Extract Audio from MTS to J2B — Free Online Tool
Extract audio from MTS camcorder footage and save it as a J2B file using the LAME MP3 encoder. MTS files from Sony and Panasonic AVCHD camcorders carry AC-3 or AAC audio streams inside an MPEG-2 Transport Stream container — this tool strips the H.264 video entirely and re-encodes the audio as MP3 wrapped in the J2B format used by Jazz Jackrabbit 2.
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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
MTS files store audio as either AC-3 (Dolby Digital) or AAC inside an MPEG-2 Transport Stream container. Because J2B is built on the ASYLUM Music Format and only supports MP3 audio via the LAME encoder, a full audio transcode is required — there is no stream-copy shortcut here. FFmpeg demuxes the transport stream, decodes the audio track (AC-3 or AAC), and re-encodes it to MP3 at the target bitrate using libmp3lame, then wraps the result in the J2B container structure. The H.264 video stream is discarded entirely with the -vn flag, so no video processing time is spent.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg media processing engine. In this browser-based tool, FFmpeg runs entirely as WebAssembly (FFmpeg.wasm) inside your browser — no file data is sent to a server. |
-i input.mts
|
Specifies the input MTS file — an AVCHD MPEG-2 Transport Stream from a Sony or Panasonic camcorder containing H.264 video and AC-3 or AAC audio. |
-vn
|
Disables video output entirely, discarding the H.264 video stream from the MTS file. This is essential for audio extraction and prevents FFmpeg from wasting time decoding or encoding any video data. |
-c:a libmp3lame
|
Selects the LAME MP3 encoder to transcode the MTS audio — whether it was originally AC-3 or AAC — into MP3, which is the only audio codec the J2B format supports. |
-b:a 128k
|
Sets the MP3 output bitrate to 128 kilobits per second, the default quality level for J2B output. Higher values like 192k or 320k reduce the lossy degradation introduced by transcoding from the original MTS audio codec to MP3. |
output.j2b
|
The output filename with the .j2b extension, telling FFmpeg to write the encoded MP3 audio wrapped in the J2B container structure used by Jazz Jackrabbit 2. |
Common Use Cases
- Modding Jazz Jackrabbit 2 with custom music recorded from real-world events using a Sony or Panasonic AVCHD camcorder, converting the MTS footage's audio track directly into a playable J2B game music file.
- Extracting narration or ambient sound recorded in the field on a Panasonic AG or Sony HDR series camcorder, then packaging it as J2B for use in a JJ2 level soundtrack.
- Archiving audio commentary captured during a live event on an AVCHD camcorder for repurposing within the Jazz Jackrabbit 2 community, where J2B is the native music format.
- Stripping the audio bed from MTS interview footage to create a standalone MP3-based J2B asset for game level designers who need voice or ambient tracks in their custom JJ2 episodes.
- Testing and debugging J2B playback pipelines by generating known-good J2B files from high-quality AVCHD source material with predictable bitrates.
Frequently Asked Questions
Yes — this is a lossy-to-lossy transcode. MTS camcorder audio is typically AC-3 at 192–384 kbps or AAC, and re-encoding it to MP3 via LAME introduces a second generation of lossy compression. At the default 128k bitrate the result is acceptable for game audio playback in Jazz Jackrabbit 2, but if you want to minimize quality loss you should raise the bitrate to 192k or 320k before converting.
J2B is based on the ASYLUM Music Format with a small proprietary header, and the audio data inside is MP3 encoded with libmp3lame. Jazz Jackrabbit 2 was designed for module-style ASYLUM music rather than arbitrary MP3 streams, so playback compatibility depends heavily on the specific JJ2 version or mod loader you are using. Community-patched versions of JJ2 with extended J2B support are most likely to handle MP3-based J2B files correctly.
FFmpeg first demuxes the MPEG-2 Transport Stream to extract the audio elementary stream, then fully decodes it to raw PCM audio in memory — regardless of whether it was originally AC-3 or AAC. That raw audio is then re-encoded from scratch using the LAME MP3 encoder at the specified bitrate. This means the original codec is irrelevant to the output quality; only the source's original fidelity and your chosen MP3 bitrate matter.
By default FFmpeg selects the first audio stream it finds in the MTS transport stream, which is typically the main stereo or surround mix. If your camcorder recorded a secondary audio channel — common on dual-channel professional AVCHD camcorders — you can target it explicitly by adding -map 0:a:1 to the command before the output filename to select the second audio track instead.
Replace the value after -b:a in the command. For example, change -b:a 128k to -b:a 320k for the highest MP3 quality, or -b:a 64k to produce a smaller file. J2B supports 64k, 128k, 192k, 256k, and 320k. Since this conversion already involves a lossy-to-lossy transcode from MTS camcorder audio, using at least 192k is recommended if audio fidelity matters for your use case.
Yes — on the command line you can use a shell loop to process multiple files. On Linux or macOS run: for f in *.mts; do ffmpeg -i "$f" -vn -c:a libmp3lame -b:a 128k "${f%.mts}.j2b"; done. On Windows Command Prompt use: for %f in (*.mts) do ffmpeg -i "%f" -vn -c:a libmp3lame -b:a 128k "%~nf.j2b". The browser-based tool processes one file at a time, so the desktop FFmpeg command is the practical choice for bulk conversions.
Technical Notes
MTS is an MPEG-2 Transport Stream container — the same packetized format used in broadcast television — carrying H.264 video and either AC-3 or AAC audio depending on the camcorder model and recording mode. Sony HDR and HXR series cameras commonly use AC-3, while some Panasonic AG models default to AAC. J2B originates from Jazz Jackrabbit 2 (1998) and wraps ASYLUM Music Format data; modern use of J2B with MP3 audio relies on community patches rather than the original game engine. Because both source and output formats are lossy, every conversion through this pipeline degrades audio quality — there is no lossless path from MTS to J2B. Metadata from the MTS file (camera model, recording date, GPS if present) is not carried forward into J2B since the format has no standard metadata container. The -vn flag ensures zero video decoding occurs, making the conversion fast even for long AVCHD recordings. Files over 1GB — such as extended camcorder sessions split across multiple MTS clips — are best handled using the displayed FFmpeg command locally, as the browser tool supports up to 1GB.