Update available to configure the number of buffers that is used by the USB audio driver to hold audio in Windows 2000 (871244)

SUMMARY

This article describes an update to the universal serial bus (USB) audio driver in Microsoft Windows 2000. This update lets you configure the number of capture buffers that is used to hold audio. By default, the USB audio driver, Usbaudio.sys, submits two buffers at a time to the USB driver stack when you use a USB audio device to capture audio. Each buffer holds 10 milliseconds of audio.

If you install the hotfix that is described in the following article in the Microsoft Knowledge Base, the number of buffers is changed from two to eight:

817865 Windows 2000 USB audio capture may drop isochronous packets

You may want to increase the number of buffers that are used by the USB audio driver in certain situations. For example, increase the number of buffers if you notice that gaps occur in audio that you capture because the USB audio driver periodically drops packets. This update lets you specify the number of buffers that is used by the USB audio driver. To do this, install the update, add the UrbsPerStream registry entry, and then specify the number of buffers that you want to use.

MORE INFORMATION

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

This hotfix requires Microsoft Windows 2000 Service Pack 4 (SP4).

Restart requirement

You must restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Date         Time   Version        Size    File name
-------------------------------------------------------
13-Sep-2004  20:22  5.0.2195.6974  69,264  Usbaudio.sys

Add the UrbsPerStream registry entry

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

After you install this hotfix, add the UrbsPerStream registry entry to the registry, and then set the UrbsPerStream registry entry to the number of buffers that you want. To do this, follow these steps:

Click Start, click Run, type regedit, and then click OK.
Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\USBAUDIO\Parameters
On the Edit menu, point to New, and then click DWORD Value.
Type UrbsPerStream, and then press ENTER.
On the Edit menu, click Modify.
In the Value data box, type the number of buffers that you want to use, and then click OK.

Important We have not tested what occurs if you use more than 24 buffers. Use caution if you set the UrbsPerStream registry entry to a value that is more than 24.
Quit Registry Editor.