Convert M2TS to AAC — Free Online Tool
Extract and convert audio from M2TS Blu-ray and AVCHD files into AAC format, discarding the video stream and re-encoding the audio using AAC's efficient lossy compression. Ideal for pulling high-definition soundtrack content from Blu-ray rips or camcorder footage into a lightweight, universally compatible audio file.
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
M2TS files are MPEG-2 Transport Stream containers typically carrying HD video (H.264 or MPEG-2) alongside audio encoded in formats like Dolby AC-3, DTS, or AAC — often at high bitrates suited for Blu-ray or AVCHD playback. During this conversion, FFmpeg reads the M2TS container, discards the video stream entirely (no video re-encoding occurs), and takes the first audio stream and re-encodes it using AAC at the specified bitrate. If the source audio is already AAC, it is still re-encoded to ensure a clean, standalone AAC output file. The result is a pure audio file with no container overhead beyond what the AAC format requires, suitable for playback on virtually any modern device.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser-based version of this tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm) — no data is sent to any server. |
-i input.m2ts
|
Specifies the input M2TS file — a Blu-ray or AVCHD transport stream container that may contain HD video, one or more audio tracks, and subtitle streams. FFmpeg reads the full container and makes all streams available for processing. |
-c:a aac
|
Sets the audio codec to AAC using FFmpeg's built-in AAC encoder. This re-encodes whatever audio format is present in the M2TS (AC-3, DTS, TrueHD, or native AAC) into a standard AAC bitstream suitable for universal playback. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second, which is the default and a widely accepted balance between file size and audio quality for music and general content. For high-fidelity Blu-ray source audio, increasing this to 192k or 256k will better preserve the original dynamic range. |
output.aac
|
Defines the output file as a raw AAC audio file using ADTS framing. Because no video codec is specified and AAC is an audio-only format, FFmpeg automatically drops the video and subtitle streams from the M2TS, producing a compact audio-only file. |
Common Use Cases
- Extract the stereo or surround audio track from a Blu-ray rip to archive just the film's soundtrack as a compact AAC file
- Pull audio from AVCHD camcorder footage (which uses M2TS internally) for use in a video editing timeline or podcast without importing the full HD video
- Convert the audio commentary track from a Blu-ray M2TS recording into an AAC file for easy playback on a phone or tablet
- Reduce storage footprint of a Blu-ray movie collection by extracting audio-only versions for listening on music players or in the car
- Prepare audio from broadcast-captured M2TS recordings for upload to a streaming platform that requires AAC-encoded audio
- Strip the audio from AVCHD home video recordings to create background music or voiceover tracks for video projects
Frequently Asked Questions
It will be fully re-encoded. AAC is a completely different codec from Dolby AC-3 and DTS, so a stream copy is not possible — FFmpeg must decode the source audio and then re-encode it as AAC. This means there is a generation of quality loss, though at 128k or higher bitrates AAC typically sounds transparent for most content. If your M2TS contains a lossless audio track like Dolby TrueHD or DTS-HD MA, the quality ceiling before re-encoding is very high, so the AAC output will still sound excellent.
By default, FFmpeg selects the first audio stream it finds in the M2TS container, which is usually the primary language track. If you want to extract a specific audio track, you would need to modify the command to add a stream specifier such as '-map 0:a:1' to select the second audio track. The AAC format supports only a single audio track per file, so only one track can be extracted per conversion run.
The size reduction is dramatic. An M2TS file can easily be 20–50 GB for a full Blu-ray because it contains high-bitrate HD video alongside the audio. The resulting AAC file contains only audio at 128k by default, which works out to roughly 1 MB per minute of audio — so a two-hour film's audio track would be around 120 MB, compared to tens of gigabytes for the original. Even compared to just the audio portion of the M2TS, AAC at 128k is far more compressed than Dolby TrueHD or DTS-HD MA lossless source tracks.
Yes — AAC is one of the most universally supported audio formats available. It is natively compatible with Apple devices and iTunes, Android, modern browsers, smart TVs, car infotainment systems, and streaming platforms. Unlike the Dolby AC-3 or DTS audio often found in M2TS files, AAC requires no special licensing or decoder hardware for playback on consumer devices, making it an excellent archival and sharing format for extracted Blu-ray audio.
Metadata preservation is limited. Some basic metadata tags (such as title or language) may carry over from the M2TS stream into the AAC file, but the AAC format does not support chapters, and M2TS-specific metadata like Blu-ray disc structure information will be lost. Subtitle streams embedded in the M2TS are also discarded entirely, since AAC is a pure audio format with no container for subtitle data.
Replace the '-b:a 128k' value in the command with a higher bitrate such as '-b:a 192k', '-b:a 256k', or '-b:a 320k'. For Blu-ray source audio — especially if the original is a lossless format like Dolby TrueHD — 192k or 256k AAC will preserve noticeably more detail than the default 128k. The tradeoff is a proportionally larger output file. For spoken-word content like commentary tracks, 96k or even 64k is often sufficient.
Technical Notes
M2TS files use the BDAV MPEG-2 Transport Stream container, which multiplexes video and one or more audio streams with timing and synchronization metadata designed for the Blu-ray disc specification. Audio in M2TS files is commonly encoded as Dolby Digital (AC-3), Dolby TrueHD, DTS, DTS-HD Master Audio, or sometimes AAC for AVCHD camcorder recordings. When converting to AAC, FFmpeg must fully decode whatever source audio codec is present before re-encoding — this is a lossy transcode step regardless of the source format. The output .aac file is a raw AAC bitstream (ADTS framing), which is simple and broadly compatible but lacks the container structure of formats like M4A (which wraps AAC in an MP4 container with richer metadata support). If you need chapter markers or iTunes-style metadata, consider using .m4a as your output extension instead. Multichannel audio (5.1 or 7.1 surround) from Blu-ray sources will be down-mixed to stereo by default with FFmpeg's built-in AAC encoder; preserving surround channels in AAC would require additional mapping flags. The default FFmpeg AAC encoder ('aac') is a solid choice for this conversion; the optional 'libfdk_aac' encoder, if available in your FFmpeg build, generally offers slightly better quality at the same bitrate.