Crossposted from https://lemmy.world/post/25939068
256kbps AAC is still proprietary, but you can convert it to an MP3 with something like dBPowerAmp
Advanced Audio Coding (AAC) is patented and requires a license for legal use.
I mean so is MP3. If you really want to be a non-proprietary purist you need to rely on Opus for a lossy audio compression, which is not as widely supported in music players as MP3 or AAC.