Microsoft KB Archive/278516

= USB Multichannel Audio Noise with UHCI Controllers =

Article ID: 278516

Article Last Modified on 2/12/2007

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APPLIES TO


 * Microsoft Windows Millennium Edition

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This article was previously published under Q278516



SYMPTOMS
On a Microsoft Windows ME-based computer, a USB Multichannel Audio device may produce extraneous noise when you select certain channel and bit-depth configurations. This problem is evident on Universal Host Controller Interface (UHCI) USB controllers, but not on Open Host Controller Interface (OHCI) controllers. When the problem occurs, the device typically receives a data packet approximately every 10 milliseconds where the data is all zero (0), and this results in the noise.

This problem is not known to occur on Microsoft Windows 98 or Microsoft Windows 98 Second Edition-based computers.



CAUSE
The problem can occur because of the method that Kmixer.sys, the kernel audio mixer, uses to allocate its mix buffers. UHCI USB controllers cannot typically support transfer descriptors in which the data spans multiple noncontiguous memory pages. OHCI USB controllers do not have this limitation. Under certain channel and bit-depth configurations, Kmixer.sys may allocate mix buffers that span multiple noncontiguous memory pages, which results in this problem with UHCI controllers.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

