Differential Phosphor Aging And DTS vs. DTS
Dear Gary: As a movie “nut” and audio/video buff, I must say it is almost impossible to keep up with the developments happening in home theatre. Back in ’78-’79 I went on a waiting list to get one of the early “DiscoVision” LaserDisc players when they first went on sale (what a dog!!). Now I have DVD (since ’97), a passable surround system and two weeks ago replaced my 45-inch Pioneer “CinemaWide” RPTV with a 55-inch widescreen Mitsubishi—which, due to budgetary constraints will have to last at least 5 years. This brings me to my first question: Mitsubishi warns owners of 16:9 sets to view programs with “bars” (letterbox at top and bottom or 4:3 gray on the sides) only 15 percent of the time to avoid burn-in. Is this also a concern with emerging technologies such as plasma, DLP and DILA? Granted I bought the unit primarily for DVDs, but still watch cable and an occasional VHS. Second question: My audio gear will decode both Dolby Digital and DTS. There are an increaing number of DVDs with both surround types on one disc, yet certain discs are available in two versions Dolby Digital 5.1 or DTS, and you must choose at the time of purchase. Is the DTS sound on a DTS-only DVD better than the DTS on a disc that has both audio formats? Thank You, and keep up the great work —love your magazine.
Al Myers, amyers@askallied.com
Video Technical Editor Greg Rogers Comments:
The technical term for gradual CRT “burn-in” is differential phosphor aging. Over time the phosphor surface gradually becomes less efficient in converting electron beam current to light output. The brighter it is driven, the faster it ages. So phosphor areas that are used the most, become differentially dimmer than areas with less use. Plasma displays also use phosphor to produce light, so they too are susceptible to “burn-in.” DLP, D-ILA (a reflective LCD technology), and LCD (transmissive) projectors use projection bulbs to produce light. So they do not suffer from this problem. Editor Gary Reber Comments: The bit rate for DTS-only soundtracks on a disc and both DTS and Dolby Digital versions on a disc can be the same and thus are identical in sonic performance. Increasingly, studios are using a 754 kilobits per second data rate for DTS-encoded soundtracks instead of the 1509 kilobits data rate previously used in order to “save” bit space to better accomodiate both a DTS and Dolby Digital soundtrack on the same disc. In sonic terms, the differences between the two DTS data rates is very subtle and virtually impossible to ascertain with certaintly with compared. We are very pleased with the performance of 754 kbps DTS, which still outperforms Dolby Digital, even at 448 kbps, in terms of low level resolution, separation and spatial dimension.
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