Range Extenders: An Essential Live Production Tool

Tim Siglin

If you read the product review of Gefen’s Extender for HDMI 1.3 over CAT5 with Ethernet (a long name for a product that combines HDMI 1.3, IR, and Ethernet over one Cat5 cable) in the inaugural issue of EventDV Live next month, you’ll see just how blurry the lines are getting when it comes to the combination of streaming and live local display. And this presents an opportunity for live production teams to offer clients new services.

For live events, whether they include one camera or multiple cameras mixed through a video mixer, such as the TriCaster TXCD300 (SD/HD) or TriCaster Pro (SD only), the need to project the camera’s image on a big screen is becoming a standard client need. Often, though, as I mentioned in my first blog post, the client will forget to request this up front and will also lack particular equipment needed to perform image magnification (IMAG). So, having a range extender handy will allow you to provide a needed service, and possibly increase your revenues while saving the client the much-higher cost of calling in an AV integrator just to get your camera signal on to their projector or screen.

By a range extender, I mean a point-to-point, high-resolution graphics transmission system. Using existing data networking cable infrastructure to transmit a VGA, DVI, or HDMI signal several hundred feet (across copper) up to several kilometers (across fiber) from a playback device, such as a DVD player or camera, to a monitor or projector.

Almost all range extenders, whether within a single large room or in a campus-wide distribution, use a pair of converter boxes tied together to send and receive a VGA, DVI, or HDMI signal. The transmitter box converts a digital or analog RGB connection, such as a DB-15 for VGA, for transmission across the Cat5 cable or fiber, while the receiver box converts back from Cat5 or fiber to the traditional cabling connector. The copper cabling used to tie these transmit and receive devices together can be Cat5, Cat5e, or Cat6, but are often referred to generically as Cat5.

The lines get blurrier. Since these range extender products use the same cabling as data networks, often times “borrowing” a set of Cat5 cables to create a point-to-point delivery, there is often confusion as to whether the signal being sent over these range extenders is a data signal. In other words, can it be plugged it into an Ethernet switch?

The short answer is no: While Cat5 cabling is being used, the signals being sent down the cabling do not correspond to Ethernet packets. See the product review mentioned above for a more detailed answer.

As we move beyond analog signals, such as VGA, to digital signals, such as DVI and HDMI, the industry is at an interesting inflection point about the potential of range extenders to mature to a point of playing nicely with Ethernet. Since these newer signals are already digital, the thought goes, could the processing time required to convert an analog signal to a digital signal be re-allocated to create a packetized version of DVI or HDMI?

The short answer is maybe. Three issues are at play here, which we’ll touch on briefly in this post as well as in a product review for a product that begins the span the gap between Ethernet and point-to-point range extenders:

First, bandwidth. While Cat5 cables are capable of bi-directional (transmit and receive) at 100 megabits per second (100 Mbps), the data signals for DVI or HDMI would require at least 1 gigabit per second (1 Gbps), and as much as 1.5 Gbps. Low-end Ethernet switches and cabling often can’t keep up with this demand.

Second, error control. HDMI Range extenders use all the cable pairs on a Cat5 cable as a way to split the 1.5 Gpbs across multiple cable pairs, with an appropriately fast receiver at the other end. Some solutions even use a second Cat5 cable to handle projector or monitor control. The speed at which encoding, delivery and decoding occurs leaves little room to re-request missing data. Plus, that’s not exactly Ethernet’s strong point, as it was built as a “best effort” network protocol.

Third, price. The price point of a 1 Gbps switch is extremely attractive, with non-managed 8-port switches well below $100, but the same can’t be said for the necessary 10 Gbps switch that would be required for the signal to be sent to multiple locations. At this point, it’s cheaper to buy multiple point-to-point systems than it is to consider 10G switches, but that may well change within the year.

In conclusion, having a range extender kit in your bag is a great way to offer a service to your live event customers. It takes up a small amount of space but can easily pay for itself on the first project.