USB Video Capture frame rate drop after waking from Standby

Archived from groups: microsoft.public.windowsxp.device_driver.dev (More info?)

Our USB Video Capture device running on XP on USB 2.0 runs
at 30 fps. However, if we put the system into Standby mode while
capturing a video (either capturing to file or simple video preview)
then when the system awakes the video capture resumes but at a
frame rate which now fluctuates around 24fps and goes as low as as
22 fps. It is visibly slower - not just a quirk in frame-rate reporting.

This reduction in frame rate is not cumulative. i.e. if we repeatedly
go into Standby mode and reawaken it remains at around 24fps.

The framerate can be is restored to 30fps by simply stopping and
restarting the video capture application.

The problem does not occur if we attach our device on a USB 1.1
port; the framerate then remains constant through Standby/Wake-up
cycles.

We have tried to test this on other vendor's USB video capture
devices to determine if it is a problem in our drivers but to date
have not yet found one that can survive running an application
through a Standby/Wake-up cycle without other, far more serious
problems.

Any assistance, or redirection to a more appropriate forum would
be appreciated.

Steve Thorpe