I stumbled upon the following while looking for discussion on the iPod photo on technorati:

Most agree Apple passed on crushing online music competition and devastating WMA by not announcing/implementing AAC Plus, but there is reason we did not see AAC Plus today…


What is this AAC Plus of which he speaks? Why didn’t Apple deploy it to forcefully crush all comers?

Um, maybe because its pretty irrelevant on the iPod. Following the links in the post, I learn that AAC Plus improves compression by about 30% over standard AAC at the same quality level. That’s pretty cool, but then I considered that I’m already having trouble filling my old 10GB iPod — i’m not sure more efficient encoding is that important to me, and from Apple’s point of view, they are already running into challenges about how to motivate people to upgrade as the storage capacity on iPods starts to outstrip more and more People’s music collections. Besides, I’d guess that the people with the largest collections have downloaded most of it, and those downloads are already compressed in MP3 format, so reencoding is going to be completely undesirable.

More importantly, looking at the quality graphs, it looks like the perceived quality of AAC Plus vs Regular AAC probably convergest somewhere between 48kbps and the 128kbps default used by iTunes, so its not even clear there would be any clear advantage over AAC either space or quality-wise in the domain most iPod users exist.

AAC Plus seems to be targeted at the mobile wireless music market, where bit-efficiency is important from a bandwidth rather than a storage perspective. The iPod doesn’t connect to cellular networks, end of story.

The mystery is, why make a big deal about the lact of AAC Plus support in the new iPod? And why am I even bothering to ask that question?