Real-time, low-latency audio applications like DAX rely upon consistent, uninterrupted audio bit streams to and from the radio and PC for proper operation.
If the DAX RX or TX Streams are interrupted by DPC's (Deferred Procedure Calls) and Hard Page Faults, the system can experience DAX Buffer overruns or underruns. This can cause "clicks and pops" on transmitted audio, distortion on TX or RX in the DAX feed, choppy audio, or other issues.
See this article for more information about DPC's: What are DPCs and Why Do They Matter? – FlexRadio
Running a program such as LatencyMON provides system-level insight into how various drivers and programs may be affecting your live audio stream: Using LatencyMon to collect DPC Latency Data – FlexRadio
Mitigating DPS's and Hard Page Fault issues:
Here are several steps you can take to mitigate these issues:
Do them one at a time and see if the issue improves after each step.
1. Check for the maximum CPU Load while operating your digital modes.
- Tap the "Windows" Key and start typing "Task Manager," and select the option to open Task Manager.
- Click on "Performance" and select CPU Load
- Monitor this graph while operating your Digital Mode. The CPU % Utilization will spike every time the program is doing major calculations -- for example, during the "decode" cycle in WSJT-X
- If the CPU % Utilization spikes over about 85%, it can trigger a DAX Driver Overrun or Underrun.
This can cause TX Distortion, TX "Clicks and pops," Dropped Decodes on Receive, and other disruptions, which can be cleared up by closing and reopening the DAX program. (Until the next error happens.) - If you are experiencing this issue, you will need to reduce the load on your CPU by reducing the number of instances of the digital program you are running, closing other high CPU usage programs (web browsers, streaming video programs, video games, etc).
2. Assure your computer is up to date by running all Windows Updates.
If your computer has uninstalled Windows Updates in the queue, they can load the system and cause latency (delays). Additionally, software updates could improve the system's audio performance.
- Close SmartSDR, DAX, and CAT, and reboot your computer.
- Run Windows Update as many times as necessary to ensure that there are no remaining updates waiting in the Update Download queue.
- Reboot the computer again.
3. Check the "Power Management" and "Green Ethernet" settings on your computer,
Improper setting of these parameters can cause the Ethernet ports, CPUs, or disk drivers to power down or throttle your network traffic, resulting in network disconnects or interruptions in DAX Streaming.
A) Turn off any power-saving features on your Ethernet card.
- Click the "Window" Key.
- Type "View Network Connections" and click the menu item.
- Right-Click on your "Ethernet" connection and select "Properties."
- Click the "Configure" button for the Ethernet adapter.
- Click on "Power Management" and "un-check" the line that says "Allow the Computer to turn off this device to save power."
- Now click the "Advanced" tab and scroll down the list, and disable the following menu items that may be in the list:
"Energy Efficient Ethernet"
"Green Ethernet"
"Power Saving Mode"
All of these settings, if active, may cause your computer to pause or throttle down your Ethernet adapter if it thinks that there is not enough traffic on the cable. This could result in disconnects or erratic behavior in certain cases.
B) Adjust your computer's "Advanced Power Settings."
- Press the "Windows" key. "Type Edit Power Plan"
- Set your computer to "Never" sleep.
- Then click "Change Advanced Power Settings".
- Turn off any options for CPU, Memory, Ethernet, and Wifi (if you use wifi) that would allow the computer to power any of these settings off automatically to "save power." They may save a little bit of power, but they cause network issues on live streaming applications (like SmartSDR & DAX)
4. Update Your Computer's BIOS
- Download and install the BIOS from your computer manufacturer's or computer motherboard's website.
- (Do not trust Microsoft Update to give you the proper BIOS for your computer.
5. Update Network Drivers
- Download and install updated Ethernet and WIFI drivers from your computer manufacturer's website.
- (Do not trust Microsoft Update to give you the proper Drivers for your computer.
6. Update Video Graphics Drivers
- Download and install updated Video / Graphics drivers from your computer manufacturer's or Video Card's website.
- (Do not trust Microsoft Update to give you the proper Drivers for your computer.
7. Check your computer system for file system and OS corruption:
- Run this procedure to check and repair your file system and OS:
How to Run DISM and SFC on Windows 11 to Repair System Files and Fix Component Corruption – FlexRadio
8. Update your Realtek Audio Driver
- Press the "Windows Key"
- Type "Device Manager" and select it
- Go to "Sound, video, and game controllers" and click on it to expand the list.
- Look for the "Realtek Audio device,"
- Right-click on it and select "Uninstall device".
- Download and install "Realtek HD Audio Driver:" RealTek Driver Download. Select the 64/32 bit driver for Windows - Driver Only (Executable File). The latest version at the time of this article is R.83. Refrain from using
- Run it and follow the on-screen instructions to reinstall the driver
9. Adjust Network Adapter Interrupt Moderation Settings
Some network adapters have Interrupt Moderation settings that can impact system latency. Adjusting these settings may help.
- Press the "Windows Key" and type "Device Manager", and select it
- Look for "Network Adapters"
- Expand the "Network adapters" tab and right-click on your network adapter.
- Select "Properties"
- Go to the 'Advanced" tab.
- Look for "Interrupt Moderation" or "Interrupt Moderation Rate."
- Set it to Disabled or Off.
These steps may help mitigate many DPC and Hard Page Faults, but will not eliminate all of these issues.
Some of these issues are inherent in the design of many computer motherboards, making some computers more suitable for real-time, low-latency audio applications than others.