Add your MTS file
Drop one or more .mts files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
MTS to M4A
Pulling the soundtrack out of a .mts video into .m4a audio keeps what you can hear and drops the picture entirely. Free, private, and validated — the file never leaves your browser.
100% private for supported formats
Runs on your deviceConvert supported files
Drop MTS files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting AVCHD video to MPEG-4 audio
Pulling the soundtrack out of a .mts video into .m4a audio keeps what you can hear and drops the picture entirely. An .mts file is AVCHD footage as written to a camcorder's memory card, containing H.264 video inside an MPEG transport stream. Sony and Panasonic camcorders from the late 2000s onward filled SD cards with .mts clips, so the extension is familiar to anyone importing family or event video.
An .m4a file is an MPEG-4 container that holds only audio, most often AAC and occasionally Apple Lossless. Apple coined the .m4a extension so audio would not be confused with .mp4 video, and it remains the default for iTunes purchases, Apple Music downloads, and Voice Memos. For this route the practical draw is real tagging and artwork support, unlike bare .aac streams and gapless playback metadata for continuous albums — balanced against the extension hides whether the contents are lossy or lossless, muddying quality expectations, which is worth knowing before you commit a large batch.
Why convert MTS to M4A?
The usual reason to take .m4a audio out of a .mts file is that only the sound matters — a talk, interview, song, or podcast segment. Keeping the video stream would waste storage, and a dedicated audio file is easier to trim, tag, and play. On the source side, transport-stream packet overhead makes files larger than the same video in MP4; on the target side, the payoff is real tagging and artwork support, unlike bare .aac streams, which is exactly what you want for managing music inside iTunes and Apple Music libraries.
MTS vs M4A at a glance
| Aspect | AVCHD video (.mts) | MPEG-4 audio (.m4a) |
|---|---|---|
| Format type | Container — quality depends on the codecs and settings inside | Lossy — discards detail it judges invisible to shrink files |
| How it stores data | uses 192-byte transport packets, standard 188-byte packets plus a 4-byte arrival timestamp, matching Blu-ray's BDAV layout | an ISO base media container restricted to audio tracks, structurally a sibling of MP4 |
| Strongest at | importing camcorder footage into Premiere, Resolve, or Final Cut | managing music inside iTunes and Apple Music libraries |
| Weak spot | transport-stream packet overhead makes files larger than the same video in MP4 | the extension hides whether the contents are lossy or lossless, muddying quality expectations |
| Metadata | recording date, camera settings, and GPS coordinates on some models are stored in the AVCHD folder's clip-info files rather than in the .mts stream itself | iTunes-style metadata atoms: title, album, artwork, composer, BPM, and the iTunSMPB gapless-playback data |
Pick M4A as the output
Select .m4a in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if M4A is selectable, the route is real and validated.
Convert on your device
Press Convert. A WebAssembly FFmpeg build demuxes the audio track and re-encodes it locally; the video stream is simply discarded.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid M4A file. Outputs keep the original filename with the .m4a extension.
MTS to M4A questions, answered
Will converting MTS to M4A lose quality?
Since mts is container-oriented and m4a is lossy-oriented, the conversion preserves the source content exactly as stored; no additional compression pass is applied beyond what .m4a itself requires.
Is it private to convert MTS files here?
Yes — the .mts file is processed inside your browser tab and never uploaded. A WebAssembly FFmpeg build demuxes the audio track and re-encodes it locally; the video stream is simply discarded. Close the tab and the file is gone from memory.
Where will the M4A file work?
Browsers, Windows, Android, and every Apple device play AAC-based .m4a files without extra software. The ALAC-filled variety is slightly narrower, since some inexpensive devices decode only the AAC form.
Will the M4A file be bigger or smaller than my MTS?
Much smaller — the video stream is usually 80–95% of a .mts file's weight, and it is discarded entirely. The remaining audio is re-encoded at the bitrate implied by your quality setting.
What happens to the metadata in my MTS file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, recording date, camera settings, and GPS coordinates on some models are stored in the AVCHD folder's clip-info files rather than in the .mts stream itself; none of it is transmitted anywhere because the file never leaves your browser.