I read your entry on Macintouch, and I’d like to ask your ‘lab’ opinion on high-end audio cables. The best reason I can see for them is the sheilding to remove hum and other unmentionables from the signal. but is it true that their expensive wrapes and metals make better signal carrying?

thx

Check out http://www.xciv.org/~meta/audio-shootout/

I remember when studying digital signal processing, and specifically quantisation and encoding, that the design of such systems was all about trade-offs and context — what type of signal is to be encoded? Depending on the type (which therefore establishes a number of assumptions about the signal), we could perhaps encode the difference between samples, and not their absolute magnitude. Such encoding fails completely when the underlying assumptions of the signal source no longer hold.

Clearly the AAC sample you provide contains audible artifacts that are not present in the MP3 or OGG samples. However, the content of your music sample doesn’t come from natural sound sources, like voices or musical instruments. I wonder if your experiment is really “fair”, or representative, or whether it’s like saying, “If you really think JPEG is better than GIF, just have a look at this JPEG compressed computer-generated image of a white typeface set on a black background.” JPEG won’t handle those infinite frequency transitions too well, but then again, it wasn’t design to.

As I believe I say on my web page, if you listen to a lot of orchestral music or indie guitar pop, the results you get might be entirely different, so you need to test the encoders with your music. For the music I listen to, AAC is terrible compared to MP3 (as encoded by LAME).

I wonder how much of it is AAC’s algorithms, and how much is the encoder, given how bad Apple’s MP3 is compared to LAME MP3. There’s an open source AAC encoder I’d like to try at some point, but it’s a pain to build so I haven’t gotten around to it.