How to convert AU to FLAC
- Add your .AU file - drop it in the box above or click to browse.
- Convert it to .FLAC in a few seconds.
- Download your new .FLAC file.
What to expect
- FLAC is lossless - the output quality exactly matches the source; if the AU file is 8-bit mu-law at 8 kHz (classic telephone quality), the FLAC will be equally limited.
- ffmpeg decodes 8-bit mu-law AU to 16-bit PCM before writing FLAC; this is normal and correct, since mu-law uses 14 bits of dynamic range and no information is lost.
- AU carries only a minimal optional annotation field; you can add proper FLAC tags (artist, title, album) during export in Audacity or WavePad.
Frequently asked questions
Does converting AU to FLAC lose quality?
No - both formats are lossless, so the conversion is a clean decode-and-re-encode with no quality loss relative to the source.
My AU file sounds poor even after converting to FLAC - why?
Classic AU files are often 8-bit mu-law at 8 kHz (telephone quality). The FLAC faithfully copies that limited source; it cannot recover detail that was never recorded.
Can I batch-convert multiple AU files at once?
Yes - ffmpeg handles batch conversion with a single shell loop. Audacity can also batch-export using its Macro feature (Edit > Macros).
Will the FLAC file be smaller than the AU file?
Usually yes - FLAC compression typically reduces file size by 40-60% compared to uncompressed PCM, though the exact saving depends on the audio content.
