How to Overcome USB Limitations in Conference Room Audio Systems

Mike Brandes of QSC Systems says an AV-to-USB Bridging solution will allow designers to overcome the geographical challenges of meeting room spaces and provide true flexibility to users wanting more than one concurrent USB interface.

CI Staff

A few years ago, there wasn’t much of a use case for integrating professional AV systems with endpoint destination for computers; today it’s practically a necessity.

End-user applications require the computer to be a destination for a number of applications: computer-based video conferencing, recording, lecture capture and CDN rebroadcasting, to name a few. As more customers are refreshing legacy installations or provisioning future projects, the need for PC integration will become almost ubiquitous.

As its name suggests, Universal Serial Bus (USB) is an ideal interface technology for connecting just about any type of signal (video, audio, network or control) to a computer. Manufacturers have seen the incredible demand for this and have developed a suite of products to convert just about any signal to USB.

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While USB interfaces allow system designers to easily integrate traditional audiovisual equipment with computers for capture and conference, distribution of USB signals into even the simplest projects can become difficult and create more problems than they solve.

USB connections maintain a 1:1 relationship between the devices and the host. For instance, without additional equipment (like a KVM or USB switcher) I cannot use my USB mouse on multiple computers, and I certainly can’t use it on multiple computers at the same time.

In most traditional conferencing solutions, you will experience the same limitation when trying to connect a conference camera feed to multiple computers.

To do this, you need a USB switch (which may or may not work appropriately with some devices) and a control system to control the switch to be able to choose which PC will be the destination. Once the switching element is in place, the challenge of distributing these signals to endpoints still needs to be addressed.

Routing USB signals over 10 feet requires an extension cable of some sort, which is often the source of USB audio-related issues. There are a number of USB 2.0 and 3.0 cables in the marketplace.

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These products use electrical repeaters every 10-15 feet to maintain the signal integrity. The effectiveness of these USB extension options is sketchy. It can be difficult to pull these bulky cables through conduit, and they are often not plenum rated.

Another option when it comes to extending USB signals is a long-distance active optic cable. Using fiber-optic cable, USB signals are converted to light for transmission long distances. These solutions aren’t as prevalent due to the associated costs, both in material and labor; also at times these devices aren’t able to register “hot-plug” events, preventing devices from fully registering to a computer.

The easy, and typically inexpensive, way to distribute signals in our industry is to do so over category cable, using a transmitter and receiver scheme. Category cable-based extension solutions are easier to integrate (physically pulling the wire) and are often less expensive (category cable is fairly inexpensive) compared to active USB cables, especially as distance between the transmitter and receiver is increased.

The downside to extending USB audio, especially in real-time applications (computer-based conferencing, for instance), is that only a select few transmitters and receivers fully support the Isochronous transfer mode. Those that don’t fully support the Isochronous transfer mode can introduce audio distortion or sample-rate errors into the equation, leaving the users of the AV system frustrated and unable to communicate with one another.

QSC recently introduced a USB/network paradigm for conferencing called the Q-SYS AV-to-USB Bridging solution. It uses the same USB interface, or bridge, between the audiovisual system and a user’s laptop, tablet or in-room PC, and uses Ethernet for long run distribution instead of extending USB.

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Using standard networking equipment, users can place either a QSC TSC-7t touchscreen controller or a Q-SYS I/O-USB Bridge and have USB connectivity wherever they need it. This also eliminates the 1:1 paradigm of traditional USB audio solutions.

Using the AV-to-USB Bridging solution allows designers to overcome geographical challenges often associated with meeting room spaces, without additional hardware costs and risk, as well as provide true flexibility to users wanting more than one concurrent USB interface.

Author Mike Brandes is product manager at QSC Systems.

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