Gary Merson, a long-time writer about conumer electronics and the pubisher of HDTV Insider on the web, recently completely a study revealing that many mfgrs have been bobbing 1080i signals--that is, upconverting each 540-line field to a display's native resolution (720p, 768p,1080i, or 1080p) rather than buffering the two 540-line fields to construct a proper 1080p frame before releasing them to the TV screen. The result can be a shortfall in the detail that consumers expected to get, even though they may not have noticed it (Merson claims that he can see the dfference). The situation has apparently improved with the 2005 sets, but 2004 was rife with this sort of bobbing. As you might expect, 1080p sets that go this route are particularly at fault, since consumers often bought them to convert 1080i signals, not 540 vertical lines, to 1080p (Sony's LCoS sets don't bob). The companies that failed the test consistently were Sharp and LG; the mixed bags were Sony, Panasonic,and Samsung (all of its DLPs). JVC, Hitachi, Pioneer, and Toshiba had no failures (except for one out-sourced Toshiba). Faroudja/Genesis and PixelWorks "admitted" that some of their chipsets worked in this way. A few companies have disputed Merson's findings for certain sets--Sony and LG, for example.

The seriousness of this problem is up for grabs. I certainly don't think that it falls squarely into the category of false advertising. After all, scaling and deinterlacing are almost as much art as exact science. But I don't think that it is just a semantic problem either, or a choice between equal methods. A 1080i signal is not simply two independent 540-line signals; it is one coherent unit. To divide it up into discrete pieces the easier to deal with it is to distort it. Merson's study does indicate that cost is a factor; the sets that don't bob are more expensive. At the very least, mfgs should reveal which kind of scaling/ deinterlacing option they use. After all, we know the difference between TI's HD2, HD3, and HD4 chips. We should be equally aware of the disadvantages, as well as any advantages (like cost), of the bobbing chips.

Ed

Anyway, more detail on the study is available at hdtvinsider.com, and in this installlment of The Perfect Vision. I'm not usre whether TPV's website, AVguide.com, contains the info.