Hello Geert I wonder if you might be able to help with a more general AC2 issue. In the list of Key Differences, the Release 2.0 device class definition for Audio Devices document states that split off the examples in a separate document. Did any such document ever get published? Is there a draft available perhaps? Given the (sad) paucity of AC2 compliant devices such a document would be extremely helpful for implementors Many thanks Jerry From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Geert Knapen Sent: 14 February 2014 23:09 To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Re: USB Audio Class 2.0 May I suggest to have a look at Section 2.1 in the Audio 2.0 spec: 2.1 Overview of Key Differences between ADC v1.0 and v2.0 The following list is not an exhaustive list of all changes that have been introduced. For complete information, refer to the full specification. Pay special attention to Sections 1 through 6! · Complete support for high speed operation - no longer are audio class devices limited to full speed operation. · The notion of physical and logical Audio channel clusters. · The number of predefined spatial locations has increased. In addition, a virtual spatial location called Raw Data was introduced. · Use of the interface association descriptor - The standard Interface Association mechanism is used to describe an Audio Interface Collection. The former class specific mechanism was deprecated. · Descriptor updates: fixed offsets associated with many descriptors and enlarged three byte fields into four bytes. · Extensive support for interrupts to inform the host about dynamic changes that occur on the different addressable Entities (Clock Entities, Terminals, Units, interfaces and endpoints) inside the audio function. · More clarification text on the audio function. · Audio Control Changes. o Control attribute changes. o Mixer Unit control request (set/get pairs changed). o Many updates in the control descriptions. · Added support for clock domains, clock description and clock control. · Added additional Audio Controls inside a Feature Unit (Input, Gain, Input Gain Pad ...) · Added bit pairs in descriptors to indicate presence and programmability of every Control · Prohibited the use of Alternate Setting switching to change sampling frequencies. Instead, Clock Entities are introduced that can be manipulated (through the AudioControl interface) to select operating sampling frequencies. · Split off the examples in a separate document. · Allowed binding between physical buttons on the audio function and the corresponding Audio Control. Prescribed how this is done. · Added an Effect Unit to group algorithms that work on logical channels separately but require multiple parameters to manipulate the effect (as opposed to basic (single parameter) manipulation, performed in a Feature Unit). · Introduced Parametric Equalizer Section Effect Unit. · Rearranged Reverb, Modulation Delay and Dynamic Compressor PUs under the new Effect Unit. · Added the concept of audio function Category. The Category indicates the primary use of the audio function as envisioned by the manufacturer. · Added the Sampling Rate Converter Unit. · Added a means to express Latency of individual building blocks within the audio function. · Added Encoder support. Of course, these are all technical differences and do not necessarily directly translate in specific reasons to invest in Audio 2.0 :-) Kindest Regards, Geert Knapen USB Audio DWG Chair <http://www.designandadvice.com> Image removed by sender. D&A <http://www.jwhouse.org> Image removed by sender. JW HouseGeert Knapen <http://www.designandadvice.com> Design & Advice, L.L.C. 1725 Martin Avenue, San Jose CA 95128 e-mail: <mailto:geert@xxxxxxxxxxxxxxxxxxx> geert@xxxxxxxxxxxxxxxxxxx | Tel: +1-408-297-3731 | Cell: +1-408-507-7852 | Google Voice: +1-408-805-4320 On Feb 14, 2014, at 2:45 PM, Matthew van Eerde <Matthew.van.Eerde@xxxxxxxxxxxxx> wrote: Specific reasons to invest in USB Audio 2.0: * Higher bit rate enables more formats * Dynamic jack presence detection * Anything else? -----Original Message----- From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Børge Strand-Bergesen Sent: Friday, February 14, 2014 2:38 PM To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Re: USB Audio Class 2.0 Thank you Phil. The market demands Hi-Res, science of not. Microsoft will sell more OS licenses with UAC2 support. Apple will sell less Macs with Windows UAC2 support. Enough to justify the investment? I think yes. Enough to get a measurable peak on the first quarterly report? Probably not. Børge P.S. I'm sorry for going OT with the mention of megapixels and MHz. I'm just trying to see the world of electroncis through the eyes of the people browsing the shelves at Best Buy. Having a number to compare will tip their scale. Lots of users will ignore the not easily quantifiable quality of the optics if the other camera has more pixels. Currently, UAC2 DACs don't play out of the box, and they sell to customers who care about the quality of the optics. Make them play out of the box and they will sell to the much larger crowd which doesn't. P.P.S Don't forget the placebo effect. This DAC has more X than that other one, so it _must_ sound better. No UAC2, no cake! On Fri, Feb 14, 2014 at 7:42 PM, Philip Gruebele <pgruebele@xxxxxxx> wrote: 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. -phil 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: http://www.youtube.com/watch?v=mNzr6lfiHJE (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. 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