In spite of the aggressive marketing aspirations of a few major television industry giants, namely Sony and Panasonic, there are essentially three fundamental tasks remaining before HD 3DTV can become a viable adjunct to the spectrum of consumer electronic products:
1. Determining the psycho-optical parameters necessary to deliver quality 3D HDTV images.
At this time, the Society of Motion Picture and Television Engineers (SMPTE) has the lead in this task. SMPTE is currently developing a “3D Home Master” standard that will purportedly define these parameters in the form of an uncompressed, unencrypted image format derived from a 3D source. Undoubtedly, developing this standard will entail much critical viewing by several “golden eyes,” perhaps even more than was done in the establishing the HDTV standard itself.
2. Developing cost effective HDTV display systems that produce 3D motion images within the SMPTE 3D Home Master parametric standard framework.
Hopefully, the two (SMPTE and CE) display standards can be developed in tandem as many of the same interests and personnel are involved in both. Indeed that is what is happening. Fortunately, but independent of cost variables, all of the present display systems (DLP, LCD, Plasma, LED and OLED) are capable of providing high quality HD 3D images using viewer glasses, either shutter type or polarized. Auto-stereoscopic displays (direct view 3D without glasses), while making progress, continue to suffer from critical viewing angle artifact issues. And the old movie color filter (Blue/Red) anaglyph technique is clearly not acceptable.
Most initial display systems will probably use alternating sub-frame techniques to produce the stereoscopic displays required for HD 3DTV. Lower display cell hold-times now allow over 240Hz refresh rates, producing 1920x1080 pixel 120Hz stereoscopic HDTV displays with minimum optical crosstalk (blur).
3. Implementing a 3D HD signal distribution method within the bandwidth constraints of existing standards.
This task is clearly critical to the expeditious and economical implementation of HD 3DTV. And it must be accomplished without compromising the fidelity of HDTV while maintaining full back compatibility with legacy 2D display systems. Since Blu-ray, DBS (satellite) and Cable distribution bandwidth requirements are less restrictive than for OTA, the former media will probably distribute initial HD 3DTV offerings.
To conserve transmission bandwidth, the most straightforward approach is to multiplex the right and left images to produce a difference (delta) data stream. The delta stream is mixed with additional data that controls some of the “global” aspects of the stereo image generation, such as dynamic parallax correction and timing data. The composite stream is compressed and added to the normal MPEG transport or program frame. With this approach only the left or light HD image is actually transmitted along with the compressed delta/global metadata. The HD 3DTV display system decodes only the main left (or light) image plus the delta stream. The delta data are added to the main image to produce the Right and Left images sequentially displayed in alternate sub-frames. In this manner the 3D transmission and reception/decoding/display systems are fully forward and backward compatible with legacy HD standards.
There is, of course, some bandwidth penalty to be paid for the 3D metadata. An initial estimate of a fully stressed motion HD 3D image estimates that an overhead of approximately one Mb/s would be required. In practice, it is probably considerably less than that. Unfortunately, errors in stereoscopic data translate quickly into viewer eye strain. This is one of the reasons comprehensive empirical viewing data needs to be collected and analyzed before a viable 3DTV standard practice can be established.
More specifics will be known after the 2010 CES, but there is no doubt that the major “players” in the CE industry have a lot riding on HD 3DTV. The winners will be the ones who don’t sacrifice HD for 3D.
Posted by Ed Milbourn, December 15, 2009 8:52 AM
About Ed MilbournAfter graduating from Purdue University with degrees in Electrical Engineering and Industrial Education in 1961 and 1963 respectively, Ed Milbourn joined the RCA Home Entertainment Division in 1963. During his thirty-eight year career with RCA (later GE and Thomson multimedia), Mr. Milbourn held the positions of Field Service Engineer, Manager of Technical Training and Manager of Sales Training. In 1987, he joined Thomson's Product Management group as Manager of Advanced Television Systems Planning, with responsibilities including Digital Television and High Definition Television Product Management. Mr. Milbourn retired from Thomson multimedia in December 2001, and is now a Consumer Electronics Industry consultant.