Your files stay on your Mac.
AVCHD MTS files hold the raw video captured by Sony and Panasonic camcorders. Converting to Apple M4A extracts the audio track and wraps it in an AAC container ready for iTunes, GarageBand, or any Apple device. The conversion runs entirely on your Mac — files never leave your machine.
Drag individual MTS clips or an entire footage folder into Convertessa. Batch mode processes every clip in one pass.
Choose Apple M4A from the output list. Adjust the quality slider to balance file size against audio fidelity.
Click Convert. Convertessa extracts and encodes the audio track locally — no upload, no waiting on a server.
Images, audio, video, documents, archives and eBooks — all converted natively, right on your Mac.
Pick a format you have — see everything Convertessa can turn it into.
Convert hundreds of files at once with per-type group defaults and individual overrides.
First-class support for HEIC, AVIF and WebP — encode and decode, both ways. Read JPEG XL and a dozen more modern formats too.
Drop files anywhere on the window. Native, instant, and exactly what you’d expect on a Mac.
Dial in compression, resolution and bitrate. Keep originals pristine or shrink for sharing.
Never overwrite a file by accident. Convertessa appends safe suffixes automatically.
Every job is logged locally. Re-run a previous conversion or revisit recent outputs in a click.
Bundle your converted files straight into a single ZIP, TAR or 7z — packaged and ready to share the moment a job finishes.
Right-click any file in Finder and choose Convert. A Quick Action handles it on the spot — no need to open the app first.
Shrink Convertessa to a tidy mini window that tucks into a corner — just a drop zone and a format picker for quick, one-off conversions.
No cloud. No account. No upload. Every conversion happens entirely on-device, using the power already in your Mac. What you convert is nobody’s business but yours.
Script conversions, wire them into your build, or batch a folder from the terminal. The same engine, no GUI required.
Read the full CLI documentation →Shrink Convertessa down to a small, focused window — drop, convert, done, with your recent conversions one click away.
macOS 14+ · Apple Silicon & Intel
New formats, new features, and fixes — every release, on the record.
Yes. Convertessa extracts the complete audio stream from the AVCHD container and re-encodes it as AAC inside an M4A file. No audio is trimmed or skipped.
Yes. Drop the folder directly into Convertessa or run convertessa ./footage/ --to m4a in the terminal to convert every MTS file in the directory in one pass.
Convertessa strips embedded EXIF and camera metadata from the audio output, giving you a clean M4A file without camcorder-specific tags.