp3lame -b:a 128k "${f%.vob}.j2b"; done. On Windows Command Prompt, use: for %f in (*.vob) do ffmpeg -i "%f" -c:a libmp3lame -b:a 128k "%~nf.j2b". This is especially useful when ripping individual chapter VOB files from a DVD.
No. J2B supports neither subtitles nor chapter markers — it is a minimal audio-only format. All DVD subtitle streams (typically stored as MPEG-2 bitmap overlays in the VOB) and any chapter timing data are silently discarded during conversion. If subtitle or chapter preservation is a requirement, you would need to target a different output format entirely.
Technical Notes
VOB files use the MPEG Program Stream container with a DVD-specific extension, and their audio is almost universally AC3 (Dolby Digital) at 48 kHz sample rate, though some VOBs carry LPCM, DTS, or MPEG audio instead. FFmpeg's VOB demuxer (-f vob, applied implicitly by the .vob extension) handles the DVD sector structure and packet parsing. The output J2B format is associated with Jazz Jackrabbit 2 and is based on the ASYLUM Music Format with a small proprietary header; FFmpeg writes the file with a .j2b extension and encodes the audio payload as MP3 via libmp3lame. Because both AC3 and MP3 are lossy codecs, this transcode introduces generation loss — artifacts from both compression stages can accumulate, particularly at the default 128 kbps output bitrate. The AC3 source is typically multichannel (5.1), and libmp3lame will downmix to stereo by default without explicit channel mapping instructions. No metadata from the VOB (DVD title, language tags, timestamps) is carried through to the J2B output, as the format has no standardized metadata container. Files over 1 GB — common for full DVD title VOBs — should be processed using the desktop FFmpeg command rather than the browser-based tool.