Like NTSC and DTV before it, the holy grail of 3-D TV is a scheme that enables broadcasters to send a single transmission that can be displayed by both new (HD with 3-D) and legacy (SD) DTV sets. This backward-compatible strategy saves broadcasters bandwidth (money) and helps to smooth consumers’ transition from one transmission standard to another.
Several different types of frame-compatible methods have been experimented with (and deployed commercially) that display two sides of a stereoscopic image simultaneously, but each has suffered from some type of image degradation due to the fact that they are basically halving or partially reducing the vertical or horizontal resolution of the source image. There's side by side, top and bottom (over/under) and quincunx (checkerboard).
In Italy, they will soon begin experimenting with another way of sending and displaying 3-D signals while simultaneously adding an HD stream to the multiplex. Quartarete TV, a digital terrestrial TV broadcaster serving the Piedmont (northwestern) region of Italy, will begin offering a separate 3-D channel by the end of the year along with its HD channel.
Quartarete TV, working in tandem with the Italy-based Sisvel Group, will use the 3D Tile Format to deliver HD and 3-D content as two 720 elements (right and left eye) within a single 1080p/50 HD signal, via the DVB-T broadcast standard, which those involved said offers a higher quality than current frame-compatible solutions. Consumers with 3-D TVs can watch in stereoscopic 3-D (with glasses), while consumers with traditional HDTV sets will see the same content in 2-D.
The 3D Tile Format was developed by the Sisvel Group (and inventors Paolo D'Amato and Giovanni Ballocca) and is being developed with the CSP-Innovazione nelle ICT, a Piedmont region research and development company that works with emerging technologies to productize them. The 3D Tile Format is a series of algorithms that splits a 3-D image into three parts that are compressed in H.264 and then transmitted along with a single HD frame.
The reconstructed left and right pictures keep their original resolution and are not be affected by the imbalance of the vertical and horizontal resolution, according to Davide Ferri, manager of business development at Sisvel Technology. The layout of the images within the 3D Tile Format, together with standard-compliant technologies, seamlessly allows the decoding of 2-D video from the 3-D transmission in the set-top box, where they are reassembled and displayed for viewing with active-shutter glasses.
Ferri said the 3D Tile Format represents a breakthrough for terrestrial broadcasters like those in the U.S. looking for a more cost-effective way to offer 3-D channels. The key is having 10Mb/s of bandwidth to do it.
“It’s possible to put all of the 720p frames inside a 1080p/50 frame and maintain the original quality without artifacts and some of the problems some of the other systems have experienced,” he said.
Ferri explained that the decoding and display of the 3D Tile Format material might be implemented in two different ways. The first is to receive the video output from the H.264 decoder and to reassemble the two views by cutting and pasting the three parts of the second view. This approach requires an increase of the memory available for storing the output video. The second approach is to recompose the stereo pair during the decoding of the H.264 format. In this case, the decoded macroblocks will have to be arranged in an order that is different from the one determined by the raster scanning of the compressed image, and that might be, as an example, described in a suitable lookup table.
“In any case, unless the decoding of the format is included in the LCD panel management system, an external decoder is required to decode and present the stereoscopic format,” Ferri said.
Ferri said his company estimates that there are roughly 40,000 3-D TV sets sold across the entire country. “After Christmas season, we expect to see more sets in the public,” he said, “but now is a good time to experiment and figure out how to do this correctly.”
He also said that the only way that terrestrial broadcasters, of which there are some 400 regional providers in Italy, will be able to practically distribute 3-D is to send 3-D and HD as a single channel. Other broadcasters in Italy are now offering HD and 3-D as separate channels, but they are finding it very costly to do so.
The city of Turin, where the companies involved held a press conference to announce the experimental 3-D broadcasts Nov. 30, was also the origination site of the first commercial transmission of radio (1930) and TV (1949) services in Italy.