Dropped frames upon USB connection event

[Brad]

Lately I've been using a simple USB 2.0 switch to share my keyboard between two computers. (I do have two pointing devices for them.)

I get inserted and dropped frames when I try to do this USB disconnect / connect during a VirtualDub capture.

To ensure that I'm not actually using USB resources during capture and getting some sort of conflict, I tried a capture with one of my PCIe cards writing to internal SATA SSD. Then I removed nearly all resource usage by doing an uncompressed Test Capture (F7), which doesn't write to disk at all. Process Explorer reports that VirtualDub is using less than 0.25% CPU.

Still, the problem remains. I see two processes that spike: an instance of svchost.exe associated with the Plug and Play service (among two others) and explorer.exe.



The purple arrow below indicates CPU usage spikes each time I pressed a button on the USB switch.



Don't tell me I'm gonna have to invest in an actual KVM just to avoid this silliness!

I'm vaguely aware of software solutions for keyboard sharing, but I feel like there must be notable lag.

[Bjs]

Usb is a subset to video so anytime a usb device is disconnected you'll continue to have the problem during video capture ... no getting around it apart from.

Try Synergy ... basic version costs $10, very easy to use

Or Inputdirector

[redwudz]

One of the 'problems' with USB is that the system polls the USB devices all the time to see if they are alive and plugged in and operating.
With USB 1.1 and maybe 2.0 that could cause dropped data to external drives occasionally if too many USB devices were connected.

I suspect the capture might be hanging when one of those USB devices is suddenly missing and USB firmware is doing some checking. Just a guess, though.

I'd try a KVM. I have several of them and they seem to operate seamlessly.

[dellsam34]

Are the keyboards that expensive?

[KarMa]

Are the keyboards that expensive?

Probably just more of a hassle to have to use more than one keyboard if you want to stay seated at the same desk.

[usually_quiet]

Keyboards are cheap enough, but many find it awkward to juggle two keyboards and two mice for two different systems. If I had to do that often, I would definitely invest in a KVM switch or the suggested software.

[Brad]

The issue seems to be limited to my Win7 system. Or possibly its chipset, if not the OS itself?

I just did a capture using a PCI card on a different computer running WinXP (writing to SSD) and wasn't able to make it drop frames when I toggled the switch.

[Brad]

^ Computer 2, which doesn't insert frames upon USB toggle in WinXP, does insert frames when toggling in Win7.

There is another variable I didn't control for (I used a different capture card, the Intensity Pro 4K) but it seems to me this issue is specific to the newer OSes.

[pandy]

You may try to search for better USB port - use Microsoft USBView http://www.ftdichip.com/Support/Utilities/usbview.zip to check ports hierarchy and this one to verify latency http://www.thesycon.de/deu/latency_check.shtml - search for least affected... It works sometimes - not sure if it can help in your case as USB is CPU hog...

[Brad]

Are you saying that I need a better USB port for my keyboard?