On the transport side, cable operators will have to make some decisions regarding how to encode and distribute 3D video. Initially, operators may start with a polarized 3D system — the same system 3D technology provider RealD is providing to DirecTV to support 3D channels and VOD content for the satellite provider’s service. The advantage is that the polarized format (sometimes also referred to as paneling) will deliver 3D video at roughly the same payload as a standard HD stream, albeit at a slightly lower picture quality compared to the Blu-ray 3D standard. The glasses needed to view the video also are relatively inexpensive, averaging about $20. Eventually, cable-delivered 3D may transition to the new Blu-ray 3D standard, particularly given the direction of TV and DVD manufacturers. But that will require the cable customer to buy the more expensive electric shutter glasses, which range from $100 to $200. But the Blu-ray 3D MVC codec is problematic for cable operators because it requires 50% more bandwidth compared to a standard HD stream. There is a potential variation to MVC that would cut the frame rate in half, but it tends to produce a jerking motion in fast-action sequences. So there is some question whether viewers will find it onerous. The likelihood that the polarized and Blu-ray 3D systems will coexist in the market also presents challenges. If the Blu-ray 3D method is adopted by consumers for DVDs and cable operators and programmers rely on the polarized format, consumers may complain that they are forced to keep both sets of glasses on hand, and may be confused about which set to use with what content. In the modern digital age, two more sophisticated, color-correct methods have emerged. The first, a version of which was used in “Avatar,” uses a trick of light. The dual video footage is encoded at two different polarized light angles (polarizing filters light, blocking all rays except those that enter at a specific angle). The footage is then spliced so that the frames alternate between the left and right eye view, at a frame rate of 120 frames per second. To get the 3D effect, viewers wear special polarized glasses — the right lens is oriented to see one view, and the left is aligned to see the other. At 60 frames per second per eye, the viewer does not notice the change in frames but does see the image in 3D. A second method that has been incorporated into the new Blu-ray 3D standard ratified in December 2009 also involves alternating image frames. It uses the Multiview Video Coding (MVC) codec, an offshoot of the MPEG-4 H.264 Advanced Video Codec now in wide use today and supported by Blu-ray players. MVC also produces a video stream with alternating frames — one for the left eye, one for the right — at a rate of 60 frames per second apiece. In this scheme, the viewer wears a pair of electric-powered shutter glasses that rapidly black out the left and right lenses alternately. An infrared emitter mounted on the 3D HD box synchronizes the timing of the lens movements with the alternating views for the right and left eye. Longer term, developers are working on a system that doesn’t require glasses to view 3D content. Called autostereoscopy, it uses a strategy akin to 3D postcards in creating two image layers and then assigning the two video perspectives to each layer. This can be done with a physical screen called a parallex barrier or by shooting the video using a lenticular lens able vary magnification of parts of the image to create depth. But early results have produced video that is difficult to watch for long stretches of time, with viewers complaining of eye strain and headaches. For that reason, most experts believe 3D video without glasses is several years away. There is also up-conversion from 2D to 3D. Most of today’s up-conversion methods center on duplicating the video frames, then skewing the perspective of the duplicate frames to mimic the stereo image captured by a twin-lens 3D camera. That idea is incorporated into a Toshiba Corp.’s new Cell TV, which is designed to convert 2D images to 3D on the fly. Employing a cluster of rapid-fire 3.2 GHz processors, the TV set can automatically render the stereo frames and deliver them to a viewer wearing shutter viewing glasses. Some critics, however, have branded this form of 3D up-conversion as being substandard to true 3D, particularly with fast-moving scenes, noting that up-converted 2D video tends to make objects appear as if they are always moving away from the viewer. Other observers believe up-conversion may be an adequate short-term fix that’s needed to get a base of 3D content in the market before original production can help fill up libraries.