Transmitting 3D in a 2D World
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
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 right-eye 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
two-dimensional HD to the home.
More important, frame-compatible 3D formats, which can squeeze the left- and
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-per-second 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
specific 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
Chris Lennon, a member of Harris Broadcast's CTO
group, says that 3D purists have generally dismissed frame-compatible 3D.
Instead, they have promoted the full-resolution approach, which is how 3D
movies will be delivered on Blu-ray optical discs; or another, more complicated
technique called "2D plus delta" in which full resolution is sent to
the left eye, and additional depth information for the right eye is sent
alongside it and reconciled by the receiver. But the conversations about
frame-compatible 3D quickly turned pragmatic as programmers and operators got
closer to 3D deployment.
"People said, Ã¢â‚¬ËœIt's OK, it looks pretty good and most consumers will be
pretty happy with that,'" Lennon says. "I think frame-compatible
helps establish 3D television to begin with. If there's a good business there,
and it seems to be taking off, then perhaps it will evolve to 2D plus delta or
two full streams going to folks."
Bob Wilson, VP and general manager of Motorola's networked video solutions
business, agrees that frame-compatible 3D is the only way to launch 3D to
existing set-tops. But he thinks the industry will eventually shift to
delivering 3D with full 1080-line-progressive/60 frame-per-second images to
each eye. Besides new set-tops, that will also require a reworking of the live
production infrastructure, as 1080p/60 cameras are just becoming available.
"They'll have to go half-res per eye for most events, but I think the
high-end, top-end stuff will move to 1080p/60 for competitive reasons," Wilson says. "Just
like Ã¢â‚¬Ëœfull HD,' you'll start hearing about Ã¢â‚¬Ëœfull 3D TV.' The fidelity of
the image is something people will start competing on."
David Price, VP of business development for Harmonic, also believes that
1080p/60 is the eventual endgame for 3D. But he predicts that a significant
portion of operators will stick with frame-compatible 3D for the next decade.
That's why Price, who also serves as VP of the MPEG Industry Forum, hopes that
manufacturers like Harmonic and Motorola can convince networks and operators to
agree on using just one or two of the various frame-compatible formats.
"We at Harmonic, and other manufacturers, love it when there's just one
goalpost to aim for," Price says. "It's in our interest to try to get
this cohesion as early as possible."
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