The most important question to as is how many sources do you have to send to how many different destinations? This will determine the “size” of the matrix you will need. In most cases matrix systems come in blocks of four or eight inputs/outputs. So for example you can get a 4 x 8 or a 6 x 32 and so forth. Smaller numbers of inputs are available so you could consider a 2 x 8 type configuration if that is appropriate to your application.
Matrix switchers come in a wide variety of capabilities and functionality, and depending on the specific unit a matrix switcher can route composite video, S-video, component video, serial digital video, HDMI, DVI, or RGB computer-video, with or without stereo audio. Determining precisely what you need to accomplish is essential to choosing the right product for the job.
Matrix switchers are available in both fixed architecture formats (that is, what you buy is what you have and no expansion is feasible without adding a second unit) and expandable versions. Many manufacturers offer expandable configurations usually in a card frame structure that allow you to purchase a specific size up front and then expand it with additional plug in cards or frames as your needs change. The cost of the more flexible systems is generally higher initially.
Most matrix switchers can accommodate multiple signal types within a single unit; however, for the most part a signal type that is input can only be routed to an output of the same signal type. In other words, composite video inputs can only go to composite video outputs. There are units available that can perform a transcoding function and convert video formats, but verifying what any specific unit can do and what kind of conversions it can perform is essential.
Determine where the matrix will be located is crucial so that both input and output cabling runs can be kept as short a feasible; the longer the cables, the more likelihood of potential signal quality degradation and other issues. Extenders, boosters and similar devices can and routinely are employed to accommodate longer runs, and increasingly the use of fiber optic connections both for input and output can dramatically limit the occurrence of the kind of problems long runs of copper can create. Be sure to carefully plan out your cable plant and location, and also carefully calculate the distances involved to allow for any additional hardware that you may need to ensure good signal quality and integrity.