I am running three video sources. Two Logitech C920 cameras and an iPhone>HDMI>USB device listed as USB Video. I have followed the setup instructions on each respective device to the tee. The issue I am encountering is that only some of the devices will initialize on startup of the program. If I disconnect the two C920 cameras, my phone display works perfectly. If the program launches with the two cameras attached, sometimes only one of the cameras will work and the phone display will not work at all.
Video Capture Failing
- Thread starter GBCxPrime
- Start date
FerretBomb
Active Member
Sounds like you're running into USB bus bandwidth choke. c920s are USB 2.0 devices, and a single 1080p30 video stream can eat a significant portion of the bandwidth available. Two will eat more than the spec provides (why USB 2.0 1080p60 capture is awful, it has to be compressed to fit in the bandwidth available). A third USB capture device will go even further.
Be aware that even if you have a LOT of USB ports on your computer, multiple are connected to the same USB Host Controller Interface chip (UHCI). All devices connected to the same UHCI have to share a communal pool of bandwidth.
Even worse, USB 2.0 devices connected to a 3.0 interface still have to comply with the same low bandwidth problem, even if the 3.0 host controller has more available. It can't 'upconvert' 2.0 devices to 3.0, even if there's plenty of 3.0 bandwidth available, thanks to a patent by ASMedia (and the upconverter chips they sell costing around $120 each just for the chip).
You may need to buy a USB expansion PCIe card just to get another UHCI to attach one of the cameras to, for bandwidth reasons.
They actually sell multiple-controller cards just for this sort of problem (that run around $120-150), with four USB ports, and a dedicated UHCI for each single port.
Be aware that even if you have a LOT of USB ports on your computer, multiple are connected to the same USB Host Controller Interface chip (UHCI). All devices connected to the same UHCI have to share a communal pool of bandwidth.
Even worse, USB 2.0 devices connected to a 3.0 interface still have to comply with the same low bandwidth problem, even if the 3.0 host controller has more available. It can't 'upconvert' 2.0 devices to 3.0, even if there's plenty of 3.0 bandwidth available, thanks to a patent by ASMedia (and the upconverter chips they sell costing around $120 each just for the chip).
You may need to buy a USB expansion PCIe card just to get another UHCI to attach one of the cameras to, for bandwidth reasons.
They actually sell multiple-controller cards just for this sort of problem (that run around $120-150), with four USB ports, and a dedicated UHCI for each single port.