Vorbis comments repeat a field to give it several values (GENRE=Boom Bap, GENRE=Downtempo, ...). dhowden/tag keeps comments in a map keyed by field name, so each repeat overwrote the previous one and only the last genre was stored. MP4 has the same gap: several data atoms in one ©gen atom, or repeated ©gen atoms, collapse to one value. On the operator's library 3,658 of 4,092 FLACs declare more than one genre. Kupla's Life Forms carries eight and was stored as "Instrumental Hip Hop" alone, so browse and the taste profile never saw the other seven. - vorbisgenre.go reads the comment block directly: FLAC's metadata block (including FLACs behind an ID3v2 tag), and the comment packet of Ogg Vorbis and Opus, reassembled across pages when cover art makes it span several. - mp4genre.go walks moov > udta > meta > ilst and returns every ©gen text value. It handles ISO and QuickTime meta layouts and a moov placed after mdat. A file with only the numeric gnre atom still falls back to dhowden, which resolves it. - extractGenres routes VORBIS and MP4 through them, as #2499 did for ID3v2. - tagReadVersion 3 -> 4, so the next scan re-reads the tags of files already indexed. Unchanged files keep their duration and fingerprint, so the pass costs tag reads only. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
