[wdmaudiodev] Re: USB Audio Class 2.0

  • From: Philip Gruebele <pgruebele@xxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Fri, 14 Feb 2014 13:42:21 -0500

Three points worth making:

1. Whether or not it is technically necessary to support higher sample rates is not relevant. What is relevant is whether the market demands it, and it undeniably does. Otherwise why would so many companies - hardware manufacturers and download services - invest so many resources to make it happen?

2. Using Nyquist and human hearing to make a case for not supporting higher sample rates is looking at the issue too narrowly. The reason higher sample rates can be better are complex and include things like simplifying DAC design and out-of-band filtering. Also some protocols like DSD64 over DoP require 176.4Khz and DSD128 requires double that just to get the data across. UA2.0 also supports certain use cases which are not possible with UA1.0. The minimum sample rate that should be supported is at least 384Khz and UA2.0 has handled all these cases for many years.

3. The lack of USB Audio 2.0 support causes a headache for consumers because they have to deal with low quality, poorly test, third party drivers. These drivers are not going away because of point (1). There are a LOT of high-end audio enthusiasts who voted against Windows by using Apple products because they provide a better end-user experience.


Tim Roberts wrote:
Børge Strand-Bergesen wrote:
I'm sorry Tim, but this is like saying Canon & Co. should have stopped
adding megapixels once their cameras got 4 or so of them.
No, this is not a valid comparison.  Our eyes can tell the difference
between 300dpi and 600dpi, and a 4MP camera can only do about 200dpi
when printed at 8.5x11.  Those extra pixels ARE being put to use.

The same is simply not true of audio.  You don't "zoom in" on an audio
track.  The concept doesn't make sense.  The best human ears are
physically unable to sense frequencies above about 20kHz.  Per Nyquist,
anything above twice that frequency serves no purpose at all.  They
CANNOT, physically, alter what we sense in the sound.

It reminds me of the "Dominator DMX 10" scene from Ruthless People:
(Caution: language)

kHz is a simple number. Comparing the kHz of your audio system will be
done in the consumer crowds just like they compared the MHz of their
CPUs and the megapixels of their cameras. The more you have of that
simple metric, the better they will feel.
That's voodoo, not engineering.  Those MHz and megapixels are being
used.  Those extra kHz are utterly pointless.  Unlike the other two, we
have reached a physical limit.


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