Real-time audio suitability checker. LatencyMon checks if a system running Windows is suitable for processing real time audio by measuring DPC and ISR excecution times as well as hard pagefaults. It will provide a comprehensible report and find the kernel modules and processes responsible for causing audio latencies which result in drop outs. It also provides the functionality of an ISR monitor, DPC monitor and a hard pagefault monitor.

LatencyMon will display the execution time of each ISR, DPC routine and hard pagefault and will resolve them to the drivers and processes responsible for executing them. It will create a comprehensible report but it will also represent all sampled data in a detailed manner allowing you to perform in-depth analysis.

The audio latency problem
Windows is not a real time operating system. All requests to the operating system are delivered on a best effort basis. There are no guarantees whatsoever that requests are delivered within a certain time frame, which are the characteristics of a real-time operating system. That is not a problem for most devices and tasks but this is bad news for audio applications (which are considered soft real-time) because they need to deliver data to the subsystem and the hardware in buffers several times per second. If one or more buffers miss their deadlines and are not delivered in time it has audible consequences which are recognized as dropouts, clicks and pops.

Using LatencyMon
1. Starting and stopping LatencyMon
When LatencyMon starts, it will start with a screen that displays a message to click the Start button. Click the start button. Now wait or run your audio software. Activities regarding DPC, ISR and pagefault executions will be listed under under the Monitor tab while the Report tab will display a comprehensible report with a conclusion. When you are done click the Stop button.

2. Report view
At the top of the screen, the report view displays a conclusion about the suitability of your system for playing real-time audio at the top. If the execution times of all DPC and ISR routines stay below 2000 (microseconds), your system is considered suitable for handling real-time audio without dropouts. If some routines have execution times between 2000 and 4000, your system is considered doubtful. If ISR or DPC routines are detected to execute for longer than 4000 , a system is considered unsuitable for handling real-time audio. Note that these numbers are just chosen arbitrarily. For optimal midi to audio latencies, buffer sizes of a sound card and driver should be set to very low values then only very low execution times of DPCs and ISRs become acceptable.

The license of this software is Freeware, you can free download and free use this system monitor software.