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| − | All modern computers (e.g. dual-core and better) based on Intel, AMD and Nvidia chipsets have two high-speed USB (USB 2.0) controllers on board. That should give you enough bandwidth to be able to record with:
| + | #REDIRECT [[Cameras_and_accessories#USB_controllers]] |
| − | # 2 depth sensors (MS Kinect or ASUS Xtion) | + | |
| − | # or 4 cameras at 640x480 (raw Bayer format) at 60 FPS
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| − | # or 6 cameras at 640x480 (raw Bayer format) at 40 FPS.
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| − | You can check how many USB 2.0 controllers you have in the “Universal Serial Bus controllers” section in Device Manager. Operating system will display USB 2.0 controllers as “USB Enhanced Host Controllers” (not to be mistaken with USB 1.0 “USB Universal Host controllers”).
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| − | [[File:USB_controllers.png]] | + | |
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| − | You should make sure that you have depth sensors or cameras evenly distributed between available USB 2.0 controllers. For example, if you have 4 cameras, you should connect 2 cameras to first controller and 2 cameras to second controller. Device Manager usually shows USB cameras as “USB Composite Device” at the “Advanced” tab of USB controller properties. If you have too many cameras connected to single USB 2.0 controller, you should re-plug them to different USB ports.
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| − | == USB hubs ==
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| − | If several devices are connected on the USB hub and working in parallel, then the USB bandwidth is shared among the devices. Connecting all cameras via single USB 2.0 hub is OK only for low resolution video recording (320x240). To be able to record video at 640x480 and 60 frames per second, you should avoid connecting more than 2 cameras via single USB controller.
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| − | == Potential issues with USB controllers ==
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| − | Some notebook PCs have one of integrated USB 2.0 controllers reserved for docking station. That may effectively halve your USB bandwidth. Desktop PCs should not have such problem.
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| − | If you plan getting an additional USB controller, please be aware of potential problems with USB 2.0 controllers available on the market. Many USB 2.0 controllers are based on defective NEC USB 2.0 chip, not capable of standard USB 2.0 speeds. That's a well-known bug specific only to NEC USB 2.0 chip. By contrast, all NEC USB 3.0 chips are good and do not have this problem.
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| − | Some manufacturers sell what they call a "USB 2.0 ExpressCard" controller for notebook PCs. Many of such ExpressCard controllers are in fact internal USB hubs in ExpressCard form factor. That means they do not add actual USB bandwidth to the system.
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| − | If you plan getting additional high-speed USB controller, we strongly recommend that you get a USB 3.0 controller, just to be on the safe side.
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| − | When setting up a USB 3.0 controller, make sure you configure it to handle USB 2.0 traffic (as opposed to passing USB 2.0 to integrated USB 2.0 controllers in your chipset). There should be a corresponding setting in driver properties or in BIOS.
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