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Hi,

I am having this setup:

- VirtualBox 4.3.14 r95030
- Guest: Win 7 Ultimate (32 bit)
- Host: Macbook Early 2008, Mac OS X Lion 10.7.5, 6 GB RAM (2 GB of which dedicated to the virtual machine)
- VirtualBox Guest Additions 4.3.14 installed
- The audio settings used are the recommended ones (CoreAudio and Intel HD Audio, respectively).

The audio playback has a clipping-like distortion which appears at random instants. This is the case with any sound I've tried: e.g., system sounds, mp3s through the Windows Media Player, as well as streaming audio from YouTube.

Has anybody else encountered this? Is this a bug or might there be something with my settings?

Thanks in advance.

I don't believe it's a bug because I have no such problems running a Mac host and Windows 7 guest. It may have something to do with your settings or the guest is just taxing the system but I don't know how you could check.

edit: btw, if it sounds like it's clipping even at low volumes then it's most likely a performance problem.

Hi there,

Many thanks for your comment - it was useful. After a lot of searching I'm realising that this may indeed be a performance problem. Still not solved though - see below.

I run the DPC Latency Checker, which gave me an output that looks like this.
(No other application was running on the guest during that time.) No wonder I'm having distorted audio.

Running the Windows Performance Analyzer I found that the drivers most responsible for this high latency are mainly:

- ataport.sys (causing by far the highest latency, from what I can see)
- i8042prt.sys
- ndis.sys
- ntoskrnl.sys

I tried disabling all the drivers that I could disable - the latency problem persists. Furthermore, Windows is telling me that the drivers supposedly need no updating.

I have found VirtualBox forum posts referring to DPC Latency on the host, but not on the guest.

As my Win 7 guest is a virtual machine, I suppose that the problem with these drivers (especially ataport.sys) is not so much hardware-specific.(?)

Does anyone know what might be the problem with this - how do I get ataport.sys and the other drivers not cause such massive latency?

Thanks.

I was just looking at the log you posted. One thing is it seems you have 2D disabled? I couldn't tell but is 3D disabled as well? If so you should enable them. When you installed the guest additions did you install the WMMD driver or DirectX?. You also still have the GA .iso mounted which it shouldn't be. Try fixing up those few things and see if it works better.
Also if you have WIndows Updates set to Automatic that could be an issue. Also any Anti-Virus programs. The more processes running in the guest the more latency. Mine looks much better than yours although part of that is I have a much faster CPU.

Hi,

Thanks for the suggestions.

- Both 2D and 3D accelerations are enabled now;
- Automatic Windows updates and anti-virus program disabled (actually uninstalled it!);
- GA.iso unmounted.

The problem persists, with the same drivers (mostly ataport.sys, but also i8042prt.sys and ndis.sys) being responsible for the latency. Occasionally there are more yellow bars appearing than before, but I'd say it's basically the same problem - most spikes are on the red.

I don't remember whether I installed the WMMD driver or DirectX with the Guest Additions, and I'm not sure how to check this. Which is the recommended one? I think I just installed what was there as default/recommended.

I'm not sure how it could be a processor speed or RAM issue: these high latency spikes are exhibited when CPU Usage is 3-10% and the memory usage is ~470 MB (out of 2 GB).

(PS: Attaching a new log.)

I don't think it's a RAM issue but it could be a CPU issue. You host has to run itself, the virtualbox app, and the guest more or less which could cause latency issues. As far as which one you have installed, if you can run Aero you have the WMMD driver installed. As far as which might be best to use, I guess that depends on what you use the guest for. I have the WMMD driver installed.

Yes, but still, this ridiculous amount of latency is exhibited in the guest when the total CPU usage of my host is only around 30%... So I cannot understand this.

By the way, I can run Aero, so I guess I have the WMMD driver installed. I haven't enabled Aero though, and I won't need any fancy graphics on the guest. I just want to use it to do some programming, especially audio-related software, hence my problem with the latency.

Thank you so far for your comments. If you don't have any other ideas, I think I'll repost my problem with a more clear subject (emphasising on the high DPC latency of the guest) and see if someone else has any more ideas regarding this.