DPC Latency

Aphelion · 24 Mar 2010

First, if you haven't downloaded the DPC latency checker do it now, it's a great tool for checking system real time performance. While there, grab the PDF product sheet as well.

DPC Latency Checker

My Windows 7 machine is used mainly for audio recording and MIDI sequencing so I'm always looking for ways to optimize system performance. By "optimize" I'm not talking about getting every last bit of brute force power out of the system but instead, reducing the effect of the operating system and associated drivers on "real time" performance.

One of the best tools available is the above mentioned DPC Latency checker.

The last time I checked DPC latency I was getting a few spikes in the 600us range, still well within the green so I didn't pay it much mind. The past few days I'd been testing which "services" were unneeded for my use, I had moved several to manual start without any ill effects. Yesterday I just happened to check DPC latency....
Surprise!

The highest reading was 47us.

Here's a pic.

I hate to admit it, I wasn't keeping track of which services I switched to "manual start", DPC latency wasn't my concern so I didn't use my usual method of changing only one thing at a time. While I never had the unusually high spikes in the red, this shows that both services and drivers can affect DPC latency.

Ap

p.s. after this weekend I'll be running checks to find the "offending"

background service.

Aphelion · 24 Mar 2010

If you're getting interruption in audio streams, (pops, cracks, stuttering...etc) it is probably DPC latency, either that or hardware related IRQ or address space conflicts.

The program posted in message #1 can help give an indication where the problem lies, it's an open source free download. (I have no affiliation with DPC Latency Checker)

Ap

whs · 24 Mar 2010

Ap, if you are inclined and have the time, you may want to write a tutorial for the tutorial section. I bet a lot of people would appreciate that because it is one of those subjects that is probably not well known. And there are postings about audio problems quite frequently where a DPC latency check may help - especially with the additional info that the checker provides.

Aphelion · 24 Mar 2010

whs said:

Ap, if you are inclined and have the time, you may want to write a tutorial for the tutorial section. I bet a lot of people would appreciate that because it is one of those subjects that is probably not well known. And there are postings about audio problems quite frequently where a DPC latency check may help - especially with the additional info that the checker provides.

I'd be glad to, I'm having a busy week but as soon as it slows down I'll start work on one.

Ap

whs · 24 Mar 2010

Aphelion said:

whs said:

Ap, if you are inclined and have the time, you may want to write a tutorial for the tutorial section. I bet a lot of people would appreciate that because it is one of those subjects that is probably not well known. And there are postings about audio problems quite frequently where a DPC latency check may help - especially with the additional info that the checker provides.

I'd be glad to, I'm having a busy week but as soon as it slows down I'll start work on one.

Ap

Very good. I will be looking forward to it. If this is your first tutorial, ask Brink to give you a hand. He helped all of us and some things are not obvious when you use the tutorial section format.

electrotune1200 · 24 Mar 2010

Aphelion said:

If you're getting interruption in audio streams, (pops, cracks, stuttering...etc) it is probably DPC latency, either that or hardware related IRQ or address space conflicts.

The program posted in message #1 can help give an indication where the problem lies, it's an open source free download. (I have no affiliation with DPC Latency Checker)

Ap

Thanks for the heads up on this. I'll have to give this a try.

It frustrates me till no end that something in Windows is not quite right with on-board audio. It's been this way since Vista with me, and I was really hoping
Windows 7 would get this right. I eventually just gave up and got a cheap external sound card which solved my audio complaints. It's just a shame that in some cases the only fix is buying an external unit for audio while otherwise, the rest of Windows 7 is just a dream.

Aphelion · 26 Mar 2010

<bump> Just to keep visible for a week or two.

Ap

fireberd · 26 Mar 2010

Good Post. As I use my PC as a "DAW" with Sonar (8.5.3) I'm always concerned with latency. My PC checks good with the DPC checker program and (fortunately) I'm not having any latency issues that affect my recording.

Aphelion · 26 Mar 2010

fireberd said:

Good Post. As I use my PC as a "DAW" with Sonar (8.5.3) I'm always concerned with latency. My PC checks good with the DPC checker program and (fortunately) I'm not having any latency issues that affect my recording.

You're doing well then. Win-7 seems to be giving some folks a lot of grief, not sure if the drivers aren't up to speed yet or the motherboard BIOS setting need to be tweaked. (Not the user BIOS settings but the ones that are changed with a BIOS update).

There's a "Sonar" studio here in town, the owner/engineer/musician has used Sonar since it came out and gets a great sound. That's one of the programs.. along with Soundforge/CD Architect that completely follow the Windows/Microsoft programming guidelines.

Ap

JazzSus · 27 Mar 2010

Aphelion said:

There's a "Sonar" studio here in town, the owner/engineer/musician has used Sonar since it came out and gets a great sound. That's one of the programs.. along with Soundforge/CD Architect that completely follow the Windows/Microsoft programming guidelines.

Ap

Yes they follow MS guidelines because they are build on DirectSound architecture. I started with ProAudio9.3 and Soundforge6. Later on diserted to FLS and Cubase [ASIO architecture] and lately start learning Reaper and Bidul.

Without intention to hijack thread I have something related to latency in MIDI/Audio. That is if you load/import midi file to sequencer and you have SB installed on your computer than probably you dont have latency if you start replace instruments on different tracks with VSTi because SF2 is perfetly syncing. However if you dont have any SB installed and you have to use "Microsoft GS Wavetable Synth" [win build in soundmodule] Than later when you start replacing GM sounds with VSTi you run to sync problem. They sound way different-out of sync. You can try this just load midi tracks with SF2 and trigger metronom on. They will be synced. This doesnt happend when you use Win GM Wavetable. Midi and metronom are out of sync. Question is: Can this be fixed? I think it has nothing to do with DPC latency....or? TIA