Convert J2B to FLAC — Free Online Tool
Convert J2B game audio files from Jazz Jackrabbit 2 into lossless FLAC archives. This tool decodes the ASYLUM Music Format wrapped inside J2B's header and re-encodes it using the FLAC codec, preserving full audio fidelity without any additional quality loss.
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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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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
J2B files are module-style audio tracks used exclusively by Jazz Jackrabbit 2. They consist of a proprietary header wrapping an ASYLUM Music Format (AMF) payload, which itself encodes music using sample-based sequencing — not a continuous PCM stream. FFmpeg decodes this module music by rendering the sequenced instruments and samples into a linear PCM audio stream. That rendered PCM is then encoded with the FLAC codec at compression level 5, which applies lossless compression (no audio data is discarded). The result is a standard FLAC file that any modern audio player can read, containing the fully rendered game music as a permanent, playback-ready audio track.
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, executing entirely within your browser with no server involvement. |
-i input.j2b
|
Specifies the input J2B file. FFmpeg detects the Jazz Jackrabbit 2 container, strips the proprietary header, and passes the embedded ASYLUM Music Format data to its module audio decoder for rendering. |
-c:a flac
|
Selects the FLAC encoder for the audio stream. This encodes the PCM audio rendered from the J2B module into a lossless FLAC bitstream, replacing the original game-specific format with a universally supported open standard. |
-compression_level 5
|
Sets FLAC's compression effort to level 5 on a scale of 0–8. This is the default balanced setting — it produces a reasonably compact file without the significantly longer encoding time required by levels 7 or 8. All levels are lossless; this only affects file size and speed. |
output.flac
|
Defines the output filename and container. The .flac extension tells FFmpeg to write a native FLAC file, which is readable by virtually all modern audio players, DAWs, and archival tools. |
Common Use Cases
- Archiving the Jazz Jackrabbit 2 soundtrack in a universally readable, lossless format for long-term preservation after the original game files degrade or become inaccessible.
- Preparing J2B music tracks for use in video essays or retrospectives about 90s platformer games, where editors need standard audio formats their DAWs can import.
- Ripping specific level themes from J2B files to create a personal lossless music library of the Jazz Jackrabbit 2 OST without any generation loss.
- Converting J2B tracks to FLAC as an intermediate step before further processing — such as looping, pitch-shifting, or remixing — in professional audio software that doesn't support module formats.
- Extracting and preserving the rendered audio from custom or fan-made J2B music mods created for Jazz Jackrabbit 2, ensuring the compositions survive independently of the game engine.
- Providing lossless source files for streaming or uploading game music to archival platforms like the Internet Archive, where FLAC is preferred over lossy formats.
Frequently Asked Questions
The FLAC encoding step itself is entirely lossless — whatever PCM audio FFmpeg renders from the J2B file is stored in FLAC without any further degradation. However, J2B files use sample-based sequencing via the ASYLUM Music Format, so the rendered output depends on how FFmpeg interprets the module's instruments and samples. The rendered audio is an accurate representation of the module, and once in FLAC form, no quality is lost in that encoding stage.
J2B files store music as sequenced instructions — essentially a score plus a small set of instrument samples — which is extremely compact. When FFmpeg converts the J2B, it renders those instructions into a full linear PCM audio stream (like a .wav file), then compresses that with FLAC. Even with FLAC's lossless compression, a rendered audio stream is orders of magnitude larger than the original sequenced module data. A J2B file of a few hundred kilobytes can easily produce a FLAC file of several megabytes.
No. Jazz Jackrabbit 2 handles looping at the game engine level, using loop point metadata embedded in the J2B or AMF structure. When FFmpeg renders the module to PCM, it produces a single linear playback of the track and does not replicate the in-game looping behavior. If you need a looping FLAC file, you would need to manually identify the loop points and either use additional tools to embed loop metadata or duplicate the looping section in an audio editor.
Yes. The -compression_level flag accepts values from 0 to 8. Level 0 compresses the least (fastest encoding, largest file), while level 8 compresses the most (slowest encoding, smallest file). All levels are fully lossless — changing this flag only affects file size and encoding speed, never audio quality. For example, to maximize compression you would use -compression_level 8 in place of the default -compression_level 5.
The single-file command shown here processes one J2B at a time. To batch convert an entire folder of J2B files on a desktop system, you can use a shell loop. On Linux or macOS: for f in *.j2b; do ffmpeg -i "$f" -c:a flac -compression_level 5 "${f%.j2b}.flac"; done. On Windows Command Prompt: for %f in (*.j2b) do ffmpeg -i "%f" -c:a flac -compression_level 5 "%~nf.flac". The browser tool processes files individually.
J2B and the underlying ASYLUM Music Format carry very limited metadata — typically just an embedded song title or author string if one was included by the composer. FFmpeg will attempt to map any readable metadata tags to FLAC's Vorbis comment fields (e.g., TITLE, ARTIST). However, module format metadata is often absent or truncated in J2B files, so many conversions will produce a FLAC with minimal or no embedded tags. You may want to add tags manually after conversion using a tool like MusicBrainz Picard or Kid3.
Technical Notes
J2B is a niche, game-specific container created for Jazz Jackrabbit 2 by Epic MegaGames. It wraps the ASYLUM Music Format (AMF), itself a variant of the broader family of tracker/module audio formats popular in DOS-era games. FFmpeg's module decoder renders the sequenced playback — mixing the sample-based instruments according to the AMF pattern data — into interleaved PCM at a fixed sample rate (commonly 44100 Hz). Because the rendering is done in software, the output is deterministic but does not perfectly replicate every game engine's own audio mixer quirks. FLAC at compression level 5 is the standard balanced setting: it achieves roughly 50–60% of the compression that level 8 offers, but encodes significantly faster, making it appropriate for the rendered audio sizes typical of short game tracks. FLAC supports Vorbis comment metadata, cue sheets, and ReplayGain tags, none of which are populated automatically from J2B sources, so post-conversion tagging is recommended for library use. There are no video streams, subtitle tracks, or chapter markers in either format, so the conversion is a straightforward audio-only pipeline.