[wdmaudiodev] Re: USB2.0 High speed audio device for windows XP

  • From: <carsten_30_@xxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Mon, 18 Feb 2008 21:59:26 +0100

Full ACK,

MS UsbAudio.sys is largely useless!!! I definitly need more bandwitch! Why should I design a USB2.0 Audio device, if I was limited to USB1.1???

So can someone help me with my other question? My own driver (based on AVStream) can handle the high data rate, but I found no way to make this capture filter accessible as a system audio device. It only appears as a WDM streaming capture device.

Some ideas?

thanx carsten


----- Original Message ----- From: "Al Clark" <aclark@xxxxxxxxxxxxxxxxxx>
To: <wdmaudiodev@xxxxxxxxxxxxx>
Sent: Monday, February 18, 2008 9:32 PM
Subject: [wdmaudiodev] Re: USB2.0 High speed audio device for windows XP


As far as I can tell, USB Audio is largely useless if implemented using the built in Microsoft drivers. Its basically 48k, 16 bit, 2 channels.

The Audio Device 2.0 standard addresses many of the problems of the original USB standard but Microsoft has never replaced usbaudio.sys 1.0

Most prosumer gear uses ASIO as a practical workaround. The large audio companies write custom drivers that they can amortize over many units. This leaves the rest of the world with no real USB solution at all.

IMHO, Microsoft could solve a lot of problems by implementing a usbaudio.sys 2.0 driver. It would support the USB Audio Class standard. It should be implemented in both XP & Vista for it to be useful. Sure lots of prosumer gear has ASIO support, but lots of other products do not.

A good driver should support multichannel audio with 24 bit depth (and maybe 32 bit floating point), sampling rates to 192k, low and known latency, etc.

Our company has given up on USB audio. We are moving to Firewire.

I'm by no means knowledgeable about device drivers. By and large, neither are my customers. So please don't blast me, if I have my facts screwed up, instead please enlighten me.

Al Clark
Danville Signal Processing, Inc.








Hakon Strande wrote:

I’ll confirm this with engineering but AFAIK the USB Audio 1.0 class driver is limited to the bandwidth of USB 1.1 spec - BUT - USB Audio 1.0 devices can hook up to a USB 2.0 hub /in the way mentioned below/ so other devices on that hub (like webcams) can leverage the greater bandwidth.

1) The USB Audio 1.0 device connecting to the USB 2.0 hub must have an interval of 4 (interval of 1ms) on the Isoch pipe to match that of USB 1.1.

2) The USB Audio 1.0 device connecting to the USB 2.0 hub cannot be an async endpoint (no feedback pipe).

Sincerely,

* *

*Hakon Strande <mailto:HakonS@xxxxxxxxxxxxx>* |* *Windows Sound Team PM |* *(p) 425.705.0637

*From:* wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] *On Behalf Of *Tim Roberts
*Sent:* Monday, February 18, 2008 11:02 AM
*To:* wdmaudiodev@xxxxxxxxxxxxx
*Subject:* [wdmaudiodev] Re: USB2.0 High speed audio device for windows XP

Hakon Strande wrote:

You can connect a USB Audio 1.0 device to a high speed bus (there are some tricks to this) but bandwidth use is limited by the USB Audio 1.0 spec.


Where? I've been through the whole USB Audio 1.0 spec, and I don't find anything that ties the spec to USB 1.x bandwidth. Indeed, it seems to be very careful to avoid making any mention of "low-speed" and "full-speed" at all.

--
Tim Roberts, timr@xxxxxxxxx <mailto:timr@xxxxxxxxx>
Providenza & Boekelheide, Inc.

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