Here are some more tests:
http://src.infinitewave.ca/
This one doesn't have anything with the core audio SRC, but it does
have the Weiss SRC, which is supposed to be the best.
http://www.bias-inc.com/products/peakPro5/resampling/peakResamplingWhitePaper.pdf
I totally realize that not only is this color table really skewed like you say, but also that it deals with just 24-bit files (assumedly in the integer domain?). But... (see bottom paragraph)
The Barbabatch site claims Logic 7 is using the core audio SRC. From
the Bias paper, it would appear that Wave Editor and SoundTrack Pro
are also using it. Note that it is next to last in terms of quality.
I can confirm that Wave Editor is indeed using the CoreAudio SRC.
I'm just guessing here, but I'll bet the one solid turquoise plot
(the one that is dead last) was done doing single precision SSE2
instructions and the ones that have significant light blue
noise/distortion areas were done using the Altivec multiply
accumulate instruction, which should have 12dB better
noise/distortion performance.
To throw this out there, are there any plans for the CA team to ever enhance or improve the SRC? I was always personally completely satisfied with what it is, and honestly I'd take the convenience of the CA SRC (in terms of coding) over the possible ±20dB of clarity found at <-120dB for other methods. I've never yet had a user complain about the SRC quality...
...or is there really no need when it comes to the true floating-point nature of the CA SRC? Is it possible that the "noise" in the charts comes just as much from the 24-32-24 bit conversion?
I may or may not be an audio purist, but at levels as low as -120dB or less, have any tests shown that that stuff is actually *audible* in the end result? Is this just grandstanding in terms of numbers and charts, or does this have real audible validity?