Back in the spring, Motorola brought its 3D TV demo to The Cable Show, along with information on set-top and encoding requirements. Here at SCTE Cable-Tec Expo, the demo’s gotten an upgrade. While before Motorola only showed 3D with active shutter glass technology, today it’s got active and passive 3D side by side. What’s the difference? Active 3D uses a transmitter on top of the TV to communicate with a viewer’s 3D glasses, alternately darkening one eye and then the other according to the screen refresh rate. Passive 3D uses half the image resolution for one eye and half for the other along with polarizing filters to create the 3D effect. The glasses are simpler and require no additional information from a separate transmitter.
In the photo from the Motorola demo above, you see active 3D on the left using an IP set-top, and passive 3D on the right using the QAM-based DCX3400. I tested out both, and my highly technical conclusion was that they both look good. The image from the passive 3D display seemed to delineate pretty clearly between foreground and background, which is something I remember from watching “Cloudy with a Chance of Meatballs” in the movie theater. The image from the active 3D display appeared to make the transition between foreground and background a little more gradual. On the other hand, since the content wasn’t the same on both screens, it’s hard to tell how accurate that perception was.
On the bandwidth side of things, I learned for the first time about the role of Multiview Video Coding (MVC) in bitrate requirements. Without going into detail on how MVC works at the moment, when it’s used, 3D TV only requires about 30% more throughput than traditional 2D. That can easily be made up by moving to MPEG-4 compression. Without MVC, 3D apparently takes up about twice the bandwidth of 2D.
More pics from the demo below – glasses and set-tops galore.