Convert AAC to M4A
Drop a .aac file and download an .m4a carrying AAC audio at 192 kbps. Sample rate and channel count are preserved.
The point of this pair is the container. Both files hold AAC audio, but only the .m4a gives players the sample tables and metadata they need to seek, display a duration, and store tags.
This is not a remux
The audio is decoded and re-encoded rather than copied frame for frame into the new container. That costs one lossy generation. At 192 kbps the difference is minor, but it is worth knowing: a true remux would preserve the original stream bit for bit, and that is not what happens here.
When to pick MP3 instead
If the destination is old car audio or a standalone player, MP3 is the safer target. Choose .m4a when the software is current and you want the better codec plus working metadata.