‘Benefits and Limitations’ Abound in Terrestrial 3D TV, ATSC Report Says

An Advanced TV Systems Committee (ATSC) “planning team” published a request for information on new 3D TV technologies that could be available to terrestrial broadcasters within five years, the organization said Wednesday. The team published an “interim report” on the “benefits and limitations” of known 3D TV transmission technologies and wants information by April 20 about technologies not mentioned in the report, including those under development, so its final report will be as complete as possible, ATSC said.

The team began work last July under the chairmanship of Craig Todd, Dolby Labs’ chief technology officer, studying whether to develop a technical standard for terrestrial 3D TV broadcasts (CED June 18 p1). “There is no doubt that creating and displaying 3D content offers many benefits to increasing the viewer experience and enhancing revenue,” the report said. “The potential downside for broadcasters is that it will require more bandwidth which is scarce and if done improperly, can result in a negative and potential painful experience for their viewers. Clearly technology can solve many of the issues but given the subjective nature of the impact of many of the factors, more information is needed to better understand and implement the services."

There’s a need for studies “to look more closely at the spatial-temporal characteristics of motion in depth and visual discomfort” that can come from viewing 3D, the report said. In particular, “studies are required to look at the impact of long-term viewing that takes into consideration the viewing habits of television owners” who watch TV programming two to four hours a day or more, it said. There’s also more research to be done “to determine the minimum depth information required for the efficient delivery” of 3D TV signals, the report said. “While many studies have been conducted on stereoacuity and the upper limits of stereopsis, almost all the studies have been conducted with simple stimuli under laboratory environments. It would be useful to determine human visual characteristics of depth perception using more complex stimuli that are more attuned to images encountered in typical television programs."

The report said it “documents the benefits and limitations of various 3D data formats and encoding architectures to support the broadcast of 3D services to the home.” All scenarios it discusses “maintain backwards compatibility with existing 2D HD services delivered” via MPEG-2, it said. The report offers “a few general observations” apparent from the use of 3D formats and codecs, including: (1) Using advanced codecs for the additional data that 3D TV requires “is highly beneficial to satisfy bandwidth requirements and maintain high picture quality.” (2) Strong cases can be made for “both transmission scenarios” discussed in the report, including 3D TV programming that’s beamed independent of the 2D signal, and 2D programming that can be “extracted” from the 3D signal.

The planning team foresees “several deployment strategies that would allow enhanced levels of 3D services to be introduced in a compatible manner,” the report says. “For example, one may consider an early introduction of frame-compatible formats for stereo services, then an enhancement of this service to full-resolution stereo, followed by the addition of depth data to support autostereoscopic or multiview displays."

Writing its interim report, the team said, it “uncovered” several issues “not yet fully understood in terms of deployment feasibility.” For example, “the impact on broadcast infrastructure when additional views or new channels of data are introduced is unknown,” the report said. “Also, many of the architectures outlined in this report assume receivers with certain capability such as dual AVC decoders or MPEG-2 and AVC decoders that can operate in a synchronized manner. There may be technical challenges in enabling deployed receivers to correctly decode (and possibly display) the 3D data in some of the considered formats. New receivers could certainly be deployed, but there may be a time lag in the commencement of services."

The planning team hopes and expects that broadcasters will use the interim report “to understand the availability, capabilities and limitations of existing 3D technology as well as technology that is under development,” it said. “This interim report is intended to help facilitate a strategy and requirements towards the deployment of 3D services, and prompt further questions on the technology itself.” The report and RFI likely will be lively topics for discussion at the NAB Show, which opens in about two weeks.