It seems like the brasero ebuild should have a flac USE flag which depends on gst-plugins-good and gst-plugins-flac.
I should also mention that FLAC files aren't supported in brasero without gst-plugins-good and gst-plugins-flac.
Why also gst-plugins-good?
I'm adding a blurb to pkg_postinst about gstreamer installation needing to support the files you want to burn, but a useflag won't be possible, since this is strictly a runtime dependency.
I do think that it would be interesting to have a list of gstreamer plugins and the formats they support though.
The list is provided by 'emerge -pv gst-plugins-meta' at the moment, with the current gst plugins split there's nothing us (media-optical) can do to fix this situation as USE depending on meta pkg would be... ridicilous.
I strongly suggest moving back to -good, -bad, -base, -ugly, ...
Moving to gstreamer@
Only a question, does brasero give you any error messages when trying to handle flac files without needed gst-plugins or does it fail silently?
this actually would be a duplicate of bug #241674
*** This bug has been marked as a duplicate of bug 241674 ***