Your files stay on your Mac.
AVCHD MTS files wrap high-definition video together with one or more audio tracks. Converting to FLAC extracts those tracks in lossless quality, giving you a bit-perfect audio archive. Everything runs locally on your Mac — no file ever leaves your machine.
Drag one MTS clip or an entire AVCHD footage folder into Convertessa. The app finds every MTS file in the hierarchy and queues them for conversion.
Pick FLAC from the output format list. Because FLAC is lossless, the audio extracted from your MTS files is preserved bit-for-bit with no quality loss.
Click Convert. Convertessa processes each file locally — nothing is uploaded. Your FLAC files appear alongside the originals when the batch finishes.
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. FLAC is a lossless format, so every sample from the original MTS audio track is preserved exactly. The resulting file is bit-for-bit identical in audio content to the source.
Yes. Drop the top-level folder from your card or camera into Convertessa and it will locate every MTS file inside, including those nested in AVCHD subfolders, and convert them all to FLAC in one pass.
Yes. Convertessa strips embedded metadata during conversion, so your output FLAC files contain only the audio data — no camera identifiers or location tags carry over.