Two-Phase 3D Strategy Poses Big Questions for Cable Ops

Making 3D out of 2D on a very big screen at Cowboy Stadium.

Making 3D out of 2D on a very big screen at Cowboy Stadium.

December 21, 2009 – The Blu-ray Disc Association’s mid-December adoption of a 3D standard underscores the challenges confronted by bandwidth-constrained service providers, who must somehow get in the 3D game without throwing the consumer and supplier markets into a state of confusion.

The cable industry, for example, is pursuing 3D specifications through CableLabs in a two-step process that foresees eventual migration to the high-quality format used in the new Blu-ray standard. But, as described by David Broberg, vice president of consumer video technology at CableLabs, the industry is likely to settle on an interim step that will fall short of delivering the level of quality slated for new 3D Blu-ray players expected to enter the market as early as the second quarter.

“It’s a walk-before-you-run kind of phase,” Broberg says. “It gives the cable industry a chance to test the market, understand the implications of stereoscopic television, and then, as the technology becomes available in new silicon and new set-top boxes, we can begin to deploy the higher performance system.”

But Broberg readily acknowledges the interim format, whatever it turns out to be, will not measure up to the approach taken by Blu-ray. “There is a compromise in performance by doing that, so that’s why we’re looking at the longer term solution,” he says.

The Blu-ray 3D specification calls for encoding 3D video using the Multiview Video Coding (MVC) codec, an extension to the H.264 Advanced Video Coding (AVC) codec currently supported by all Blu-ray Disc players. MPEG4-MVC compresses both left and right eye views in the stereoscopic stream, with the result that rather than needing to double the bit rate to accommodate delivery of a full-resolution picture to each eye, there’s only a 50 percent bandwidth overhead penalty with no sacrifice in resolution.

In contrast, the “paneling” stereoscopic technique that is likely to be adopted in CableLabs’ first-phase specifications does not require any more bandwidth than a 2D HDTV signal. “You’re using the same amount of channel bandwidth capacity, but you’re trading off the spatial detail for the depth,” Broberg explains. “Technically we can get the stereoscopic through the plant without changing anything.”

In all stereoscopic 3D systems the idea is to deliver picture information separately to each eye on an alternating frame-by-frame basis, which results in a perception of dimensionality when the brain combines the images. The paneling approaches vary the polarization of the picture signal on an alternating frame basis, where the total information contained in a 1080p HDTV signal is split in half on either the vertical or the horizontal axis.

There’s also been some thought given to using the alternating full-resolution frame approach adopted by Blu-ray but at half the frame rate so as to avoid the bandwidth penalty. In other words, where the Blu-ray system and new 3D TVs supporting this approach operate at 120 Hertz supporting 120 frames per second, or 60 frames per stereoscopic stream, an interim cable version would cut the frame rate in half to deliver a full resolution signal to each eye within the allotted bandwidth.

But there’s a drawback to this approach having to do with the jerkiness of motion in fast-action sequences. “If you use the same amount of bandwidth and you use an alternating frame, you’re reducing the temporal resolution,” Broberg explains. “You’re affecting the ability to display motion.”

Whichever approach is taken the interim phase will allow cable operators to deliver 3D through existing digital set-tops to anyone who has a 3D TV set. But the question is, how much room will cable operators and other service providers have to maneuver in trying to seed the market with an alternative format if Blu-ray 3D takes off?

As Victor Matsuda, chairman of the Blu-ray Disc Association’s Global Promotions Committee, notes, there’s every reason to believe Blu-ray 3D will ramp quickly in light of the box office success of 3D and the surging penetration rate of Blu-ray. “In 2009 we saw Blu-ray firmly establish itself as the most rapidly adopted packaged media format ever introduced,” Matsuda says.

At the same time, he adds, “movie goers have shown an overwhelming preference for 3D when presented with the option to see a theatrical release in either 3D or 2D. We believe this demand for 3D content will carry over into the home now that we have, in Blu-ray Disc, a medium that can deliver a quality full HD 3D experience to the living room.”

