The USB device specification limits reliable data transfers over a devices USB cable to around 5 meters or about 16 feet for High-Speed devices. The distance is a bit less for Low-Speed devices like keyboards and mice. An Active USB repeater extension cable can extend the webcam's distance considerably.
Active Repeater cables are available up to 100 feet. Some of the shorter one's simply reamplify and reclock the 5 volt signal coming from your Mac computer's port to extend a webcam (or any other USB device's) range. However for longer distances, you should look for USB extension cables that include a separate power-supply to adequately and reliably boost the signal. Extending a webcam with ordinary USB A-to-B extender cables will likely result in the device disappearing off the USB bus and possibly causing your video application to lock-up or crash.
For some, extending their Mac webcam via Ethernet cabling is preferred for ranges up to 300 feet. Above you see a pair of USB transceivers: One for your Macintosh's USB-A port, and the other end with a power-supply input and USB-B female socket to plug your web camera into.
Lastly, note extending SuperSpeed USB 3.0 devices (not webcams) required different, USB3 certified cabling and extenders. That's not an issue for Mac webcam users since NO web cameras made currently require nor operate at USB 3.0 speeds. All Apple-friendly UVC compatible webcams are USB 2.0 speed devices.
USB Video Class compliance isn't just for webcams. Analog video capture gadgets, Digital video cameras, still image cameras, USB TV tuners and other video devices can leverage the evolving UVC device specification. The latest version of the spec is now at v1.5 and is incorporated into (notably) some of Logitech's most recent premium webcams for Mac and PC.
The USB-IF Video working group at USB.org is chartered with updating the current USB Video Class (UVC) specification to natively support modern encoders like H.264. H.264 is an open standard that allows highly efficient video compression techniques for reducing the use of network bandwidth as well as significantly decreasing drive storage space requirements.The USB-IF working group also addresses known limitations with the UVC Specification and adopts new features to address evolving product technologies and market demands. Area of interest to the UVC working group include:
- Native H.264 support - Flexible metadata for each video frame - A windowing API for digital sensors - Ability to set a Region of Interest in the camera's field of view - Support for additional color spaces and color depths
- QOS - Quality Of Service scaling and negotiation - Support for additional video codecs - Support for multi-view stream management - Support for scene content depth information
In terms of the latest UVC 1.5 spec, H.264 and QOS matter a lot. There so many different video devices - from cell phones to PC and Mac desktop computers to dedicated group conferencing platforms. Available internet bandwidth can vary greatly. And delivering the optimal video resolution, image quality, or frame and data rates appropriate for each device is an important challenge the UVC committee strives to address.