Over the years, we have been involved in several large-scale LED control projects, typically involving addressable LED tape being placed around a structure. LED tape suffers from a particular problem: it requires a huge number of DMX channels to control it, and a lighting board or media server which is sized to suit. Some productions will already have suitable hardware available, but for those that don’t, our media playback server aims to fill that brief.
The media server is designed to run under Linux on modest hardware; it can even be run on a Raspberry Pi. It does not have a user interface: configuration is by way of text files at present, although a web interface will be added soon. The media server is entirely controlled by only 42 DMX channels: either using a physical DMX connection, or via Art-Net.
The media server controls connected LEDs via Ethernet and the Art-Net v4 protocol using a private network. This protocol is ideal for this purpose: it works well with a switched Ethernet architecture, meaning that the switch will only send traffic to relevant LED Pixel Controllers.
When configuring, a virtual screen is defined with a typical resolution, e.g. 1920×1080. The configuration file permits rows and columns of LEDs to be defined within this virtual screen. Each row or column can be mapped to one or more Art-Net DMX universes. The media server automatically maps pixels to locations within the virtual screen. This automatic scaling also facilitates mapping onto non-flat surfaces: for instance, we have used this feature in the past to map a rectangular virtual screen onto a sphere. The configuration mechanism is very powerful: it is not necessary to define each pixel individually, and hence massively reduces the configuration time required.
For playback, the media server supports most video file formats. Content is placed inside a dedicated folder, which may reside on a removable USB drive if required. To facilitate selection of media files via DMX, files must be named numerically from 0 to 255, e.g. 0.mp4, 1.mkv, 2.webm etc. Content may be placed in different folders, again numbered numerically from 0 to 255.
In terms of control, it is possible to adjust brightness, contrast, hue, saturation and gamma correction remotely via DMX. The media server also supports test patterns, e.g. SMPTE colour bars, colour blocks and so on. Up to 4 media files may be played simultaneously; each player can be assigned a Z-order, and faded up and down. Transport controls include play, pause and reverse, looped play, reverse play, and slow or fast playback.