To: DiViT who wrote (29432 ) 2/12/1998 4:56:00 PM From: John Rieman Read Replies (1) | Respond to of 50808
Japan sets Digital TV standards. Encoders need to get better............................................techweb.cmp.com Posted: 3:00 p.m. EST, 2/12/98 Japan sets broadcast-satellite digital-TV standards By Yoshiko Hara TOKYO -- Japan has nailed down standards for the delivery of digital TV via broadcast satellite,specifying six video formats with MPEG-2 Advanced Audio Coding (AAC). Service is expected to start in Japan around the year 2000. The Telecommunication Technology Council (TTC), an advisory body for the Ministry of Posts and Telecommunications (MPT) submitted the final recommendation for broadcast-satellite (BS) digital-TV broadcasting earlier this week. The video formats to be used are: 1,080 vertical lines x 1,920 pixels (16:9) at both 60i and 60p picture rate; 720 lines x 1,280 pixels (16:9) at 60p; and 480 lines x 720 pixels at 60i (both 16:9 and 4:3) and 60p (16:9). Unlike the Advanced Television System Committee (ATSC) specifications in the United States, 30p and 24p picture rates are not included, thus reducing the number of formats. Of these six formats, 720p and 1,080p were included with reservations, because they haven't yet been put through a field experiment. The 1,080p format must also be tested to see whether a single transponder can send two 1,080p channels. An MPT official, Masato Iwasaki, said that "720p has not been verified in field experiments. If it is proved to be no problem through field experiments, it will be officially added." In satellite broadcasting, one transponder sends two HDTV channels. Iwasaki, deputy director of the Digital Broadcasting System Development Division at MPT's Broadcasting Bureau, said, "To send two 1,080p channels with one transponder is difficult unless compression technology makes further progress. It is expected to take several years. But these formats are Japan's BS digital-TV specifications that broadcasters can choose." MPEG-2 Audio (AAC) became an ISO/IEC standard last April. "We believe that Japan is the first to adopt MPEG-2 Audio (AAC)," said Iwasaki. It has no compatibility with current MPEG-2 Audio (backward compatible), but has twofold compression efficiency. With MPEG-2 Audio (AAC), CD-quality stereo sound can be transmitted at 128 kbits/second. Based on the previously agreed presumption that BS digital broadcasting will be devoted mainly to HDTV programs, the council defined the specifications so that two HDTV channels can be transmitted by one satellite transponder for the first time ever. To provide services such as data broadcasting in addition to HDTV programs, a wider bandwidth is desirable. The recommendation listed three possible bandwidths--27 MHz, the same as current satellite broadcasting; 33 MHz and 34.5 MHz. Even with the 27-MHz width, the rate will be 39 Mbits/s, allowing two channels of 18-Mbit/s HDTV programs. "For better picture quality, 34.5-MHz width is desirable," said Iwasaki of MPT. If 34.5 MHz width can be used, the maximum bit rate reaches 51 Mbits/s with TC8PSK (Trellis-coding eight-phase shift keying), a high density transmission coding. Japan will negotiate at the International Telecommunication Union to expand the assigned bandwidth. Two broadcasters in Japan--DirecTV and PerfecTV--already deliver digital-satellite TV-broadcasting service. But these services use communication satellites and send 480i standard-definition programs.