Grayscale doesn't show when use Staples' USB hub

[mikeincinci]

With the V100 camera plugged directly into the computer, none of my grayscale video programs work if a Staples 7-port, brick-powered USB 2.0 hub is also plugged into the computer. The tracking stuff works fine. Nothing else is plugged into the hub. I have not tried any other hubs, including D-link. I am using Version 1.1.032 beta 01 of SDK.

[Birch]

Adding the hub in may be reducing the amount of USB bandwidth available to the camera. You may want to try increasing the frame decimation setting or using the frame rate feature to slow the camera down a little.

And if you haven't checked it out, here is a FAQ entry on the topic.

[andriyp]

We are having a similar problem with our setup of multiple C120 cameras. When using sample applications, we can only see the grayscale images when a C120 camera is the only camera in the hub. Even though the other cameras in the hub are not active (i.e. not even initialized). Otherwise, there are lots corrupt frames. Unplugging cameras fixes the problem. As soon as you plug the cameras back (as soon as they appear in the Device Manager) the frames start getting corrupted.

Is that a hardware limitation of the cameras?

[VincentG]

What type of hub are you using?

Does it have it's own power supply?

[Birch]

Having other USB devices (cameras, etc) connected to the hub, even if they aren't streaming data, reduces the bandwidth available to each device on the hub. The reduced bandwidth can cause cameras running in grayscale mode to not be serviced fast enough to avoid dropping some data.

The solution, as mentioned in the earlier post, is to adjust the frame scaling, frame dropping, and frame rates on the cameras in grayscale mode to reduce their bandwidth requirements.

Additionally, there is only a certain amount of bandwidth available per EHCI USB controller. The theoretical limit is 60 Megabytes/sec but in practice its closer to 20-30 Megabytes/sec. Running a single C120 in grayscale at full frame rate is about 12 Megabytes/sec. Typically there are one or two controllers on the system, distributing the cameras between these can increase the bandwidth available to them. Using different ports does not guarantee the devices will be on different controllers. You can also use add-in USB 2.0 cards to gain additional controllers.

[andriyp]

It's a "Belkin Hi-Speed USB 2.0 7-Port Hub", like in http://shopper.cnet.com/hubs/belkin-hi- ... 19202.html

And, yes, it is powered.