Signal Distribution 101: Baluns, Matrix Switchers, and Format Converters

If you read the title of this article and thought “What the…” don’t worry, you are reading the right article, and once you get past all the jargon, it really is simple and clear. Our aim is to familiarize you with the tools that help you move your video and audio signals from one device to another. To accomplish this, you may need a variety of baluns, matrix switchers, and format converters. What are they? Let’s find out.

Baluns

Balun, or the plural baluns, pronounced like “VAL-un” but with a “B” instead of a “V,” and “un” as in underwater. The word comes from a contraction of balanced and un-balanced, as in balanced electrical and unbalanced electrical signals. It is, simply, a transformer that allows you to convert a balanced electrical signal to an unbalanced electrical signal or an unbalanced electrical signal to a balanced one. Where you find these in use in the video field is when running a video signal over (in most cases) Ethernet cable (often colloquially referred to as “Cat5” cable; though Cat6 and Cat7 may also be used). Why would you want to do this, you wonder?

Video signals run over a variety of cables, very often RG-6 coax. However, these cables, being unbalanced and, therefore, prone to picking up interference, often have a limited maximum length without using repeaters. Apart from being balanced, Ethernet cables, in general, tend to be easier to snake through walls for installations and are generally cheaper when bought in bulk, because the requirements for cable construction are different. With a baluns setup you need to have a “transmitter” to adapt the video cable to run over the balanced Ethernet cable, and then a “receiver” at the other end, to convert it back to a conventional cable type. Baluns can be powered passively or by use of a power supply, and are available to convert a variety of video signals, including composite, component, VGA, DVI, HDMI, and SDI.

Kramer BNC M Compression Connector for RG-6 Coax

Format Converters

Unlike a balun, which alters the way a video signal travels, format converters process the signal to normalize it to a given standard. Format converters aren’t new, and have existed since ancient analog days, when they were known as “standards converters.” Today, you will mostly find digital-to-digital format converters, although there are still some analog-to-digital converters out there. For example, if you want to connect your VHS player to a TV that only has HDMI inputs, you will need a signal converter from S-video or composite video to HDMI. Beyond the analog-to-digital converter, most of the format converters you find will do one or both of the following: Convert from SDI to HDMI and/or HDMI to SDI (cross conversion) and scale the signal. Some format converters will also convert the frame rate of your video. Format converters are not limited to HDMI/SDI, you can also find converters from analog to digital, digital to analog, HDMI to VGA, DVI to SDI, and many more options. Click here for listings of the format converters available on the B&H SuperStore website. Although many field and on-camera monitors now include cross conversion between SDI and HDMI, a dedicated format converter can be a useful item on a set and, for installations, it can be an invaluable tool.

DECIMATOR MD-HX Miniature HDMI/SDI Cross Converter with Scaling & Frame Rate Conversion

Matrix Switchers

Put simply, a matrix switcher is a device that has more than one input and more than one output and enables mapping any input to any output or multiple outputs. The smallest a matrix switcher is a 2x2 (two input and two output). This is different from a production switcher, which has multiple inputs, but only one output—the program output. Yes, some production switchers have multi-view outputs, and auxiliary outputs but those, in general, are specialty outputs. The program output is the main output. This is also different from a distribution box that will take one input and feed it to multiple outputs. With a matrix switcher, you can have multiple inputs and route them to different multiple outputs if you wish. These can be excellent devices for a facility that has a central “machine room” with decks or media players and must send video to different rooms in the facility. Important features of matrix switchers include independent frame buffers on each input and the capability to scale the resolution and change frame rate.