Extract Audio from WTV to J2B — Free Online Tool
Extract audio from WTV recorded TV files and convert it to J2B format using the LAME MP3 encoder. This tool strips the video stream entirely and re-encodes the audio track as MP3 at 128k bitrate — a niche but precise conversion for retro game audio workflows or archival curiosity involving the Jazz Jackrabbit 2 format.
to
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
WTV (Windows Television) files contain a multiplexed stream of video (typically H.264) and audio (typically AAC or MP3) recorded by Windows Media Center. During this conversion, the video stream is completely discarded using the -vn flag, and the audio stream — originally encoded as AAC in most WTV recordings — is decoded and then re-encoded from scratch using the LAME MP3 encoder into the J2B container. J2B is a file format native to Jazz Jackrabbit 2, based on the ASYLUM Music Format with a simple wrapper header, and its only supported codec is libmp3lame. Because the source audio is AAC and the target is MP3, this is a full transcode (not a remux), meaning each sample is decoded and re-encoded, which introduces a small amount of additional generation loss. The output bitrate defaults to 128k, which is adequate for voice and standard broadcast audio.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that handles all demuxing, decoding, encoding, and muxing for this WTV-to-J2B conversion. |
-i input.wtv
|
Specifies the input file — a WTV container produced by Windows Media Center, which typically holds an H.264 video stream and an AAC audio stream recorded from a digital broadcast. |
-vn
|
Disables video output entirely, discarding the H.264 (or MJPEG) video stream from the WTV recording so that only the audio track is processed. This is essential since J2B is a pure audio format with no video support. |
-c:a libmp3lame
|
Specifies the LAME MP3 encoder for the output audio track. Since WTV recordings typically store audio as AAC and J2B only supports MP3, this flag triggers a full decode-and-reencode transcode rather than a simple stream copy. |
-b:a 128k
|
Sets the MP3 output bitrate to 128 kilobits per second, the default for J2B output. This is a reasonable quality level for broadcast speech and general audio, though it will lose some fidelity compared to the original AAC stream due to the codec change. |
output.j2b
|
Defines the output filename with the .j2b extension, which tells FFmpeg to wrap the encoded MP3 audio in the J2B container format used by the Jazz Jackrabbit 2 game engine. |
Common Use Cases
- Extracting the audio track from a Windows Media Center recording of a TV broadcast to use as a music or sound source in a Jazz Jackrabbit 2 custom level mod
- Archiving the audio commentary or soundtrack from a recorded TV special into a J2B file as part of a retro gaming audio collection
- Pulling dialog or music from a WTV DVR recording to analyze or sample for a game audio project that targets the J2B format
- Converting a Windows Media Center-recorded concert broadcast into a J2B file to experiment with custom in-game music replacement in Jazz Jackrabbit 2
- Testing FFmpeg's ability to write J2B-wrapped MP3 output from broadcast source material as part of a retro format compatibility study
- Extracting a specific audio track from a multi-audio WTV recording (e.g., a secondary language track) and packaging it into a J2B file for game modding purposes
Frequently Asked Questions
Yes, some quality loss is expected. Most WTV recordings store audio as AAC, which is a more efficient codec than MP3 at equivalent bitrates. Converting AAC to MP3 is a transcode — the audio is fully decoded and then re-encoded — so you incur generation loss from both the original AAC compression and the new MP3 compression. At 128k, the result is acceptable for speech and general broadcast audio, but audiophiles or those working with music recordings may want to raise the bitrate to 192k or 256k to minimize degradation.
J2B is a proprietary audio container used exclusively by the Jazz Jackrabbit 2 game engine, wrapping an ASYLUM Music Format or MP3 stream in a simple binary header. It is not a general-purpose audio format, so standard media players like VLC or Windows Media Player will not open it without specialized plugins or tools. The format is primarily useful for Jazz Jackrabbit 2 modding and custom level creation, not for everyday listening or distribution.
By default, FFmpeg selects the first audio stream it encounters in the WTV file, which is typically the primary language track. If your recording contains multiple audio tracks — common in broadcast DVR recordings with secondary language or descriptive audio streams — you can specify a particular track using the -map flag in the FFmpeg command, such as -map 0:a:1 to select the second audio stream. The tool's default command does not include a -map flag, so it will always extract the default (first) audio track.
The audio bitrate is controlled by the -b:a flag in the command. The default is 128k, but J2B supports 64k, 128k, 192k, 256k, and 320k. To increase quality, replace 128k with a higher value such as -b:a 256k. To reduce file size for voice-only recordings, you could use -b:a 64k. Simply edit the command displayed on this page and run it locally in your terminal: ffmpeg -i input.wtv -vn -c:a libmp3lame -b:a 256k output.j2b
No. J2B is a minimal container format designed for game engine use, and it does not support embedded metadata tags like title, artist, or date. Any EPG metadata embedded in the WTV file — such as the program name, channel, or recording timestamp stored by Windows Media Center — will be lost during conversion. If preserving this metadata matters to you, consider extracting the audio to a more capable format like MP3 with ID3 tags or FLAC before any further processing.
FFmpeg does not natively support batch processing in a single command, but you can easily script it. On Windows, use a batch file: for %f in (*.wtv) do ffmpeg -i "%f" -vn -c:a libmp3lame -b:a 128k "%~nf.j2b". On Linux or macOS, use a shell loop: for f in *.wtv; do ffmpeg -i "$f" -vn -c:a libmp3lame -b:a 128k "${f%.wtv}.j2b"; done. This is especially useful if you have a folder of Windows Media Center recordings you want to process in bulk.
Technical Notes
WTV files produced by Windows Vista/7 Media Center typically encode video in H.264 and audio in AAC (often at 192k or 256k from digital broadcast sources), though some recordings may use MP3 audio depending on the broadcast stream. The J2B format is an unusual conversion target: it is not a standard audio container but rather a game-specific wrapper for the ASYLUM Music Format used in Jazz Jackrabbit 2, and FFmpeg's support for writing it is limited to the libmp3lame codec. Because the source AAC audio must be fully decoded before being re-encoded as MP3, this is not a lossless extraction — it is a lossy-to-lossy transcode. The J2B container does not support chapters, subtitles, multiple audio tracks, or metadata, so all of those elements present in the source WTV file are silently dropped. WTV files can be quite large (multi-gigabyte for long recordings), making the browser-based tool's 1GB limit a practical constraint for longer broadcasts; the displayed FFmpeg command is particularly useful for processing full-length movie or sports recordings locally.