MyMediaTools

Convert M2TS to M4A — Free Online Tool

Extract audio from Blu-ray and AVCHD M2TS files and save it as M4A, encoding the audio stream to AAC at 128k bitrate while stripping all video data. Ideal for pulling high-quality audio from Blu-ray rips or camcorder footage into a compact, iTunes-compatible format.

FFmpeg Command

Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg

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Estimated output:

Conversion Complete!

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How It Works

M2TS is a transport stream container designed for Blu-ray and AVCHD, often carrying video (H.264 or VC-1) alongside audio encoded in formats like Dolby TrueHD, DTS-HD, AC-3, or AAC. M4A is an audio-only MPEG-4 container that cannot carry video. During this conversion, the video stream is completely discarded using the -vn flag. The audio track is then decoded from whatever codec it was originally encoded in and re-encoded to AAC at 128k bitrate, then wrapped in the M4A container. This means the conversion always involves audio transcoding — even if the source already contains AAC, it is decoded and re-encoded to ensure compatibility with the M4A container and target bitrate. The result is a compact audio file playable in iTunes, Apple Music, iOS, and most modern media players.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg program, the open-source multimedia processing engine that powers this conversion both in the browser via WebAssembly and on the desktop via a local installation.
-i input.m2ts Specifies the input file — in this case an M2TS transport stream, which may have originated from a Blu-ray disc rip or an AVCHD camcorder. FFmpeg will automatically detect all contained streams including video, audio, and subtitles.
-c:a aac Sets the audio codec to AAC (Advanced Audio Coding) using FFmpeg's built-in native AAC encoder. This is required because M4A is an AAC-centric container, and whatever audio codec the M2TS source contains — TrueHD, DTS, AC-3, or PCM — must be transcoded to AAC.
-b:a 128k Sets the AAC audio bitrate to 128 kilobits per second, which is the standard quality level for general-purpose listening. For Blu-ray source material with lossless audio, increasing this to 256k or 320k will better preserve the fidelity of the original track.
-vn Disables video output entirely, which is essential for this conversion because M4A is an audio-only container and cannot store a video stream. Without this flag, FFmpeg would attempt to include the video from the M2TS file and either error out or produce an incompatible file.
output.m4a Defines the output filename and format. The .m4a extension tells FFmpeg to wrap the encoded AAC audio in an MPEG-4 audio container, which is natively supported by iTunes, Apple Music, iOS, and most modern media players.

Common Use Cases

  • Extract a concert or live performance soundtrack from a Blu-ray disc rip to listen to on an iPhone or iPod without carrying the full video file
  • Pull the audio commentary track from an AVCHD camcorder recording to use as a narration or reference file in a video editing project
  • Convert the audio from a Blu-ray film rip into M4A for use as background music in a playlist, removing the large video component
  • Extract dialogue or ambient audio from a high-definition M2TS broadcast recording for use in audio post-production or transcription
  • Archive the audio portion of home videos shot with an AVCHD camcorder in a widely compatible format before deleting the bulky originals
  • Strip the music track from a professionally recorded Blu-ray concert for use in Apple Music library or podcast editing software

Frequently Asked Questions

Yes, some quality loss is expected in most cases. Blu-ray M2TS files frequently carry lossless or high-bitrate audio formats like Dolby TrueHD, DTS-HD Master Audio, or AC-3, all of which must be decoded and re-encoded to AAC for the M4A container. This decode-then-re-encode process is called transcoding and always introduces some generational loss. At 128k AAC the result is generally transparent for casual listening, but if the source is lossless and you need to preserve maximum fidelity, consider increasing the bitrate to 256k or 320k in the FFmpeg command.
By default, FFmpeg selects the first audio track it identifies in the M2TS file, which is typically the primary audio stream. M4A does not support multiple audio tracks, so only one track will appear in the output. If you want to extract a specific track — for example, the commentary — you can add the flag '-map 0:a:1' to the FFmpeg command to target the second audio stream (index 1) instead of the default.
M4A supports chapter markers natively, but M2TS chapters are not structured in a way that FFmpeg reliably maps across during this conversion, so chapters are typically lost. Basic metadata such as title or language tags embedded in the M2TS stream may partially transfer, but Blu-ray-specific metadata and disc-level information will not survive the conversion. If chapter markers matter for your workflow, consider adding them manually using a tool like MP4Box or iTunes after the conversion.
The audio bitrate is controlled by the '-b:a 128k' flag in the command. You can replace '128k' with any supported value such as '64k', '96k', '192k', '256k', or '320k' depending on your needs. For extracting audio from a lossless Blu-ray source where you want near-transparent quality, '256k' or '320k' AAC is a practical upper bound. Raising the bitrate above 320k provides no meaningful benefit for AAC.
The displayed command processes one file at a time, but you can batch process on your desktop using a shell loop. On Linux or macOS, run: for f in *.m2ts; do ffmpeg -i "$f" -c:a aac -b:a 128k -vn "${f%.m2ts}.m4a"; done. On Windows Command Prompt, use: for %f in (*.m2ts) do ffmpeg -i "%f" -c:a aac -b:a 128k -vn "%~nf.m4a". The browser-based tool processes files individually, so the FFmpeg command is especially useful for batch jobs involving many large M2TS files.
Yes. M4A with AAC audio is the native audio format used by Apple's ecosystem. Files produced by this conversion will import cleanly into iTunes and Apple Music, play on iPhone and iPad without conversion, and are recognized by AirPlay and HomePod. The AAC codec at 128k or higher is also the format Apple uses for its own music store, making this output essentially purpose-built for Apple compatibility.

Technical Notes

M2TS files from Blu-ray sources can carry a wide variety of audio codecs including Dolby TrueHD, Dolby Digital (AC-3), DTS-HD Master Audio, DTS, PCM, and AAC — all of which FFmpeg can decode but must transcode to AAC for M4A output. The -vn flag is mandatory here because M4A is a video-free container and attempting to include a video stream would cause FFmpeg to error or produce an unplayable file. AVCHD camcorder M2TS files typically use Dolby Digital or PCM audio, which will also be fully transcoded. One known limitation is that M2TS transport streams occasionally have timestamp discontinuities that can cause sync issues or FFmpeg warnings during processing; if you encounter audio drift in the output, prepend '-fflags +genpts' to the command to have FFmpeg regenerate timestamps. The M4A container uses the MPEG-4 Part 14 structure and supports iTunes-style metadata atoms (artist, album, track title), but these must be written separately with a tagging tool since M2TS does not carry equivalent metadata fields. Files produced in the browser are limited to 1GB input; for full Blu-ray rips that exceed this, use the displayed FFmpeg command locally on your desktop where no file size restriction applies.

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