Your files stay on your Mac.
Converting AVCHD MTS to AC-3 pulls the Dolby Digital audio track out of your camcorder footage and saves it as a standalone .ac3 file. Convertessa runs entirely on your Mac — no files are uploaded, no internet connection required. Batch-convert a whole folder of clips at once and set output quality to match your project needs.
Drag a single .mts clip or an entire folder of AVCHD footage onto Convertessa. All files are processed locally on your Mac.
Choose AC-3 from the output list. Because AC-3 is a lossy format, you can also set the output quality before converting.
Click Convert. Convertessa extracts the audio track from each clip and writes .ac3 files alongside your originals — nothing leaves your Mac.
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.
No. Convertessa runs entirely offline on your Mac. Your AVCHD footage never leaves your machine — there is no upload, no cloud processing, and no account required.
Yes. Drop an entire folder onto Convertessa and it will extract AC-3 audio from every MTS file inside. From the command line, pass the folder path: convertessa /path/to/folder --to ac3.
Yes. AC-3 is a lossy format, so Convertessa lets you set the output quality before converting. Pick the level that fits your project — higher quality means a larger file.