Your files stay on your Mac.
AVCHD MTS is the native recording format for many Sony and Panasonic camcorders — high-quality footage in a container that most players and editors refuse to open. Convertessa decodes each MTS clip on your Mac and re-encodes it to MP4, preserving the original resolution and frame rate. No uploads, no cloud processing — your footage never leaves the machine.
Drag individual MTS clips or an entire AVCHD folder into Convertessa. Every clip in the folder is queued for conversion in a single pass.
Choose MP4 from the output format list. Because MP4 uses lossy compression, you can set quality to balance visual fidelity against file size before converting.
Click Convert. Convertessa re-encodes each clip locally and saves the MP4 files alongside the originals. Nothing is sent to 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 runs entirely offline. No footage is uploaded to any server — every transcode happens locally on your Mac from start to finish.
Yes. MP4 uses lossy compression, so Convertessa lets you set quality before you convert. A higher quality setting preserves more detail and produces a larger file; a lower setting reduces file size at the cost of some fidelity.
Yes. Drop the AVCHD folder onto Convertessa or run convertessa /path/to/clips/ --to mp4 in the terminal — every MTS clip inside is converted in one pass without touching each file individually.