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Transmitting 3D in a 2D World

Vendors, networks eye new compression techniques 3/12/2010 12:12:00 PM Eastern

Producing 3D high-definition pictures requires new camera
systems that incorporate two lenses—to generate
separate images for the left and right eye—and displaying
them in the living room means buying a new
HDTV set that comes with special glasses to assemble
the 3D images. But delivering 3D HD TV to the home
may not necessitate the complete overhaul of the program
transmission chain that early 3D skeptics had forecast.

That's because networks and pay-TV operators launching 3D HD
in 2010 plan to transmit their video in “frame-compatible” broadcast
formats that are designed to work
within the existing bandwidth for HD
transmission. Such formats use spatial
compression to reduce the horizontal or
vertical resolution of the left- and righteye
images. That is a compromise early
3D programmers can live with, as adopting
“full 3D”—delivering full resolution
to each eye—would require doubling the
current bandwidth used to deliver twodimensional
HD to the home.

More important, frame-compatible
3D formats, which can squeeze the leftand
right-eye images into a normal HD
program stream by interleaving them in
a side-by-side or top-bottom configuration,
among others, are also supported by some existing high-end
satellite and cable set-tops. Such broadcast 3D formats are expected
to be incorporated into the latest version, 1.4a, of the High-Definition Multimedia Interface (HDMI) networking technology that
is commonly used to provide a secure digital connection between
digital TV sets and set-top boxes. Existing late-model set-tops with
an HDMI Version 1.3 connector can receive a software update that
will allow them to connect to new 3D sets with a Version 1.4 connector
to display 3D HD video.

DirecTV, which plans to launch several 3D channels in June, met
with Japanese and Korean set-makers last fall to brief them on its 3D
transmission plans and ensure that its existing MPEG-4 HD set-tops
would work with new 3D TVs. The pay-TV operator demonstrated
live 3D HD satellite broadcasts using frame-compatible 3D, in the
side-by-side interleaved format, at the Consumer Electronics Show in
Las Vegas last month. British pay-TV operator Sky employed a similar
technique to deliver a live 3D soccer broadcast to a handful of pubs
in the U.K. and Ireland two weeks ago. And cable sports giant ESPN
says it will use spatial compression to deliver its new 3D network,
which plans to go live with the 2010 FIFA World Cup in June.

Executives from encoder manufacturers Harmonic, Ericsson,
Motorola and Harris say their products can support frame-compatible
3D, with at most a software upgrade required to optimize
the processing of 3D images. “Our encoder has been used by at
least three major customers, and it works just fine delivering 3D
images all the way through,” says Matthew Goldman, VP of technology
for Ericsson’s TV solutions business (formerly known as
Tandberg Television).

Ericsson’s latest contribution encoder can also support the backhauling
of live 3D images from the field, Goldman adds. A single
CE-xH42 unit can receive left- and-right eye camera feeds, encode
them separately, and send them back to a network in a single
“phase-aligned” stream that ensures the left- and right-eye images
stay in sync when decoded.

DirecTV, which uses a mix of Harmonic and Ericsson MPEG-
4 encoders to deliver its HD programming, won’t need any new
hardware to transmit 3D in the 720p, 1080i or 1080p/24 frame-persecond
formats, according to CTO Romulo Pontual. But the company,
which showed 1080p/24 3D at
CES, has licensed technology from
3D display specialist RealD and is
working with encoder vendors to
optimize their software.

“It’s some of the preprocessing
[capabilities] they don’t have,” Pontual
says. “Part of that is done at the
program producer, and part of it is
done at DirecTV.”

Pontual says DirecTV will likely
use a slightly higher bitrate for 3D
than it currently uses for its normal
MPEG-4 HD streams, but he
wouldn’t give a specifi c number. He
did dismiss the notion that fitting 3D
in the same bitrate as 2D HD, by using the side-by-side interleaved
format, means cutting the horizontal resolution in half.

“That’s absolutely not true,” he says. “It would only be half if you
were transmitting identical left- and right-eye images. 3D already
gives me a gain, as every odd pixel to one eye is representing an
even pixel to the other one. If you’re smart in how you’re picking
pixels, you can get a very high horizontal resolution.”

The technology behind frame-compatible 3D isn’t exactly
new. Montreal-based Sensio Technologies has been specializing
in spatial compression techniques for 3D video for a decade, and
unveiled its first product for high-end home theater systems in
2003. It now sells its proprietary decoding technology in its own
3D chips and also licenses it to other manufacturers. The company
announced at CES deals to license its 3D video processing
technology to set-makers Vizio and ViewSonic and home-theater
technology provider THX, and it has worked with ESPN and the
NBA on early 3D tests.

Sensio’s implementation of spatial compression technology creates
a “virtually lossless” end picture for the viewer, says Richard
LaBerge, the company’s executive VP and chief marketing officer,
even though either horizontal or vertical resolution must be sacrificed to deliver 3D down an existing 2D pipe. As LaBerge puts it:
“There’s a way to play with each pixel.”

 

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