Research firm Futuresource Consulting, which correctly forecast the recession wouldn’t thwart consumer acceptance of a true HD format for DVD, now predicts Blu-ray 3D will be a strong factor in ongoing success of the next-generation DVD player. “The quality and experience of High Definition via Blu-ray disc is unparalleled, and for those consumers not yet convinced by the HD experience, 3D will be another key selling point and a highly persuasive reason to upgrade,” says Jim Bottoms, a director at Futuresource.

With 3D-capable HDTV sets from Panasonic, Sony, LG Electronics and others now entering the market pegged to the same 3D process adopted by Blu-ray, there’s likely to be a high-end 3D market developing in that format even before the CableLabs first-phase 3D approach is adopted and implemented by cable operators. “Our research shows that 3D-enabled BD players will be available in Q2 next year to support the major push on 3D TVs that will start at CES and build throughout the year,” Bottoms says. “Further interest will be driven by owners of [Sony] PS3 consoles, which will be able to play Blu-ray 3D content.”

The good news for service providers is that the move to an interim phase of 3D will allow them to deliver TV programming as well as movies in 3D, which will provide a 3D content component for 3D TV set owners otherwise not available, whether or not they own 3D Blu-ray players. But this strategy will impose on service providers the challenge of persuading consumers to use the types of 3D glasses needed for the lower-quality format as the Blu-ray contingent is promoting the shutter glasses required for their format.

The Blu-ray system requires relatively expensive shutter glasses, which respond to signals from infrared emitters on the TV or Blu-ray box to alternatively block the view of each eye as the frame meant for the other eye appears on screen. The glasses used in the alternative polarization-based panel approaches don’t require active electronics and therefore are much cheaper. Presently, with the lowest priced shutter glasses tagged at about $150 versus a few dollars or less for polarized glasses, marketing of glasses could become a point of intense competition. For example, consumer electronics manufacturers might bundle the shutter glasses “free” with TVs and disc players while polarized glasses are offered for purchase at retail or at no cost by service providers as part of a 3D service package.

Just what the broadcast or special programming component beyond movies will be for a cable 3D service is still unknown. “I think the programmers are ultimately going to set the timeline for when there’s enough content to justify an impact on cable subscribers,” Broberg says. “Is it just one episode a month or is it a full channel that has something all day long? And how much [VOD] quantity is it going to take?”

A big driver for service providers could be big ticket events such as the Super Bowl, Olympics, concerts and boxing matches, Broberg adds. “Things like that you’re not getting from Hollywood,” he notes. “And with VOD and pay-per-view kinds of services there’s also an opportunity to create a special event around 3D.”

The 3D service option could get a big boost from new technologies that can turn traditional 2D content into pseudo 3D on the fly in real time (see ScreenPlays November issue, p. 8). One supplier of such technology, HDlogix, demonstrated the capabilities in dramatic fashion at Cowboys Stadium in Dallas during a football game between the Cowboys and the San Diego Chargers on December 13.

Some 80,000 fans in attendance were given 3D glasses upon entering the stadium. Beginning with the second half kickoff, the video coverage of the game displayed on the enormous center-hung screen was converted from high definition 2D to 3D, enabling fans to view both live action and instant replays in 3D.

Such capabilities raise intriguing questions as to what will define 3D in the eyes of most consumers. Because the HDlogix platform can be used with any 3D format, service providers could opt to translate 2D content for viewing in the active-glasses mode used with Blu-ray, sacrificing some resolution owing to the bandwidth compromise, or follow the polarized approach with its bandwidth compromise intact. And, with Blu-ray beginning to penetrate, will any pseudo-3D approach prove acceptable to consumers?

So far, demonstrations of 3D delivered over a 2D HDTV bandwidth stream have been seemed less than optimal when displayed next to the full resolution dual stream stereoscopic system used in Blu-ray. But while the polarization method applied within existing bandwidth allocations essentially cuts the total resolution of the received picture in half, the perceived effect isn’t as bad as one might expect, especially if there’s no opportunity for a side-by-side comparison, as will be the case in most households.

