The Story Behind THX Video Certification—Now With 3D!

Posted by: David Birch-Jones at 4:04 pm, November 10th, 2010

Movie buffs were first introduced to Lucasfilm’s THX theater program back in the day when film sound in your local cinema ranged from just OK to downright mediocre. George Lucas was severely disappointed with the sound quality in theaters back when his original Star Wars and Indiana Jones films were box office champs and seen (and heard) by millions. Having won the first Academy Award for a surround-sound film (Star Wars – A New Hope), Lucasfilm became the bellwether studio for movies with superlative soundtrack design and audio quality.

Once the THX theater program was well underway, Lucas then turned his attention to improving film sound as reproduced in the home, and the Home THX program was born, which included a rigorous set of performance standards along with the mandatory inclusion of proprietary THX audio post-processing and bass management—areas where audio components of the day were lacking. Over the years, as digital audio surround formats became available along with more sophisticated DSP chips, the program expanded to allow both premium and affordable range products.

 

THX Branches Out Into Video Certification

A few years ago, THX launched their video certification program, with certified HD projectors from premium brands Runco and Vidikron, followed by THX-certified flat panel HDTVs from LG, Panasonic and a few others. This past year, THX expanded the video certification program to include additional criteria for 3D, with LG being the first out of the gate with their THX-certified Infinia-series PX950 3D plasma sets (four of the brand new JVC 3D front projectors have just now received THX 3D video certification).

With the newly expanded certification program that includes 3D performance criteria, THX recently invited a handful of reviewers to attend a technical session at their headquarters in San Rafael, California, not far from Lucasfilm’s famed Skywalker Ranch where the THX concept was born. It’s worth noting that THX chairs the 3D@Home Consortium, which includes participants from a broad array of equipment vendors and content creators.

The engineers at THX conducted a PowerPoint presentation that gave an overview of the certification process, which involves numerous testing stages along the way, as well as working with the manufacturers to fine-tune products that are candidate for certification. They also pointed out that since the program began years ago, they’ve not yet had a product submitted to them for certification that yielded a passing grade at the outset—there’s always some (or lots) of fine-tuning needed in order for products to pass.

The array of test gear and the test facility itself at THX is most certainly the envy of video display reviewers anywhere. Instead of relying on commercially available video test pattern generators (some of which can cost in the tens of thousands of dollars), THX chose instead to employ heavy duty computers and develop their own range of test patterns, many of which feature specific scoring metrics that allow reliable repeatability, as opposed to subjective eyeballing, which doesn’t provide the scientific rigor that THX demands

During the introduction to their existing 2D program, the engineers pointed out that they capture no less than 200 data points for each display, examining, among other things, gray scale linearity and color temperature tracking, color gamut accuracy, color tracking, gamma behavior, and a host of other parameters. They also employ, among other reference-grade test gear, a very sophisticated (and correspondingly expensive) Imaging Photometer to gauge a display’s picture uniformity.

While not a digital camera in the conventional sense, the device has an array of imaging sensors that measure a display’s light output at many dozens of points across the screen, to ensure that an object displayed at the screen edge or corner matches, to the closest degree, the same object displayed at center screen. Examples were shown of measured results with both good and bad performing displays, with the poor display example showing marked uniformity problems.

With newly available 3D displays, the revised testing and certification program essentially triples in scope, as the new methodology now demands thrice as many data points—two hundred as before for 2D behavior, plus four hundred additional data points for 3D (two hundred each for left eye and right eye images). It was clear to the invited guests that garnering THX certification is by no means a rubber-stamp type of affair, and is without a doubt the most rigorous third-party testing and certification program out there.

Once the technical orientation was completed, we were graciously invited to attend a private screening of one of the movies on the schedule at the Mill Valley Film Festival, which was going on at the time. We were escorted to a magnificent home in Mill Valley, an upscale, yet charming town a few miles south of San Rafael, where LG and THX (co-sponsors of the film festival) had set up LG’s recently certified flat screen TV and paired it with a THX certified home audio system.

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