Arqiva in U.K. Testing Bandwidth-Efficient Terrestrial 3D TV

LONDON -- Arqiva, the private company that runs much of the U.K.’s TV and radio transmission infrastructure, has been secretly testing a bandwidth-efficient technology it calls “Difference 3D” for terrestrial 3D broadcasting, executives told us at a briefing Thursday. Instead of using two channels to simulcast 2D and 3D versions of the same programs, as favored by pay-TV broadcasters such as Sky, Arqiva wants to transmit a single terrestrial 2D channel that can be received by existing equipment, plus a reduced-bandwidth channel that would let a new receiver accommodate a 3D signal for a 3D TV, the executives said.

Frame- or infrastructure-compatible 3D, in which the left- and right-eye images appear side by side in the same picture, “works with existing transmission infrastructure and receivers,” Mike Brooks, Arqiva’s head of technical development, said. “All the viewer needs is a new 3D TV. But the broadcaster has to assign an extra TV channel for the signal. Satellite broadcasters can do this because they have plenty of bandwidth. Terrestrial broadcasters can’t. Sky has led on 3D and the Sky side-by-side method is right for them. They have lots of bandwidth. But we want to start looking at what we need to develop for terrestrial TV."

Arqiva thinks the answer can best be described as “2D plus Something,” Brooks said. He described that “something” as possibly a “depth” signal beamed as part of the terrestrial broadcast. Arqiva also has been “experimenting with a ‘difference’ signal as the ’something,'” he said. “This is the difference between the left and right images. Existing 2D sets just receive the 2D signal and 3D receivers sets use the 2D signal as the left image and use the difference signal to construct the right image. The latest chipsets needed to receive the new DVB T2/MPEG-4 HD broadcasts would only need a firmware upgrade to do this. The STMicro T2 chip already has five processors in it. So the cost of adding 3D is small."

It’s important that “you don’t do anything to upset the 99.99999 percent of viewers with 2D sets,” Brooks said. “We have done bench demos of ‘2D plus Difference’ in our lab and office. We have not yet transmitted signals. That is the next thing. We are talking with the regulator Ofcom and waiting for agreement on a transmitter site -- probably outside London -- where there is some spare bandwidth. We have over 1,100 sites to choose from.”

The technology, also called “Difference 3D,” or “Delta 3D,” is “significantly more efficient than simulcasting” 2D and 3D, which requires two full channels, or 100 percent more bandwidth, Brooks said. It’s hard to quantify the efficiency, he said. But tests done by Dolby Labs on the H.264 MVC codec that’s at the heart of Blu-ray 3D suggest that Difference 3D needs around 60 percent more bandwidth than 2D, he said. “But we have found it can be as little as 20 percent more. It depends on the content. Sport needs more bandwidth. The digital multiplexes already use statistical multiplexing and bit pooling … and the 3D difference signal can be part of the bit pool."

In designing Difference 3D-compatible receivers, “it would be possible to provide a ‘depth control’ option” on the front panel or the remote, Brooks said. “But judging by the way some people set their color controls, I would hate to see what they did with a new depth control. I think we might be digging ourselves a hole."

Difference 3D is no short-term solution for over-the-air 3D terrestrial broadcasts, Brooks said. “I doubt we will see 3D channels on Freeview terrestrial TV,” he said. More likely there will 3D events on 2D existing HD channels. For the 2012 Olympics? That would be an aggressive time scale. Even when the transmission issues have been settled, there is still a lot to be learned about broadcasting 3D. How to present subtitles, for instance. It can be extremely disconcerting if you are looking at the plane of the speaker and subtitles are in a different plane.” In the end, “economics may drive all this, he said. Ultimately it may prove “cheaper than producing separate 2D and 3D versions,” he said.