99% of my music libraries use the aac codec, although there was a time when mp3 was popular it offered very poor quality. So at a minimum I encoded using aac.
However, after searching for xmms-mp4 plugin for XMMS, I found these plugins from tc-4.x were never copied to tc-5, tc-6.x or tc-7.x (perhaps because of deps?)
"xmms-mp4 plugin" extension verified works in tc-7.2 (with faad.tcz as listed in xmms.tcz.dep is installed)
Strange thing is faad.tcz info file "Title" or the extension itself needs updating as it's Title is listed as faad2.tcz while extension is named faad.tcz. It's likely the extension contains faad2 as this version appears the only version available AFAIK.
So I have to assume these remaining plugins work in all newer tc versions also
xmms-flac.tcz (requires flac.tcz dep, already in tc-7 repo)
xmms-wma.tcz (does not require any deps afaik)