audacious-plugins-1.3.0_alpha2 supports TTA. This feature is dependence on libid3tag but this dependence is not described in current ebuild file. Reproducible: Always Steps to Reproduce:
Created attachment 107979 [details, diff] patch to add dependence and new USE flag.
The tta local USE-flag has been added to the alpha3 ebuild. Thank you for your bug report :)