Your files stay on your Mac.
AC-3, also known as Dolby Digital, is the surround-sound codec required by DVD-Video, widely used on Blu-ray, and standard for digital broadcast television. Converting your AAC files to AC-3 produces audio that home-theatre receivers, video-authoring tools, and broadcast encoding pipelines can decode natively. Convertessa performs the entire re-encode on your Mac — no files are uploaded.
Drag one .aac file or an entire folder into Convertessa. The app queues every AAC file it finds, so you can process a whole album or episode batch in one pass.
Choose AC-3 from the output format list. Use the quality slider to balance fidelity and file size — raise it to preserve more of the original audio, or lower it for smaller output files.
Click Convert. Convertessa processes every file locally without an internet connection. Output files land beside the originals, renamed with the .ac3 extension.
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.
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AC-3 (Dolby Digital) is a multi-channel audio codec developed by Dolby Laboratories. It is the mandatory audio format for DVD-Video, is widely supported on Blu-ray, and is the broadcast standard for digital television in North America. Home-theatre receivers and set-top boxes decode AC-3 natively without additional software.
Both AAC and AC-3 are lossy codecs, so a re-encode introduces a small amount of generation loss. Use the quality slider in Convertessa to set the AC-3 encode level that best fits your fidelity and file-size requirements.
Yes. Drop a folder onto Convertessa and it will find every AAC file inside, including subfolders. From the terminal, run convertessa ./folder --to ac3 to batch-convert from the command line.