In his story You Can’t Be Too Thin for Slate, Paul Boutin describes aacPlus (AAC+SBR) as a potential successor to MP3 for low-bitrate audio. A proprietary variation of standard AAC (without SBR) is used in iPods and iTunes and is somewhat better than MP3 for some applications. AAC is also used by some radio stations and IT Conversations for studio-to-studio links over ISDN lines. Another variation, AAC-LD (for low-delay) is great for audio over POTS lines. The popular presentation at Pop!Tech 2004 by Malcolm Gladwell was streamed from Maine to IT Conversations this way, then re-encoded into MP3 for downloading. aacPlus does indeed sound good at 48kbps and remarkably good at 64kbps. (The 18-month-old reporty cited by Paul wasn’t able to test 64kbps at that time.)
But for the hard-core audio geeks out there, a few clarifications: The basic AAC and MP3 algorithms are in the same family known as perceptual codecs. The “plus” is Spectral Band Replication which is also available with MP3s as MP3Pro. Also, Paul describes aacPlus’ handling of stereo as L+R and L-R signals. This isn’t all that new, since most modern codecs use this scheme and some go even further. (The EBU’s test document doesn’t say which stereo scheme was used for their tests.)
Paul writes that “Webcasters spend most of their money paying for network traffic,” and refers to a $4,000 monthly bill to support 1,000 listeners. I did that math, and he’s in the ballpark. If those listeners were tuned into a 64kbps stream 24 hours a day for the entire month, the cost would indeed be between $5,000 and $8,000 each month and somewhat less at 48kbps. Of course, with BitTorrent the costs drop dramatically, but BT only helps with downloads, not streams. There are, however, P2P technologies for streaming and others are on the way.
But is Paul correct that “Future digital music players will support the format just as surely as they do MP3?” I’m not as optimistic. Sony, for example, is just now coming around to supporting MP3, and Apple has a lot invested in its proprietary version of standard AAC. My sense is that it will take a long time. Don’t hold your breath.