X51 High DPC latency on Windows 8 causing audio pop/crack ?

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X51 High DPC latency on Windows 8 causing audio pop/crack ?

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Hi Folks,

I discovered something new yesterday and just wanted to share it with others. I have an X51 which I upgraded to Windows 8 in October - I've had no problems thus far until I discovered something yesterday as follows:

In my X51 I had thus far left the Realtek HD audio "Waves MAXXAudio" setting in the default "MaxSense On" state which is supposed to improve sound. I decided to turn the Waves MAXXAudio off completely in order the experience my system without all the extra audio processing. To my amazement, Battlefield 3 was a completely new and amazing experience with the default sound (without MAXXAudio enabled I had to up the volume a bit) !!  The guns sounded absolutely more powerful and real compared to when MAXXAudio was enabled (I use the Famas BTW :). It turned out that the MaxSense setting has the MaxxLeveler  feature turned on by default which dynamically tries to normalize the volume, hence, gunfire in Battlefield 3 was being muffled.

I decided to keep MAXXAudio off and started listening to some music while browsing - then I discovered a problem. Occasionally when I opened a content heavy web-site, I would get a slight click/pop in audio sometimes - this would happen occasionally, but was definitely noticeable.  Why did I not notice this earlier when MAXXAudio was ON ? I turned ON MAXXAudio and to my amazement, the click/pop was there - not as pronounced as with the setting turned-off, but it was there. Having MAXXAudio ON reduced the effect of the click/pop, but since I was actually trying to listen for it, I was able to notice it.

Interestingly, with MAXXAudio off, the audio is perfect while on-line gaming in Battlefield 3 - only when browsing the web do I get the occasional clicks.

My research of this problem on-line has pointed to a potential cause: in the way Windows 8 handles interrupts - interrupts is a mechanism used by the OS to  communicate with any hardware (mouse, keyboard, audio, video, etc). Speaking broadly, apparently in order to be more power efficient (Windows 8 is optimized to run on Smartphones/Tablets which run on batteries), Windows 8 changes the way interrupts are handled compared with older Windows versions possibly resulting in high latency. This latency, if high enough, can affect real-time tasks such as audio processing resulting in pops/cracks.

There are tools that can expose this high latency.  This first tool is DPC Latency checker which is not recommended for Windows 8 as it reports persistently high latency of 1000 uS every second for Windows 8 - the webpage mentions this problem and a fix should be coming soon.  The correct tool to use is LatencyMon - I installed and ran it, and lo and behold, there is definitely a latency problem !

I have a screen shot of the LatencyMon window after it captured the high latency event - I simply ran LatencyMon and started browsing the web.

LatencyMon specifies the culprit driver as ndis.sys 6.30 which is the new network driver interface for Windows 8 from Microsoft - the latency is around 19851 us. As indicated in the image, this is most likely related to the WLAN adapter.  I have an Intel N6200 wifi installed and I've tried all kinds of things to get rid of the ndis.sys problem - updated drivers, changed, power settings, etc, but no luck. I don't know if the latency is high with the default Dell Artheros Wifi as well.

In order to verify what I have discovered with regards to high latency in Windows 8, could someone with an X51 running Windows 8 please try the following:

1. Turn off MAXXAudio, turn up the volume, start playing some music and start browsing the web. Spend around 10 mins and go to content heavy web-sites - do you notice an occasional pop or click ?

2. Download and run LatencyMon while browsing the web. What latency numbers are being reported ? Are they High ? Similar to what I have ?

It would be good to know if this is a real problem with Windows 8 with regards to the handling of real-time events such as audio.

PS: You may have to run LatencyMon  in "administrator mode" in case it refuses to start.

Verified Answer
  • Ok .. so I found the culprit for the high latency after a lot of further digging on-line. The offender is Norton Anti Virus - specifically the "Intrusion Prevention" component in NAV. Intrusion Prevention inspects TCP packets and compares them against offending signatures - connection to the computer that generated the offending packet is severed if it matches the offending signature. This seems to increase the latency of ndis.sys significantly.

    Disabling the "Intrusion Prevention" component from NAV eliminates this latency - now I'm getting max 4 ms latency on heavy content web-sites, and audio no longer pops or crackles.

    This may solve the problem for others as well if they 're facing a similar situation.

All Replies
  • Ok .. so I found the culprit for the high latency after a lot of further digging on-line. The offender is Norton Anti Virus - specifically the "Intrusion Prevention" component in NAV. Intrusion Prevention inspects TCP packets and compares them against offending signatures - connection to the computer that generated the offending packet is severed if it matches the offending signature. This seems to increase the latency of ndis.sys significantly.

    Disabling the "Intrusion Prevention" component from NAV eliminates this latency - now I'm getting max 4 ms latency on heavy content web-sites, and audio no longer pops or crackles.

    This may solve the problem for others as well if they 're facing a similar situation.

  • Incompressible

    I appreciate you posting about the issue and updating us on the cause.  This may well help others with similar issues.

    Great post,

    Thanks

    TB