Media Servers and Digital Stage Lighting

On Stage Lighting has a beginner’s guide to media servers, digital lighting and some extra skills that could become vital for future stage lighting technicians. Plus, are us lampies now betrothed to the video department? Or will we never actually get up the aisle?

Image by SweetOne on Flickr

If you watch TV shows, rock concerts or big gigs like an Olympic Opening Ceremony, you see some pretty impressive lighting effects. In the background, scenic elements become walls of moving images, LED matrices throb with funky colours and text. It’s all part of the brave new world – Digital Lighting. The idea of using stage lighting and video projection techniques isn’t new but the systems used are becoming more complex and the boundaries between lighting and vision are being blurred. It’s even got a fancy name – Convergence: the convergance of digital media, projection and lighting technologies. More about that later.

What is Digital Lighting?

“Digital lighting”, using digital media in lighting, refers to a couple of different technologies and applications.

• Digital Projection – Using projector technology to throw light with patterns, colours and imagery. This only differs from standard projection in it’s purpose – to create looks, mood and to light a space with digital media.
• Screens and digital array systems – Using LEDs and other pixel light sources to create a screen to replay digital content. A simple array could be a 3 x 3 grid of pars or a more complex flown cloth with a high resolution grid of 3 colour LEDs. This is where the definitions really get stretched – are “screens” really lighting? Well, it’s all part of the visual experience.

Parts of a Digital Lighting System

• Media/Content – to screen or project media in a digital lighting system, you need content. Pictures, clips, algorithms to render.
• Media Playback – servers, players, anything that organises digital content pixels and sends them down a wire.
• Control Surface – The lighting console in many cases, a method to choose, blend and send the digital content. In lighting, we still think of these as cues (for the moment).
• Control System – The method for the different digital elements to talk to each other. DMX or a network protocol.
• Output Devices – Digital projectors, lighting fixtures or arrays/screens. The stuff at the end of the line where it all happens. AKA Producer Pleasers.

What is a Media Server ?

A media server is any device that produces or plays back content for our projection/lighting fixtures. At the bottom end of the scale we have a single laptop running a Windows screen saver, while top notch media systems might consist of racks of dedicated computing power rendering layers of content to a whole bunch of output devices.Hardware media servers ( the big ones in racks) like Axon (often outputting the the High End DL moving head projectors), Hippotizer and Pandora’s Box. Other software based players can be run on a decent laptop and include brands like Arkaos VJ or Grand MA Video. Hell, you can even use Winamp.

How do lighting consoles control a media server?

DMX512 is still pretty entrenched in stage lighting today and it is possible to control the media content using simple DMX signals. Media control layers have a fixture personality and different parameters or selection values. Layer 1 : Intensity 100%, Playlist 1, Item 4, Play, Loop – each DMX channel has an attribute and a value.
However, DMX is a pretty simple protocol that doesn’t have the two way comms that creates good integration of consoles and media servers. Networks (of some sort) are better – ArtNet is a stage lighting orientated network which has wide support and quite a few manufacturer’s have their own network protocol that enable seamless integration with their own media systems. The Grand MA, MA net and GrandMA video are good examples.The benefits of two way communication include:

• Device feedback.
• Media thumbnails and other tools that aid control.
• Control from the device, as well as control via the desk. This is fed back and can be recorded at the console.

Digital Lighting – General Pointers

• Content can be sent to digital lighting devices using a video signal – VGA, Component, Composite. One media server output = 1 piece of projection content. If you need two fixtures to do different things, you need more than one server output.
• Content can be mixed before outputting. Based on mulitple layers, one media output can have a mix/blend a number of different images/gobos/animations etc
• Digital moving lights such at the High End DL have Pan, Tilt, focus, iris and other “standard” lighting functions as well as projector-like controls. The DL also has onboard media serving facilities that are controlled using a laptop utility, effectively uploading your custom gobos/other wobbly stuff to the fixtures playback system.
• In a DMX controlled system, personalities for the fixtures are created for the console in the usual way, with both DMX and Video sent to each projector

But I don’t want to be a Vidiot!

A straw poll of lampies and video engineers around me suggests that none of us feel very “converged”. There nothing much converging about digital lighting – it’s the lighting department nicking technology from the VT boys for our own personal gratification. The idea of being able to create gobos in Photoshop, animate swirly patterns and play back videos to light the stage with is too good an opportunity to miss.

Let’s face it, no one in the video department really appreciates a well focussed DHA leafy break up gobo. That’s what makes us lampies! Let just borrow their kit.

What Skills Do I Need For All This?

Ok, so you are busting to get out there and learn every bit of kit you can get your hands on. That’s great. In the meantime, there are a number of related skills that a stage lighting technician needs. Many of them are already part of the modern world, particularly for anyone who uses IT ( ie nearly everone).

• The basic optics of projection. Like lighting optics with more emphasis on focus and keystoning.
• Digital file types and organisation. Understanding how digital pictures and movies are compressed and displayed – it’s all pretty simple for the Bebo generation.
• Understanding of pixels, rasters and resolutions. PC screens or projectors. This is also a part of successful pixel mapping.
• Basic networking knowledge. Doesn’t have to mean your brain has it’s own IP address – just enough understanding of how devices interact with each other.
• Using layers and masks. Learn something like Photoshop. As well as being able to produce your media server content, the concepts of such software are used in media server content organisation. Layers, opacity, vector masks and alpha channels plus using RGB or HSB colour mixing.
• Much as I hate to be a Vidiot, the basics of the dreaded world of VT. Signal types and distribution, switchers, frame rates. Understanding these mundane things sets the Lighting Designer free to create, making informed choices based on the technology available. LD’s like Richard Pilbrow have always kept ahead of technology, using it for their purposes while remembering the basics of lighting a show.

So, where do you stand on the whole “convergence” thing? Are screens really a job for the lighting department?
Are we all just one big happy family or is there a limit to how integrated you think LX and VT will be? Personally, any technology I can use to good effect is fair game but what are your thoughts?

Let us know in the comments box as usual. See you next time.