Currently, Flacon only supports faac. This is a shame since it's a really shitty implementation of the .m4a music format.

details:

• https://listening-test.coresv.net/results.htm
• http://wiki.hydrogenaud.io/index.php?title=AAC_encoders
• http://soundexpert.org/articles/-/blogs/opus-aac-vorbis-mp3-mpc-at-128-kbit-s

I would therefore ask you to change the supported aac encoder from faac do fdk-aac. See also the details on the listening test listed above.

I already use it for ripping CD's in Asunder and it provides significant quality improvements. You could optionally support both, but I would recommend you to always pick fdk-aac if available.

Here the Asunder manifest that uses fdk-aac instead of faac:
https://github.com/flathub/ca.littlesvr.asunder/blob/master/ca.littlesvr.asunder.yaml