If your computer is experiencing drop outs when you are listening to an audio or watching a real time video steaming, sometimes it can be caused by a kernel-mode device driver in your Windows system is implemented improperly. Few days ago ha14 posted an interesting tool called DPC Latency Checker in forum. The DPC Latency Checker is a Windows tool that analyzes the capabilities of a computer system to handle real-time data streams properly. It may help to find the cause for interruptions in real-time audio and video streams, also known as drop-outs.

According to THESYCON the creator of DPC Latency Checker, Windows is not a real-time operating system and processing of streaming data in real-time is a very challenging task for Windows based applications and device drivers. There is no guarantee that certain (periodic) actions can be executed in a timely manner. When I first downloaded DPC Latency Checker, I had no idea how to use it because there are nothing except a moving graph showing my computer’s current latency. Actually it’s pretty simple to use and diagnose your computer’s latency with this tool.

This is what I see when I run DPC Latency Checker on my computer. Most of the time the current latency is pretty low and stays below 500 µs. There are a few spikes here and there but it goes just slightly above 1000 µs.

However if you see occurrence of excessive DPC latency is indicated by a red bar like the image below, it means that your computer has drop-out problems.

To find out which driver is the culprit that causes the excessive DPC latencies, you can try disabling individual devices using Windows Device Manager. Go to Control Panel > System > Device Manager. In Device Manager, disable individual devices, one at a time. To disable a device, right-click on the corresponding item (e.g. on the Ethernet adapter) and choose Disable from the context menu. Windows marks a disabled device with a read cross. After you disabled a single device, carefully watch DPC Latency Checker. When excessive latency values disappear you found the responsible device driver. If there are still exceptional large DPC latencies try the next device.

When you have identified the device driver which is responsible for the drop-outs consult the device vendor’s Web site or customer support to find an update for this driver. If this is not possible you may decide to keep the concerned device disabled while you are using streaming applications.

There are a lot of hardware devices listed in your Device Manager. You should not disable devices that are essential for your computer to function such as keyboard, mouse, IDE/SATA controller, display adapter or any device listed in Device Manager under System devices or Computer. In many cases DPC latency problems are caused by specific types of devices. So you should try the device types listed below first.

Network adapters for Ethernet and Wireless LAN

Internal modems

Internal sound devices (on-board sound systems)

Any PCI or PCI Express add-on card, any PCCard or ExpressCard, e.g. TV tuner cards, ISDN or DSL adapters, modems, etc

[ Download DPC Latency Checker ]

DPC Latency Checker is a free and portable tool that runs on Windows 2000, XP, XP x64, Server 2003, Server 2003 x64, Vista and Vista x64.

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