Cable-TV operators and their suppliers are stepping slowly into the new era of stereo 3-D television, but it could take years before they can handle full high definition content.
Some cable networks are broadcasting handling a growing schedule of 3-D events while vendors test interim standards using firmware upgrades to support partial high def signals. Set-top boxes, TVs and back-end encoders will need a new generation of video and interface chips to carry stereo-3D broadcasts in full high definition.
“It’s coming in steps,” said David Grubb, chief technology officer at set-top maker Motorola Home. “First we’re making 3-D as compatible as possible with existing video infrastructure,” he said.
“We’ve worked in past year on sorting out agreements on 3-D formats, making the consumer experience easy so when they tune into a 3-D channel the TV automatically switches to right mode and presenting 2-D graphics like closed captions and program guides in 3-D space,” he said.
CableLabs, the R&D consortium of the cable-TV industry, expects to finish interoperability testing of its so-called frame-compatible approach in about six months. “We have lab prototypes of encoders and set-tops and we’ve seen end-to-end demos,” said David Broberg, vice president of consumer video technology at CableLabs.
The group released in early September its specification for encoding stereo 3-D signals. It defines metadata to let set-tops identify 3-D content and its format type and pass that information to a 3-D capable TV over an HDMI version 1.4a interface.
That capability will let TV’s automatically decode the signal. Today consumers need to manually select the correct 3-D mode on the TV after they tune into a 3-D channel.
Today CableLabs and HDMI 1.4a support three 3-D formats for packing signals for two eyes into one existing video channel—separate top and bottom formats for 720-progressive 60 Hz and 1080p 24 Hz signals and a side-by-side format for 1080-interlaced content. The result is a signal presented to the TV for decoding at something less than a full high definition resolution.
The metadata supplies information to a graphics engine about how to find and decode 2-D graphics data in the formats.
Some cable operators have already been supporting limited 3-D broadcasts in an ad hoc fashion while engineers are testing the interim frame-compatible solution. Cablevision carried the first 3-D broadcast in March—a live Rangers vs. Islanders hockey game from Madison Square Garden.
Since then other cable networks have aired 3-D broadcasts of the Masters golf tournament in April, the soccer World Cup in June and NASCAR races in July. Comcast is creating a video on demand library of stereo 3-D titles and ESPN will begin weekly 3-D broadcasts this fall, said Broberg.
“I still consider it kind of an experimental, early-adopter stage–the number of people who buy these 3-D sets is small and the number who understand how to use them is even smaller,” said Broberg. “When we get to 24×7 3-D broadcasts is hard to say, but I suspect when it happens there will be a lot of repetition in programming,” he said.
Next-generation set-tops and encoders will have to adopt new video and interface chips to pass through full high definition versions of left and right eye video signals. The chips will require standards still being debated. We have seen a high number of cable manufactures releasing hdmi cabled for 3D, we can see a sell in the uk under the brand cablesson 3d 10m hdmi cable
“There are a number of proposals—some proprietary and some through standards groups like MPEG–for how to deal with a migration to full resolution delivery, but right now there are more questions than answers,” said Broberg.
For example, the MPEG multi-view coding specification could be used for high def 3-D. However, MVC was designed to support multiple camera angles, not stereo 3-D, and it might not be compatible with the interim so-called frame compatible spec.
Today’s 1080-progressive 24 Hz Blu-ray signals or 1280×720 video games at 60 Hz can max out the bit rate available on today’s fastest 150 MHz HDMI chips, said Broberg.
Supporting a full 1080p 60 Hz signal for left and right eyes in a 3-D broadcast would require 300 MHz HDMI chips.
“Silicon Image [a lead developer of HDMI chips] said that’s a couple years away,” said Broberg.
Meanwhile cable TV operators are using a variety of bit rates to support 3-D broadcasts depending on factors such as available bandwidth and whether the content is fast action. The broadcast services will not be as crisp as content from 3-D enabled Blu-ray players which use a frame-packing technique that can deliver a full HD signal for both eyes.
“There’s a lot of variable quality because we are at the very beginning of the learning curve,” said Broberg
Next-generation set-tops ultimately will need upgraded graphics to handle stereo-3D program guides. Developers are demonstrating such apps at trade shows, but they are a low priority