Extract Audio from MTS to M4B — Free Online Tool
Extract audio from MTS camcorder footage and save it as an M4B audiobook or podcast file with AAC encoding. This tool strips the H.264 video stream from AVCHD recordings and packages the AC-3 or AAC audio into an MPEG-4 container with chapter and bookmarking support — ideal for repurposing interview footage, lectures, or event recordings into structured audio content.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your MTS 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
MTS files from Sony and Panasonic camcorders use the MPEG-2 Transport Stream container, typically carrying H.264 video alongside AC-3 or AAC audio. This tool discards the video stream entirely and transcodes the audio to AAC at 128k bitrate, then wraps it in the MPEG-4 container format that M4B uses. Because M4B is purpose-built for audiobooks and podcasts, the output container natively supports chapters and bookmarking — features absent in the raw MTS source. The -movflags +faststart flag reorganizes the file metadata to the front of the output, which is important for streaming and podcast delivery. If the source audio was already AAC, transcoding introduces a small additional generation loss; if it was AC-3 (Dolby Digital, common on higher-end AVCHD cameras), it is fully re-encoded to AAC.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary. In the browser, this runs via FFmpeg.wasm (WebAssembly), so no installation is needed and no files leave your device. |
-i input.mts
|
Specifies the input AVCHD MTS file from your Sony or Panasonic camcorder. FFmpeg reads both the H.264 video stream and the AC-3 or AAC audio stream from the MPEG-2 Transport Stream container. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the H.264 video stream in the MTS file. This is the core of the audio extraction — only the audio track is passed to the output. |
-c:a aac
|
Encodes the audio using FFmpeg's native AAC encoder, which is the required codec for M4B files. Whether the source MTS audio was AC-3 or AAC, it is transcoded to AAC to ensure compatibility with Apple devices, podcast players, and audiobook apps. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is appropriate for speech-heavy content like lectures, interviews, or tours extracted from camcorder footage, providing a good balance of file size and clarity. |
-movflags +faststart
|
Relocates the MP4/M4B metadata (moov atom) to the beginning of the output file. This is required for podcast delivery and streaming because it allows podcast clients and audiobook apps to start playing the M4B before the full file has downloaded. |
output.m4b
|
The output filename with the .m4b extension. The M4B extension signals to Apple devices, podcast apps, and audiobook players that this file supports bookmarking and chapters, enabling the resume-playback behavior that distinguishes M4B from a plain .m4a or .aac file. |
Common Use Cases
- Convert a recorded lecture or conference talk from a camcorder into an M4B podcast episode with bookmarking so listeners can resume where they left off
- Extract the audio from a recorded interview or documentary shoot to produce an audiobook-style episode without needing a dedicated DAW
- Repurpose MTS footage of a guided tour, meditation session, or instructional workshop into a structured M4B file that supports chapter markers for easy navigation
- Archive spoken-word camcorder recordings — such as field notes, oral histories, or training videos — into a compact, podcast-compatible audio format
- Strip audio from AVCHD event recordings (weddings, ceremonies, speeches) to create a standalone M4B keepsake that can be bookmarked on any Apple or podcast-compatible device
- Prepare audio from MTS news or broadcast footage for distribution via podcast platforms that prefer the M4B container for enhanced listener experience
Frequently Asked Questions
It depends on the original audio codec in the MTS file. AVCHD camcorders record audio as either AAC or AC-3 (Dolby Digital). In both cases, the audio is re-encoded to AAC at 128k — so yes, there is a small degree of transcoding loss. If the source was AC-3 (a lossy format), you are performing a lossy-to-lossy transcode. If it was already AAC, you are decoding and re-encoding, which adds a generation of compression. At 128k AAC the result is generally transparent for speech content, but if you are archiving music or high-fidelity audio from your camcorder, consider increasing the bitrate to 192k or 256k.
The M4B container supports chapters natively, but this tool extracts audio from MTS without adding chapter markers automatically — MTS transport streams do not embed chapter data that can be directly mapped to M4B chapters. To add chapters to the output M4B file, you would need a second step using a tool like mp4chaps or an audiobook editor after conversion. The resulting M4B file is fully chapter-capable, however, so adding them post-conversion is straightforward.
M4B is specifically designed for audiobooks and long-form audio content because it supports bookmarking (the playback position is remembered when you pause or switch apps), chapter navigation, and rich ID3-style metadata — all inside an MPEG-4 container. For repurposing camcorder recordings of lectures, tours, or interviews, M4B is far more useful than a plain MP3 because listeners on Apple Podcasts, Apple Books, or any podcast app can bookmark their place and jump between sections. If you only need a flat audio file, MP3 or M4A would be simpler alternatives.
Replace the value after -b:a in the command. For example, to encode at 192k instead of 128k, change the command to: ffmpeg -i input.mts -vn -c:a aac -b:a 192k -movflags +faststart output.m4b. For voice-only content like interviews or lectures, 128k AAC is typically indistinguishable from higher bitrates, but if your MTS footage contains music or ambient sound you want to preserve accurately, 192k or 256k is a reasonable choice. Going above 256k with AAC yields diminishing returns in perceptible quality.
Yes, on a desktop you can run the FFmpeg command in a shell loop. On Linux or macOS: for f in *.mts; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k -movflags +faststart "${f%.mts}.m4b"; done. On Windows PowerShell: Get-ChildItem *.mts | ForEach-Object { ffmpeg -i $_.Name -vn -c:a aac -b:a 128k -movflags +faststart ($_.BaseName + '.m4b') }. The in-browser tool processes one file at a time, so the FFmpeg command is especially useful when you have a folder of MTS recordings from a shooting session.
AVCHD MTS files can carry multiple audio tracks — for example, a stereo mix and a second-channel audio track recorded on a dual-channel camcorder. By default, FFmpeg selects the best audio stream (usually the first stereo track) and maps it to the M4B output, since M4B does not support multiple audio tracks. If your MTS file has a secondary audio channel you specifically want to extract, you can add -map 0:a:1 to the command to select the second audio stream instead of the default.
Technical Notes
MTS is the file extension for the AVCHD standard, which wraps H.264 video and either AC-3 (Dolby Digital, typically at 192–256 kbps) or AAC audio inside an MPEG-2 Transport Stream. The transport stream format adds packetization and error-correction overhead that is stripped during demuxing, so the output M4B will be noticeably smaller than the source MTS — not just because video is removed, but because the container overhead is eliminated. The -movflags +faststart flag is essential for M4B files intended for podcast or streaming delivery: it moves the moov atom to the beginning of the file so players can begin playback before the entire file is downloaded. Without it, some podcast clients or streaming services may fail to play the file until it is fully buffered. AAC encoded with FFmpeg's native AAC encoder (used here) is broadly compatible with Apple devices, Android, and all major podcast platforms. Note that M4B files processed by this tool will not automatically inherit metadata tags (title, author, description) from the MTS source — those fields should be populated using a tagging tool like Mp3tag or mutagen after conversion if you intend to distribute the file via a podcast feed.