Friday, May 25, 2012

Digital Media Certifcation

For those who just joined us here  - or who have been here from the first but forgot - I'm currently on a journey from an AV Project Manager role to an AV Project Engineer role. De facto, I'm almost exclusively doing PE work, but before I get to change the  title on my business card I need to collect all of AVI-SPL's official requirements. Along the way, I'm picking up the skills and knowledge to better be able to handle the work.

This week I finished another step - Crestron's three-day Digital Media Certified Engineer training class.This was sometimes interesting, sometimes humbling, and an excellent addition to my AV education.
Digital Media was introduced seven years ago (it doesn't seem like that long!) when digital video was still primarily associated with consumer applications. The idea was that you could take various video formats (S-Video, VGA, composite video, HDMI), convert them to a digital signal and send them over a single cable to your display. The original solution (which we now call "DM Copper" to distinguish from newer versions) included transmitters at source locations, switches, and receivers at the destination. All of these were connected with Crestron's proprietary Digital Media cable. This cable,  about the diameter of a garden hose, contains three individually jacketed cables - an 8 conductor UTP which looks just like a Cat5, an 8 conductor STP (this carries everything but audio and video) with a rigid spline down the center to separate the pairs (this carries audio and video), and a 4-conductor control cable for communication and power of the transmitters and receivers. Since then, they've added "DM 8G" which uses a single shielded twisted pair (regular Cat5e or 6 works), as well as multimode fiber solutions. It's an important technology to be comfortable with, as Crestron has recently sold their 50,000th DM switch, and shows no signs of slowing down.

What was the DMC-E class like? It's a combination of Creston's other two DM classes - DMC-D (Designer) and DMC-T (Technician). The goal was that, at the end of three days, I'd be able to lay out a DM system, put it together (including cable terminations), test and commission it. It was quite a bit to pack in to three days!

We started with the "D" part, reviewing the alphabet soup that goes with digital video - HDMI, HDCP, EDID, CEC, TMDS, and even a brief mention of SDI. It's all stuff that I mostly have by now, but did add a couple of details about, for example, exactly how CEC works and how we could use it in the unlikely case that we found a reason to do so. For those who don't know, CEC is an absurdly slow control protocol embedded in HDMI video. The idea is that any bit of equipment can trade control signals with any other. So, if you turn on your Sony Blu-ray player, it can automatically switch on your Panasonic TV and flip it to the right input. The problem is that many manufacturers don't want to make it too easy to use competitors' gear, so they use their own proprietary codes as part of the "extended" command set. In the commercial world, of course, we just turn these things off.

Day 1 ended with a fairly detailed review of the capabilities and limitations (most frustrating limitation - that DM systems only support USB 1.0, while many interactive touchscreens require USB 2.x. There seem to be no plans to improve upon this) available digital media hardware, some applications exercises, and a test. This was a fairly easy day for me, and relatively fun.
Day 2 covered the "T" part of the certification. This was, for me, the humbling part. In my project manager role, I'd become often handed a drawing set to a team of technicians and taken for granted that they'd fly through it, quickly and accurately terminating and connecting all manner of cables. While I can put together a standard or even shielded RJ45 connector if given enough time, the multi part DM connectors quite honestly gave me fits. I'd not wrap enough braid around the inner jacket and leave the cable loose. Or leave the conductors too long so the strain relief didn't grip the outer jacket. Or just plain wear out the little teeth inside the connector from having to open and close it too many times after putting one pair in backwards. I'm sure that if I did this kind of work every day I'd get better at it. I also know that after a half day of working on one connector, I discovered new respect for the people who do it everyday and can even manage more than one termination per hour. Frustration notwithstanding, I did manage to head home at the end of Day 2 leaving working DM Copper and 8G cables behind.

We also got to try our hands at a fiber terminations, which was half safety lesson and half actual work. Fiber safety is pretty simple; it's made of glass. You don't want to eat glass, you don't want glass in your eyes, and you don't want glass splinters. So wear goggles, don't eat where you're working on fiber, and if you break a piece off clean it up and throw it away. Putting the connector on a fiber-optic cable is a step-by-step process that feels as if it should be happening in a laboratory. Mark it with the measuring card, strip the outer jacket, strip the inner jacket, wipe clean, cleave with the cleaving tool, realize that you forgot to put the little boot over the cable, swear at yourself while you try to carefully slide it past the now naked fiber without breaking it, slip the end into the connector, screw it together.

Day 3 was the putting it together and testing day - back to my comfort zone. We hooked up all those cables we made to a DM switcher, transmitters, receivers, controller, and a couple of monitors and then got to play with it. I must confess that it did take some of the sting out of the ours toiling over connectors to get to hook them up and see them work.  The theory is fine, but there really is nothing to compare with actually logging into a system and seeing just what you can make it do to confirm that you actually have learned something.
At the end of the day we took a test, showed the instructor that we got our system to work, and got our official certificates. And that is our technology post for this week. Tune in next week for the penultimate installment of the blog-hopping "Riley's Story" .

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