Problem
USB bandwidth saturation causes one or more cameras or capture devices to intermittently disconnect.
Solution
Root Cause / Diagnostic:
USB 3.0/3.1 root hubs share a finite total bandwidth pool (typically 5 Gbps across multiple physical ports routed to a single Host Controller). Connecting multiple high-resolution capture cards (delivering uncompressed YUY2 or high-bitrate MJPEG video) saturates the bus's isochronous data transfer capacity. When endpoint bandwidth limits are breached, the USB controller drops packets or resets the device connection, causing cameras to freeze or disconnect.
Actionable Fix:
1. Distribute capture devices across separate root host controllers by plugging them into different physical USB bus clusters (e.g., front-panel vs. rear I/O motherboards).
2. Change camera capture video format in OBS Device Properties from uncompressed YUY2 to compressed MJPEG or NV12 to cut USB bandwidth usage in half.
3. Use Device Manager (View by connection) or USBView utility to verify that each video capture endpoint operates on an independent USB Host Controller.
Pro Tip:
Install a dedicated multi-channel PCIe USB expansion card (such as a PCIe card with 4 independent controller chips) to eliminate shared bandwidth bottlenecks permanently.
USB 3.0/3.1 root hubs share a finite total bandwidth pool (typically 5 Gbps across multiple physical ports routed to a single Host Controller). Connecting multiple high-resolution capture cards (delivering uncompressed YUY2 or high-bitrate MJPEG video) saturates the bus's isochronous data transfer capacity. When endpoint bandwidth limits are breached, the USB controller drops packets or resets the device connection, causing cameras to freeze or disconnect.
Actionable Fix:
1. Distribute capture devices across separate root host controllers by plugging them into different physical USB bus clusters (e.g., front-panel vs. rear I/O motherboards).
2. Change camera capture video format in OBS Device Properties from uncompressed YUY2 to compressed MJPEG or NV12 to cut USB bandwidth usage in half.
3. Use Device Manager (View by connection) or USBView utility to verify that each video capture endpoint operates on an independent USB Host Controller.
Pro Tip:
Install a dedicated multi-channel PCIe USB expansion card (such as a PCIe card with 4 independent controller chips) to eliminate shared bandwidth bottlenecks permanently.