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Mr. Wizard Explains the Laserdisc

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The Laserdisc format first hit the market in 1978, using massive 12" discs crammed full of shiny analog video to deliver awesome movies to your 80s-tastic home theater. The players were beastly -- large, heavy machines with complex laser systems and enough oomph to rotate the disc at up to 1,800 rpm. I have still have mine, along with a few movies on Laserdisc that were never released on DVD (for years, my copy of Koyaanisqatsi on Laserdisc was a prized possession, before DVD and Blu-ray versions finally appeared).

Today, the Laserdisc format feels positively retro, and a little clunky. For one thing, depending on the format of the disc, you had to get up and flip it over every 30 or 60 minutes -- unless you had a super-fancy player that could move its laser to the underside and continue playing automatically. There were also single-sided discs (these were less susceptible to laser rot, and were often used for Criterion Collection releases) that were unflippable, so you'd have to eject the big-ass platter and put in the next. In any case, there was no way you could sit through a feature film on Laserdisc without some fiddling; I recall seeing some films in college that required four or five disc swaps.

But despite its compromises and vague clunkiness, Laserdisc was a remarkable invention. It had special features (explained in the video below) sometimes called "trick play" that allowed for high-quality slow motion, full-fidelity still frames, and even individually addressable frames (some educational software allowed the user to pull up individual photographs by selecting a single frame on the disc -- this was how my high school biology class learned about a real condition called "black hairy tongue"). Laserdisc was clearly the best format for film buffs in the 70s and 80s, and some (like me) even held onto the format well into the 90s, even as DVDs came on the scene. I recall having a few geeky arguments about analog Laserdisc video quality versus the compressed MPEG-2 digital video you'd get from DVDs -- while the Laserdisc was truly better quality in some ways, it was hard to beat DVD for convenience (one tiny disc, dude!), and eventually formats like dual-layer DVD made the argument pointless. Laserdiscs were relegated to the bargain bin of history.

If you're curious about how Laserdiscs worked, here's Don Herbert (known to most of us as Mr. Wizard) explaining the Pioneer Laserdisc system in 1980. It's great stuff -- lots of Mr. Wizard-style props to explain the system, and bits of fun trivia. (For example, Herbert starts his presentation by pointing out that LASER is an acronym, and spelling it out.) Set aside ten minutes for some LASER FACTS:

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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