Japan tests digital TV quality

Japan tests digital TV qualityInitial results suggest 480-line progressive transmissions offer superior quality to 480 interlaced ones. Roy Rubenstein. Japan is evaluating TV broadcasts which uses a subset of the digital formats being proposed by the US digital TV industry. Some 11 companies – including Matsushita – are taking part in the trial involving the transmission of 480-line progressive (480p) scanned frames to over 50 locations in Japan. According to Dr Takafumi Ueno, a senior engineer at Matsushita, ‘subjective’ results from the trial suggest that 480p transmissions offer superior picture quality compared to 480i (interlaced) ones. The digital TV trials are set for completion late next year with a commercial broadcast satellite service beginning in 2000. Five formats will be transmitted: 480i/p, 720p and the high definition 1,080i/p. These are similar to the digital TV services adopted in the US, except that there 18 formats are available. Matsushita has already demonstrated its digital system for both 480p and the 18-format standard at the US consumer electronics show earlier this year. It is also developing a set-top box design for the US and Japanese markets, and is using its Media Core Processor for the MPEG-2 audio and video decoding. Too many standards?
The adopting of 18 formats, all MPEG-2 based, in the US is a result of compromises made to get some form of agreement among all interested parties.
Each digital format is optimised for transmitting some form of existing format over the minimum possible bandwidth while retaining appropriate image quality. For instance, there is one for sending wide-screen movies, which have a high aspect ratio, are filmed at 24 frame/s and are scanned best progressively. Another is for sending studio video from existing video equipment which produces 30 frame/s interlaced low aspect ratio images.
The US regulatory body, the FCC, has not shown strong leadership and the final number of US formats could easily rise and then be whittled down by market forces. The consumer loses because the chosen set-top box has to be more complex (expensive) to deal with the proposed 18 standards, and may not even be able to deal with one of the eventual winners. It is possible to specify a sub-set of the 18 or more standards which can deal with all formats, although at the expense of bandwidth efficiency. This is what is being done in Japan with its five formats. Plasma on display…. Shown are the internals of Panasonic’s 42in. plasma display. The display is based on technology from the US firm Plasmaco, acquired by Matsushita Electric Industrial in 1996. Matsushita claims such performance parameters for its display as brightness of 450Cd/m2, a contrast ratio of 400:1 and a relatively high colour temperature of 9,300K. Although a lower temperature could be used resulting in a brighter picture, Matsushita argues the picture quality would be compromised. A prototype 50in 16:9 plasma display panel was shown at the Panasonic Industry Exhibition ’98. Matsushita expects to produce the 50in. panel in volume next year.


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