“I think there are some psychological factors when you see a 3D image that are tradeoffs just like color and monochromatic viewing,” Broberg says. “There are different eye characteristics and brain characteristics that allow you to use bandwidth efficiently. When you see the added depth you tend not to notice as much about the detail. In other words, the detail is very critical when you’re viewing a 2D picture. It may not be quite as critical when you’re seeing a 3D picture, because you’re so involved in the immersive experience.”

Many recent demonstrations involving the paneled approach with polarization have produced TV pictures where the 3D depth effect results in a flatness of the images at different depth levels – a sort of cardboard cutout effect that eliminates the roundness and continuity of images from the near to the distant horizon. But Broberg says the severity of the effect depends on how the picture is squeezed.

“There are different ways in which you can create that spatial multiplexing,” he explains. “When you squeeze the picture side by side and pack them that way, you’re actually compromising the horizontal resolution of the image. And with the stereoscopic picture the horizontal resolution defines the degree of depth you have in the picture. So as you reduce the resolution you are creating a more granular depth perspective.

“But when you divide the picture vertically and squeeze it vertically,” he continues, “you lose the vertical resolution, but you don’t compromise the depth at all. You do lose a little vertical resolution, but you have not compromised at all in depth quality. So there are tradeoffs to the different techniques.”

There are also ways to get around the cardboarding effect and other drawbacks by making adjustments in the production phase, which is part of the standards-setting process for 3D underway at the Society of Motion Picture and Television Engineers (SMPTE). SMPTE is “looking at the mastering techniques and best practices for the production and development of [3D],” Broberg says. “There’s a lot to be learned from the production side.

“For example,” he adds, “a telephoto lens tends to distort the image in stereoscopic imagery in a way that creates this very stepped cardboard cutout kind of effect. If you use a wider angle lens and get closer to the subject you don’t have that effect.”

There are also ways to improve the 3D performance in a bandwidth-constrained environment by setting specifications that would vary how techniques are applied according to what type of content is being delivered. “We’re testing with 720p 60 frames per second on some of the content,” Broberg notes. “We’re also testing some other content with 1080p 24. So one has higher spatial resolution but lower frame rates, and the other has higher frame rate but lower spatial resolution.

“Bandwidth is about the same,” he continues, “but it depends on the content. We don’t necessarily want to pick a single mode that works for everything. We want to understand what the tradeoffs are and what the optimum for each type of content would be.”

CableLabs is working closely with other standards bodies as it works through these issues. “I’m personally chairing the SCTE (Society of Cable Telecommunications Engineers) 3D ad hoc group, which is developing a standard for the cable industry, participating on the CEA standards group for 3D, and I’m also participating on the SMPTE standards group for 3D,” Broberg says.

While CableLabs is pursuing the interim approach with every intention of developing specifications that create the most optimal experience possible, operators could avoid the interim step without incurring a bandwidth penalty were they to decide to deliver their 3D content over their DOCSIS 3.0 IP streams rather than sticking to the traditional MPEG-2 digital TV format. Indeed, the need to deliver a high-quality 3D service matching Blu-ray and eliminating the dueling glasses hassles could become a major inducement to IPTV migration on the part of cable operators.

As CableLabs CEO Paul Liao notes, IP and MPEG-4 go hand in hand. While MPEG-2 was a big leap forward compared to the bandwidth consumed by analog, it’s still “wasteful compared to the way we could do it if we went to a really all-digital IP world,” Liao says.

Thus, by delivering 3D in H.264 with the full-resolution approach taken by Blu-ray operators would actually be consuming less bandwidth per stream than they do using MPEG-2 to deliver 2D HDTV streams. “With H.264 and MVC (Multiview Video Coding) it’s going to be maybe one and a half times the standard bandwidth requirement [for HD delivered in MPEG-4],” he observes. “So I think there’s a path forward on that.”

It may be necessary to take the interim 3D approach over the existing MPEG-2 delivery framework, Liao says. But, he adds, “What we’d really like to do is be able to provide a premier experience.”