Some time ago I stumbled over an article about DPC (Deferred Procedure Call) in Windows and the issue of latency problems regarding that process.
Problem:
In essence, DPC relates to a CPU tunnelig process in which all streaming media (audio/video playback/recording etc.) in Windows are subjected to. Transferring data to and from a soundcard requires the device driver to send a DPC request to the CPU. As Windows can't multitask by design, each CPU-Core has only one queue for all hardware. It's a first in first out principle and the timing and flow is subject to whatever is happening in all running tasks, processes and services regarding hardware at the time.
This process is the basic problem for all audio malfunctions, there might ofcourse be other issues but if DPC latency is low and stable the problem is certainly found in either audio software or hardware settings.
How to fix and maintain sound issues:
DPC latency can be monitored in real time with this magnificent tool from Thesycon Systemsoftware. Being German, they also write thorough procedures on how to use it so I'll leave it to them to explain the process of eliminating problems. A more in depth explaination of DPC is also found on the bottom of that link.
In addition to their information - It's important to note that services, scheduled tasks and startup processes also should be checked in addition to drivers while verifying DPC latency. Many 3rd party services (and sometimes Windows services like diagnostics and similar) do heavy communication with hardware. These should be disabled while monitoring DPC latency to see what effect they have on your computer. As for software, all kinds of Media Centers, iTunes, integrated security software etc. usually installs heavy background processes cluttering up the system and should be avoided.
By trial and error over years using Windows based studios and live performance software I've found that every problem, especially on Win 7, have shown up on the DPC latency checker, thus making them easy to eliminate by following the above examples using Thesycon's benchmark.
For all of you with audio problems out there I hope this helps - Good luck!
Regards,
Rainer
Problem:
In essence, DPC relates to a CPU tunnelig process in which all streaming media (audio/video playback/recording etc.) in Windows are subjected to. Transferring data to and from a soundcard requires the device driver to send a DPC request to the CPU. As Windows can't multitask by design, each CPU-Core has only one queue for all hardware. It's a first in first out principle and the timing and flow is subject to whatever is happening in all running tasks, processes and services regarding hardware at the time.
This process is the basic problem for all audio malfunctions, there might ofcourse be other issues but if DPC latency is low and stable the problem is certainly found in either audio software or hardware settings.
How to fix and maintain sound issues:
DPC latency can be monitored in real time with this magnificent tool from Thesycon Systemsoftware. Being German, they also write thorough procedures on how to use it so I'll leave it to them to explain the process of eliminating problems. A more in depth explaination of DPC is also found on the bottom of that link.
In addition to their information - It's important to note that services, scheduled tasks and startup processes also should be checked in addition to drivers while verifying DPC latency. Many 3rd party services (and sometimes Windows services like diagnostics and similar) do heavy communication with hardware. These should be disabled while monitoring DPC latency to see what effect they have on your computer. As for software, all kinds of Media Centers, iTunes, integrated security software etc. usually installs heavy background processes cluttering up the system and should be avoided.
By trial and error over years using Windows based studios and live performance software I've found that every problem, especially on Win 7, have shown up on the DPC latency checker, thus making them easy to eliminate by following the above examples using Thesycon's benchmark.
For all of you with audio problems out there I hope this helps - Good luck!
Regards,
Rainer
My Computer
At a glance
Windows 7 Ultimate x64Intel Core i7 96012GB Mushkin DDR3 Triple ChannelZOTAC GeForce GTX 560Ti 1GB PhysX CUDA
- Computer Manufacturer/Model Number
- -
- OS
- Windows 7 Ultimate x64
- CPU
- Intel Core i7 960
- Motherboard
- Gigabyte X58A-UD3R r13
- Memory
- 12GB Mushkin DDR3 Triple Channel
- Graphics Card(s)
- ZOTAC GeForce GTX 560Ti 1GB PhysX CUDA
- Sound Card
- M-Audio ProFire 610
- Monitor(s) Displays
- Samsung SyncMaster 226BW + Benq FP222Wa
- Screen Resolution
- 3360x1024
- Hard Drives
- RAID 2x OCZ 120GB SSD S-ATA III (System)
RAID 2x Seagate 1TB S-ATA III (Recording)
1x WD Black Edition 7200 2TB
2x WD Black Edition 7200 1TB (Sample archive)
2x WD Caviar 7200 500GB
1x Cavalry Caum 7200 2TB
- PSU
- Thermaltake Toughpower XT
- Case
- CoolerMaster Stacker v2.0
- Cooling
- Antec KÜHLER H2O 620
- Keyboard
- Logitech diNivo Laser Desktop
- Mouse
- Logitech MX-900
- Internet Speed
- VDSL 40/10
- Other Info
- It is a DAW. Mostly.
