With the rise in popularity of LED products on the market, it’s practically a given that at some point you will find yourself working with pixel mapping. This can be very easy, especially when the content you intend to use is loaded onto the media server that’s doing the pixel mapping. But what do you do when a client has a content playback device that does not output Art-Net or DMX, does not have a pixel mapping interface, and only outputs a video signal? If you have a media server with a video input card, then you’re in luck! You can use that for another creative purpose beyond simply displaying output from a camera. How? By converting a video signal to DMX values for pixel mapping. Video to DMX
Recently I found myself in this situation on a project where the video team was using a multi-display presentation system that did not have a pixel mapping function internally, nor did it output DMX/Art-Net beyond a single universe. So, knowing the content from this device needed to be mapped onto LED Pixel tape integrated into the edges of the stage, and that it had to somehow be converted into DMX values, we set out to find a solution.
After we put our heads together to discuss the concept and searched the web for any type of products that might already exist for this purpose, we decided to make use of one of the four video inputs on the media server we had specified on the show: the Mbox Extreme. By connecting the display system to the Mbox via SDI, it would allow us to use the Mbox’s internal pixel mapping functionality, and it would effectively give us a way to take in a video signal and convert it to RGB DMX values for the LED Pixel tape.
Challenges
In order to make this work, a couple of technical details needed to be addressed.
Challenge #1: For starters, the multi-display system could only output DVI, and the video inputs on the Mbox are only SDI. So step 1 was to pull out an Image Pro from our bag of tricks to handle the signal conversion. This worked like a charm, with no issues getting the signal out of one device and into the other with minimal frame delay. A side note on frame delay: The content to be pixel mapped in this case was ambient background type of stuff, and at such a low resolution we were hopeful that it would be nearly impossible to see any frame delay if one existed.
Challenge #2: The next step was to figure out the necessary image resolution. The overall image being output by the multi-display system was around 4K; however, Mbox supports 1920×1080 resolution on a single output. This meant that the original content had to be scaled to fit the Mbox’s maximum output. Luckily, the content creator was available to do this in order for this to work. And he provided me with a nice template that I could use for creating the pixel map in Mbox as well. One additional note: although the height of the image was relatively small (255 pixels), the template width was 1660 pixels, which made working in single RGB pixels tedious and time consuming. That’s important to point out in order to ensure you have plenty of time to build the pixel map.
Challenge #3: Pixel Tape refresh rate, power supply voltage, and DMX drivers, moreover, are always a big question mark, so it’s definitely worth setting up a mock up test ahead of time before the LED tape has been installed into scenic pieces to ensure there is no flickering or issues with the DMX refresh rate. As I’ve experienced on a few occasions now, the DMX refresh rate of the console and the LED drivers have to be the same or there can be huge signal problems. And, unfortunately it can be difficult to pinpoint the exact refresh rate of LED tape once it’s installed, and often times results in relying on a third party device like the DMX Decelerator from Doug Fleenor (dfd.com/dmxdecel.html) or the DecaBox DMX Slowdowner from Engineering Solutions (response-box.com/gear/shop). Better to plan for this ahead of time than to be caught on show site unprepared!
Challenge #4: An additional challenge was, as always, organization. Staying organized was critical for the success of a show with 38 universes of pixel tape being controlled. As the image shows (see Fig. 1), each universe was marked with its total pixel count and assigned a box number and universe. That box number and universe was my only way to make sure I had the right pixel on the right box patched to the right address in my console. It’s essentially my lighting plot, and it’s the guide by which I can create a working pixel map while not losing track of where I am at while working.
Comfort Zone to End Zone
In the end, although we hit some snags along the way, I learned a lot from going through the process of working through these issues. And using the video input as a converter for the incoming video signal to DMX RGB values worked consistently, both in the shop and on show site. So, the next time a client throws a concept at you that you’ve not tried before, my advice would be to take a look at the gear you do know how to use and see if you can utilize a feature it has in a different way and push yourself out of your comfort box. The payoff is well worth it!
