3DTV Technology: The Nitty Gritty

The good news: Experts say the enabling technologies are sufficiently mature to bring stereoscopic 3DTV to the home.

The bad news: There are at least five content-encoding formats and more than 20 display technologies contending for the lead role.

"They all have their strengths and tradeoffs," said Chris Chinnock, president of Insight Media, which tracks the various display approaches. "The goal is to find something that works with the existing 2-D infrastructure" of production, distribution and display systems, he added. "Some are better for broadcast and others are better for TVs and set-tops," said Chinnock. "How to sort through them all is a little unclear to everyone at this point."

The Society of Motion Picture and Television Engineers has started a process to explore the content-encoding and format approaches. There are five such approaches in play, according to Wendy Aylsworth, vice president of engineering for SMPTE.

Philips' approach, called "auto-stereoscopic 3-D," involves adding metadata to 2-D content, and is the only one of what experts consider the leading methods that includes an option that doesn't require users to wear special glasses.

Other approaches are promoted by less well known companies--DDD Group plc, Real D Cinema, TDVision Systems and Sensio Technologies. All five planned to demo their technologies at an Aug. 19 SMPTE meeting on 3DTV. Dolby Labs and Texas Instruments also planned demos there.

Real D is getting traction in theaters, with deals to serve as many as 5,000 screens in the pipeline, but has yet to announce its direction for home products.

TDVision says its approach can be handled without any new hardware, is compatible with the MPEG infrastructure and can create a single content file that can serve both 2-D and 3-D uses.

Sensio's spatial compression algorithm requires hardware to handle decoding or real-time encoding. However, the company claims the hardware, now in a Xilinx Spartan III FPGA, will not require many transistors or much memory when it is integrated as a block into existing system chips. It showed a prototype 3DTV from SpectronIQ at the Consumer Electronics Show in January, has deals to be used in 50 movie theaters and has 16 movies encoded in its format.

Insight Media has categorized the many display technologies as a tree with three major branches. One branch includes approaches that separate the pixels of the images seen by the left and right eyes in time, another separates the pixels in space and a third places pixels in the same time and space. Most approaches require viewers to wear either active or passive glasses (passive glasses need no electronics or mechanical shutters), but a handful--including approaches demoed by LG, NEC, Philips, Samsung and Toshiba--require no glasses.

The so-called auto-stereoscopic (no-glasses) approaches typically split a large screen HDTV into as many as 20 zones to serve viewers sitting at different angles or distances from the display. The result is a high-def image sliced into multiple VGA-class images.

"They have to trade off a lot of image quality--it's pretty bad," said Chinnock. Long-term glasses-free approaches are a Holy Grail for the industry, but in the short term "it won't work for home movies, but it might be OK for ads or logos," he added.

3DTV will be a niche in the home if it requires special glasses, predicted Eric Kim, general manager of Intel's digital home group. Still, Intel has partnered with Dreamworks on tools that could enhance 3-D cinema and claims it will drive the technology into home and mobile products eventually.

There's still room for improvement. Experts know stereo 3-D can cause viewer eye strain and headaches if the content does not properly handle aspects such as brightness and the convergence of left and right images. However, the industry currently lacks metrics for stereoscopic image quality.

3DTV will force the need for new techniques--and maybe standards--in blocking, scripting, shooting and editing movies and live-action content, said Chinnock. It's a new dimension on many levels.

By Rick Merritt, EE Times