HDTV TECH

A Look Inside THX Testing
THX display testing is broken into two primary categories: Front of Screen and Video Signal Processing. Due to limited space, we have chosen to describe just a few of the THX tests.

Front-of-Screen Performance Tests:
White and Black Luminance of Full Screen:
Ensures maximum brightness.

Checkerboard Luminance and Contrast:
Clarity and detail in varying luminances.

Gamut and Colors of Full Screen:
Maximum color-rendering capability.

Gray Scale of Full Screen and Determination of Gamma:
Proper playback of luminance levels.

Maximum Display Resolution as Determined From Contrast Modulation:
Can the display really make a good image at the rated resolution?

Uniformity and Color of White, Black, Dark Gray:
Ensures that the picture level is the same everywhere on the screen.

Convergence (for multi-imager systems only):
The colors are aligned properly for good detail reproduction.

Video-Signal-Processing Tests:
Deinterlacing—Bob, Weave: Since most broadcast signals are interlaced (e.g., 480i, 1080i), it is critical that the image is deinterlaced properly for clean, defect-free images.

Motion Compensation: Motion adds complexity to the deinterlacing process and causes additional artifacts if not treated correctly.

Cadence Detection and Correction:
Motion pictures and other media are produced at varying frame rates, and it is critical to properly convert them to the display's frame rate to minimize visual artifacts.

Jaggies: Lines and borders can appear disjointed, reducing image smoothness and clarity.

Contouring: Occurs mainly in scenes of gently changing areas of contrast, such as a cloudy sky; viewers see blocks where there shouldn't be any.

Sharpness-Filter Ringing: A processor's sharpness filter can add noise around sharp image transitions, usually around text, reducing readability.

Noise Reduction: Tests how well the processor removes noise from the picture while distinguishing the noise from real picture data.

Image Break-Up: Sometimes occurs in scenes of very fast-moving, highly detailed images and appears as a garbled image.

Some of the more tech-savvy readers might claim that certain of these measurements will favor one technology over another. This is true, especially when you consider that THX plans to certify front projectors, plasmas, LCDs, and future display technologies. So, how will THX get around this with one spec?

According to Patrick Dunn, director of display technology at THX, there will be various acceptable thresholds for the differing technologies. "We can't expect all of the displays to behave the same way, since many are fundamentally different," says Dunn. "The biggest differences show up in the device-performance tests, as opposed to the signal-processing tests, because most display technologies share similar signal-processing circuits."

THX Certification, Coming to a Display Near You
Display manufacturers all claim high quality and performance, but the THX certification is designed to create a single performance benchmark. With the specifications outlined in the Certified Display program, THX hopes to educate and empower consumers like you to sift through self-proclaimed "best-in-class" marketing tactics to select a display that best fits your needs. But will it work?

Thus far, big brands such as Runco, Vidikron, and TiVo (the Series 3 HD is the first THX-certified DVR) have all jumped at the opportunity to certify new HD video products. The common vision of bringing cinema-quality experiences to the home, coupled with THX's track record of assuring high-impact audio and visual playback, made it a no-brainer for these early adopters to seek certification before THX publicly announced the program.

"The THX team has developed performance parameters that all premium display manufacturers should aspire to achieve," says Bob Hana, president of Runco. "A lot of the THX certification

is built on in-depth knowledge of how movies are created in the studio and presented in the theater. Not many companies understand both the content production and playback sides of the business like THX does."

As the adoption of HDTVs hits critical mass in the coming years, many analysts believe that the premium brands will need to find ways to stand out in the crowd. THX certification might just provide them with a means to do that. We will all be watching.