fix

main.go

@@ -735,12 +735,12 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 						return err
 					}
 
-					err = addMeta(mp4.BoxType{'\251', 'A', 'R', 'T'}, meta.Data[0].Attributes.ArtistName)
+					err = addMeta(mp4.BoxType{'\251', 'A', 'R', 'T'}, meta.Data[0].Relationships.Tracks.Data[index].Attributes.ArtistName)
 					if err != nil {
 						return err
 					}
 
-					err = addMeta(mp4.BoxType{'s', 'o', 'a', 'r'}, meta.Data[0].Attributes.ArtistName)
+					err = addMeta(mp4.BoxType{'s', 'o', 'a', 'r'}, meta.Data[0].Relationships.Tracks.Data[index].Attributes.ArtistName)
 					if err != nil {
 						return err
 					}