This article describes a hotfix rollup for the USB audio driver, Usbaudio.sys, for Windows Vista-based and Windows Server 2008-based computers. This hotfix rollup fixes several problems and provides some improvements for the USB audio driver.

This hotfix rollup fixes the following problems:

• Some legacy USB MIDI devices do not appear in Windows Vista or in Windows Server 2008. These USB MIDI devices correctly appear in Windows XP.
• Some USB Audio devices display incorrect device names.
• In a USB Audio device, you cannot select the output source of a multiplexer (MUX) processing unit.
• A USB Audio device does not log to the same location as the Audio engine does.
• Surprise removal of a USB Audio device causes an application to stop responding or to use 100% of the CPU.
• The USB Audio driver incorrectly maps the center frequency to an incorrect value.
• The USB Audio driver cannot set a specific mode for a processing unit node.

This hotfix rollup includes the following improvements:

• The USB Bus drive can store a device startup failure.
• The USB device can save and restore the MIDI Processing Unit (MPU) state.
• The USB Audio driver can lock the AVStream queue on entry to standby or on exit from standby.
• The process for determining whether a USB Audio device is a communications device has been refined.