There are 4 main units in the BrightSign product line (there are a few others available for hardware integrators, but I’m ignoring these for now and am only looking that the units in their own cases).
The LS line of the bright sign players is compact. It is idea when working with a single HD stream at up to 60 frames per second. It also offers a single USB port for connecting to other peripherals.
The HD line can decode a single 4K video stream. With the HD line of players a GPIO port is also added to allowing additional hardware to be connected to the player for other forms of interaction.
These units are set apart from the HD line in being capable of decoding up to 2 4K video streams and have an improved HTML rendering capabilities.
These are the most capable Brightsign units, able to decode two 4K video streams at once. Some of the units in this family also feature an HDMI in allowing them to mix in video from another source with content. These units have 2 USB ports (USB-A and USB-C). They can also be powered via PoE.