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Anyways, here's listening tests at 64kbps. HE AAC beats Vorbis handily, QT AAC not so well... but that's at 64 kbps. 128kbps tests are here.

There's more here and here.

Overall, Vorbis seems to be great at low bitrates - 64 kbps, for instance. At higher bitrates, though, it doesn't keep up compared to AAC.

-T

Anyways, here's listening tests at 64kbps. HE AAC beats Vorbis handily, QT AAC not so well... but that's at 64 kbps. 128kbps tests are here.

There's more here and here.

Overall, Vorbis seems to be great at low bitrates - 64 kbps, for instance. At higher bitrates, though, it doesn't keep up compared to AAC.

-T

The MP3/AAC licensing costs are miniscule compared to the cost of the rest of the components. It's probably in the range of 50c - $1 per device, or less.The cost of the RAM/HD is 100x any licensing costs.

The file transfers would be disgustingly slow because of the overhead required to transcode every file to the machine. And it would need proprietary software to put music on it (to do the transcoding) which is one of the few complaints people have about the iPod.

Vorbis is nice, but it is inferior, sound quality wise to WMA Pro, AAC, and MusePack, and it's never going to be popular (in a marketshare sense). I know it hurts to hear it, but it's true.

All things being equal (source quality, etc.), which they probably aren't, AAC should beat out WMA handily at bitrates like what the iTMS and Wal-Mart are using. The only chance WMA would have of approaching AAC in quality at that bitrate would have been if Wal-Mart had used WMA Pro, but because of the lack of hardware player support for WMA Pro, that probably won't happen soon.

I haven't seen tests directly comparing AAC to WMA (non-Pro), but Roberto Amorim's testing at 128kbps with AAC and WMA Pro and ff123's testing of a different AAC codec against WMA non-Pro probably say enough.

Also, Apple has actually spoken about the quality of the sources that they encode from (the original masters rather than CDs themselves), and Wal-Mart hasn't.

I do hope that whoever elects to actually directly compare the quality of Wal-Mart's music to Apple's doesn't just look at frequency analysis to do it. Apple's AAC lowpasses at 16 KHz, but to use this as some sort of indication of quality is ludicrous.

Ok, first of all, while the test was DISCUSSED on HydrogenAudio, and most of the participants are HA regulars, Roberto Amorim did all the hard work of organizing the test and compiling the results, dealing with complaints, etc. To not give him credit is not very nice.

Second, there was a 128kbps test a month or two ago (which for some reason got repeatedly rejected when submitted to slashdot). You can see it here. Unfortunately, the results there aren't quite as interesting (it was mostly a big tie). Unfortunately, tests at higher bitrates are difficult because detecting problems at, say, 160kbps often requires well trained ears and good audio equipment.

Third, it's a good idea when commenting on an article to actually read it and click around on a few links to actually have an idea what you are talking about. Many /.ers seem to be only half-literate (can write but not read). There is a hilarious number of denegrating comments here by people who know nothing about either statistics or psychoacoustic audio compression. ABC/HR type methodology is the standard for comparing the relative quality of audio sources. Also, a great deal of effort went in to assuring that the best settings for the best encoders for each codec were used for the test. A little reading of the pre-test discussions would reveal this. Further, HydrogenAudio is not a club of audiofools who spend zillions of dollars on fancy speaker cable without any science to back it up. It is an objectivist forum. Anyone who makes statements without backing them up (with something like ABC/HR or ABX results) gets flamed HARSHLY. Some of the regluars have PhDs on various audio topics. They know what the fuck they're doing.

Fourth, just because you don't have a use for 64k audio, doesn't mean the results are meaningless. Lots of people have small-capacity players, and some codecs can tolerate that bitrate for very casual listening (such as in the car). Lots of streaming audio sources are at this bitrate or lower. Satellite radio is at 64k or lower. Also, it's not a good idea to try to extend these results to other bitrates. MPC for example, isn't even worth considering at 64kbps, but at bitrates over about 140kbps, it will beat the pants off of anything else.

Finally, for those who want to know more, or want their audio collections to sound best, read the FAQs at HA. Many codecs have a preset where they are transparent for the vast majority of samples; usually a VBR setting that averages somewhere between 160 and 200kbps (such as lame --preset standard, mppenc --standard, oggenc around -q5 or -q6).