Started doing some learning because of satellite and HD radio and felt like asking about it here because a lot of Hydrogen Audio threads kept showing up in my searches.

If I have this right, EPAC > mpeg-4 AAC > mpeg-2 AAC > PAC? But I think there's some debate out the relative position of the last 2. I don't know where Ogg Vorbis is supposed to fit into that, but I did find an internet radio station that broadcast in 80 kbps Ogg that I thought sounded a lot better than one in 80 kbps AAC+. The high frequencies in 80 kbps AAC+ sounded very rough to me.

And will EPAC ever see the light of day? The world already has so much hardware invested in earlier codecs that I think it is too late for it to do any good. Maybe if HD radio and satellite radio fail a successor service can take advantage of EPAC.

Most people probably already figured this out - but ePAC is a very old codec. I must have stumbled on an extremely old thread via google. They stopped making a distinction with the names a long time ago, apprently. Thus my confusion. The value of the ePAC codec is very dubious, it was chosen as much to avoid the mpeg licensing fees as for the sound quality.