There's something for which I've been searching an answer for a while now, but to no avail, and it's strange to me, as it seems like a thing that people would talk about: one of those nice little nonsense that enhance the computing experience a little bit.

Anyway. I have a fair music collection. I save all the songs as ogg files. All is fine, and I can listen to the files, but there's something weird with the files in Nautilus: some have icons displaying their album art, while others don't, and I just can't understand WHY.

I read on this site today that it's a matter of embedding the album art to the file, but that's not true, as I embedded the album art to the files I wanted several times, to no avail. Furthermore, removing an embedded album art from a file didn't have any effect on those that ARE displaying the icons.

So my question is: How does it work? Where does Nautilus (or Ubuntu, I don't know) get the picture from? How do I edit it?