We did reach the limits, or nearly, but then we backed way off from the limits, and stayed back. 128kbps MP3 is most certainly NOT reaching the limits of human hearing, for instance.
So to the extent that a push for 24-bit files will result in higher sampling rates in the kinds of files most folks are listening to, yeah, it could be a big help. Especially if you are talking about my field, classical music, where the dynamic range involved is much wider and the variety of sounds involved is much greater.
Will it be the 24-bitness that causes the improvement? Not directly, no.
I was talking about 16 bit, 44.1 kHz, not 128 kbps MP3 [0]. Oh, and the sampling rate has nothing to do with the bit depth. 44 kHz gives you frequencies up to 22 kHz, that’s at least two kHz better than great human hearing. I don’t see any possible reason why a higher sampling rate would be necessary.
I also would like to know what you mean by 24 bit causing an improvement indirectly. How so?
[0] I attended a university lecture with one of its main inventors and he told us in no uncertain terms that 128 kbps MP3 is definitely not CD quality and also that MP3 has certain artifacts (castagnettes are its enemy) that cannot be remedied by simply picking a higher bit rate. Lossy audio compression is still extremely clever and cool.
Yeah, but my point was, most of us are no longer listening to 16/44.1 CDs. We're listening to MP3, AAC, etc. If we were still listening to CDs directly, there wouldn't be an issue.
What I mean by the push for 24-bit causing an improvement indirectly is, Apple (and others) aren't stupid. They aren't going to just up the size of the sample to 24 bits and leave the sampling rate and overall quality alone. They're doing this to offer much larger files, probably 24/96 files, with either lossless compression or much less lossy compression, so they can a) sell those files for more money and b) justify folks purchasing new audio players and huge amounts of storage to store all their new shiny files. My point is therefore that 24-bit will drive an overall improvement in quality, hopefully to something greater than CD quality.
Ah, ok, that’s understandable. I would, however, be much happier about lossless music that doesn’t needlessly waste storage space. Mobile storage space is still limited, especially after everyone switched to flash memory.
(I’m personally happily buying 256 kbps AAC files. I did a blind test before I started investing money and couldn’t hear the difference. Buying and storing lossless files would be kind of pointless for me personally.)
Note that the anti-aliasing filters necessary to cut off audio at 22 kHz distort the audible range, too. Also, what they don't cut off gets introduced into the lowest frequencies as noise (this effect is called aliasing). With a higher sampling rate, you can use less steep anti-aliasing filter slopes that introduce less distortion and noise. Furthermore, that distortion can be limited to frequency ranges above the human hearing threshold. Hence, higher sampling rates can make a huge difference.
There is no such thing as a perfect, distortion-free filter.
This is where oversampling comes in, and you get CD players with 196khz 1 bit DACs - we mathematically shift samples to a much higher bitrate (at lower sample width), and then run it through a dac - that allows for a much, much gentler filter, as artifacts are shifted way higher in the spectrum. This is already a solved issue......(even if sales guys a decade or so ago tried to claim it increased resolution - oversampling was all about gentler filters and cleaner sound, not increased resolution, as we know that's impossible)
Oversampling only improves DACs (CD-plyers, sound cards), it does not solve anything for ADCs (mastering). When mastering a CD, the antialiasing filter still needs to shut off at 22.050 Hz and there is nothing oversampling can do to improve this.
You can use really long, linear-phase look-ahead FIR filters that are way better than the analogue IIR filters of the olden days, but the filter slopes still have to cut off between 18-22 kHz, which means some ~60dB+ per octave. A filter like this will always produce audible artifacts. This is pure physics and there is nothing we can do about this.
Is there a major music store that only sells 128-bit MP3 (or equivalent AAC or ATRAC etc.)? Amazon and iTunes sell 320kbps mp3's, and most smaller sites I know of make WAV or FLAC versions available.
So to the extent that a push for 24-bit files will result in higher sampling rates in the kinds of files most folks are listening to, yeah, it could be a big help. Especially if you are talking about my field, classical music, where the dynamic range involved is much wider and the variety of sounds involved is much greater.
Will it be the 24-bitness that causes the improvement? Not directly, no.