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Part 2 - Why USB 3.0 for AV & USB cabling limitations/extensions

Part 2 - Why USB 3.0 for AV & USB cabling limitations/extensions

 Why USB 3.0 for AV?

Why use USB 3.0 for AV?  The 5Gbps data rate available with USB 3.0 allows us to send up to 1080p-30 uncompressed video directly to a PC.  This is especially useful for soft codec and web based video conferencing solutions like Lync, Skype, Hangouts, WebEx, GoToMeeting, Jabber, etc...  USB 2.0 is also capable of carrying 1080p-30 resolution but it must first be pre-compressed by the camera (e.g. via H.264 compression) in order to squeeze into the 480Mbps limitations of USB 2.0.  Most cameras do not have this compression built-in but more importantly many applications perform better if the conferencing, streaming or recording software is the only step in the signal chain providing compression to the video stream.

USB 3.0 Cabling Length Limitations and Extensions

USB 2.0 cable lengths were limited by specification to about 5m or 16.5’.  While USB 3.0 cable length is not specifically limited by the specification, the effective max cable length is even shorter at about 3m or 10’.  This is fine for connecting appliances to a PC at your desk but will not suffice for installations in larger spaces (e.g. control rooms, conference rooms, auditoriums, etc...).


Luckily, there are solutions for using USB 3.0 beyond the 3m limit.  They all require another medium (e.g. proprietary cabling of predetermined length, twisted pair cabling or fiber optic cabling).

Examples of proprietary cabling include both passive (no additional power required) and active (additional power required for electronics in the extension cabling). 


Passive extension cabling is typically limited to about 2m or 6’.  Longer examples exist but may not perform at HD video rates like 720-60 and 1080p-30.  A single extension to your original 6’ USB 3.0 cable is all that you will get to work reliably in most video applications. 

Active extension cables are pre-terminated and so purchased for the length you require.  Active extensions can be from 3m (10’) all the way up to 20m (>60’). Examples of active extension cabling are available from SIIG, ATEN, Tripp Lite, TetherPro, C2G (formerly cable2go), Sabrent, StarTech and others.  These cables come with a power supply that typically gets plugged into the device end (e.g. camera) of the cable.  Therefore, an additional outlet will be required for this power connection at the device.  These cables can often be daisy chained (once) to effectively double the distance.  This daisy chain, however is not a viable solution if the daisy chain connection happens to fall inside a wall cavity where it cannot be observed or maintained.  Most if not all of the currently available active extensions are also not plenum rated for installation in/across a closed ceiling.

Twisted pair (CATx) solutions for extending USB 3.0 do exist.  However, with data rates at 480Mbps (the USB 2.0 data rate), they are not fully USB 3.0 capable and so are not viable options.

For most professional installations in walls and across ceilings, fiber optic is the preferred solution.  Examples of fiber optic extenders include those from Icron, Blackbox and others. A fiber modem pair is required with a “remote extender” at the device end and a “local extender” at the PC end.  While the local extender may be powered directly from the 900 mA available on the PC’s USB 3.0 port, the remote extender will need to be powered at the device end (just as the active extension cable is), as power cannot be sent over glass fiber.  As with active extension cabling, plan for an additional AC outlet at the device as well as a place to mount the remote extender box within a 2m cable length of the device.  Fiber optic cabling can be purchased with both plenum and non-plenum ratings and in pre-determined lengths or as bulk cabling to be terminated by a competent fiber optic installer.  The availability of plenum fiber optic cabling and the 100m (328’) cable range of these solutions make fiber the ideal extension medium for installed USB 3.0.

Part 3 - USB Troubleshooting & Managing USB Power Settings


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Everything you need to know about USB 3.0 - Part 1
Part 3 - USB Troubleshooting & Managing USB Power ...

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