Convert DVR to J2B — Free Online Tool
Convert DVR surveillance or broadcast recordings to J2B audio format by extracting and encoding the audio stream using the LAME MP3 encoder. This tool strips the video entirely and outputs a J2B file — the ASYLUM Music Format container used by Jazz Jackrabbit 2 — making it a niche but precise conversion for game audio modding or archival purposes.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your DVR file here
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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
DVR files typically carry H.264 video alongside AAC or MP3 audio, recorded from digital video recorders used in surveillance or broadcast capture systems. During this conversion, the video stream is completely discarded — no video re-encoding takes place. The audio stream is extracted and transcoded to MP3 using the libmp3lame encoder, then wrapped in the J2B container, which is a thin header layer over the ASYLUM Music Format as used by the Jazz Jackrabbit 2 game engine. Because J2B supports only audio and only the libmp3lame codec, FFmpeg handles this as a straightforward audio-only transcode. If the source DVR file used AAC audio, it will be decoded and re-encoded to MP3; if it already used MP3 (libmp3lame), it will still be re-encoded to ensure proper J2B framing.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — the open-source multimedia processing engine that powers this conversion both in the browser via WebAssembly and locally on your desktop. |
-i input.dvr
|
Specifies the input DVR file — a proprietary digital video recorder container that typically holds H.264 or MJPEG video alongside AAC or MP3 audio from surveillance or broadcast capture devices. |
-c:a libmp3lame
|
Sets the audio codec to libmp3lame, which encodes the extracted DVR audio as MPEG Layer 3 (MP3) — the only audio codec supported by the J2B output format in FFmpeg. |
-b:a 128k
|
Sets the MP3 audio bitrate to 128 kilobits per second, the default quality level for J2B output. This controls the trade-off between audio fidelity and file size; increase to 192k or 320k if the source DVR audio contains important detail such as speech or music. |
output.j2b
|
Specifies the output filename with the .j2b extension, telling FFmpeg to write the encoded MP3 audio into a J2B container — the ASYLUM Music Format wrapper used by Jazz Jackrabbit 2. |
Common Use Cases
- Game audio modders replacing or adding custom background music tracks in Jazz Jackrabbit 2 using real-world audio sourced from DVR recordings
- Archivists extracting audio commentary or broadcast speech from DVR surveillance footage and packaging it in J2B format for a retro game preservation project
- Developers testing J2B audio playback pipelines or game engine audio loaders using varied real-world audio content sourced from DVR captures
- Hobbyists creating custom J2B music packs for Jazz Jackrabbit 2 fan levels, using ambient or environmental audio captured via DVR as source material
- Researchers studying the ASYLUM Music Format who need sample J2B files generated from known, real-world audio sources like broadcast recordings
- Retro game community contributors converting captured TV or radio audio from DVR recordings into J2B tracks for use in open-source Jazz Jackrabbit 2 reimplementations like OpenJazz
Frequently Asked Questions
The J2B format was originally designed around the ASYLUM Music Format, which is a tracker-based module format — not a standard MP3 stream. FFmpeg can write files with a .j2b extension using libmp3lame, but the resulting file may not be fully compatible with the original Jazz Jackrabbit 2 engine, which expects tracker module data rather than a raw MP3 payload. This conversion is more appropriate for tools or engines that parse J2B as an MP3 wrapper rather than the strict ASYLUM tracker format. Always test output files with your target player or engine.
The video stream — typically H.264 encoded at whatever resolution the DVR captured — is completely dropped. FFmpeg does not re-encode or preserve it in any way. J2B is a purely audio format with no video container capability, so only the audio track from the DVR file is processed and written to the output.
Yes, a generation of lossy quality loss occurs. AAC audio from the DVR must be fully decoded back to PCM and then re-encoded to MP3 using libmp3lame at 128k by default. Both AAC and MP3 are lossy codecs, so decoding and re-encoding introduces additional compression artifacts compared to the original captured audio. If audio fidelity matters, increase the output bitrate to 192k or 320k using the -b:a flag.
Replace the -b:a 128k value in the command with your preferred bitrate. For example, use -b:a 192k or -b:a 320k for higher quality MP3 output, or -b:a 64k to reduce file size. The supported options for J2B output via libmp3lame are 64k, 128k, 192k, 256k, and 320k. Higher bitrates will produce larger files but closer audio fidelity to the original DVR recording.
Yes, on the command line you can use a shell loop to process multiple files. On Linux or macOS, run: for f in *.dvr; do ffmpeg -i "$f" -c:a libmp3lame -b:a 128k "${f%.dvr}.j2b"; done. On Windows with PowerShell, use: Get-ChildItem *.dvr | ForEach-Object { ffmpeg -i $_.FullName -c:a libmp3lame -b:a 128k ($_.BaseName + '.j2b') }. The browser-based tool processes one file at a time, so the FFmpeg command is especially useful for bulk workflows.
No. DVR-specific metadata such as recording timestamps, camera identifiers, and device information is embedded in the DVR container and is not preserved during conversion to J2B. The J2B format has no standardized metadata fields for this kind of information. The output file will contain only the encoded MP3 audio stream with the J2B header wrapper and no descriptive tags from the source recording.
Technical Notes
DVR is a proprietary container format with no single universal specification — different manufacturers implement it differently, which means FFmpeg's ability to demux the input depends on how closely the file follows common DVR conventions. The audio stream inside a DVR file is most commonly AAC or MP3 (libmp3lame), both lossy. J2B is a highly niche audio container originally associated with the Jazz Jackrabbit 2 game, wrapping the ASYLUM Music Format — a tracker module format. However, FFmpeg treats J2B output as an MP3 stream with a container header, which means the resulting file is technically an MP3 payload in a J2B wrapper rather than a true ASYLUM tracker module. This distinction matters: original Jazz Jackrabbit 2 software expects tracker data, not a PCM-derived MP3 stream, so compatibility with the original game is not guaranteed. The libmp3lame encoder used here produces standard MPEG Layer 3 audio at the specified bitrate, with no transparency, no subtitle track, and no chapter support — matching J2B's own format limitations. File sizes will be substantially smaller than the source DVR file since all video data is discarded and only the audio remains at a controlled bitrate.