On 12/31/2004 11:55 AM, Kyle Rose wrote:
FWIW, I hate interlacing. Interlacing was a technology devised to
overcome a limitation of one kind of display technology and should
have been deprecated with the advent of DTV. Sorry to open THAT can
of worms; just my $0.02. :)
The limitation: bandwidth.
If interlacing is no longer relevant in the age of digital TV, that implies that we now have unlimited bandwidth. However, looking at ATSC high-definition TV, we have two primary modes: 720p ([EMAIL PROTECTED] (fr)/sec and 60fields (fi)/sec) and 1080i ([EMAIL PROTECTED]/sec and 60fi/sec). (Yes, I'm ignoring the 30fr/sec with 30fi/sec, and the 24fr/sec with 24fi/sec progressive modes available for 1080 and 720 resolutions--not to mention the 12 other formats with lower resolutions.)
So, what is the purpose of 1080i? Basically,it allows higher resolution at approximately the same bandwidth. 720p gives 921,600 pixels and 1080i gives 2,073,600 pixels--more than double the pixels of 720p. However both 720p and 1080i take approximately 3MHz bandwidth, compared to 6MHz for NTSC (HDTV takes less bandwidth because of the compression that's possible with the digital signal). So, if 1080i takes half the bandwidth of NTSC, why not make it [EMAIL PROTECTED] Well, the broadcasters feel that the benefits of the progressive format are not worth the cost of the bandwidth--i.e. they would rather be able to transmit twice the number of channels (=2 times as much space for advertisements) in the bandwidth they have available.
Therefore, 1080i yields a much better picture than 720p for "slow-changing" scenes: it is not ideal for sports or other shows that are composed primarily of fast-motion scenes. Given that in most television shows--dramas, comedies, news, etc.--the fast-motion scenes are a very small percentage of the show, 1080i allows much better overall picture quality.
Of course, since nearly all HDTV's on the market have only 1280x720 pixels, the quality benefit is chiefly available to those people using a computer to output to something other than a TV (i.e. high resolution monitors (such as WUXGA) or--for those with a lot of extra cash lying around--a projector with an extremely high optical resolution that can fully resolve 1920x1080, like the Runco DTV-1200 ( http://www.runco.com/OP_PA_dtv1200.html , MSRP $44,995.00)).
But, wait! My TV says it supports 1080i. It does. It accepts a 1080i signal, deinterlaces it, scales it down to 1280x720 pixels, and displays it. Therefore, the TV's available today completely negate the advantage of 1080i (better picture quality) by scaling down to 1280x720 (which can even produce a lower-quality image than an unscaled 720p image).
So, are there any real 1920x1080 TV's out there? I figure if I'm buying an HDTV, I'm not wasting money on a 1280x720 one, but I can't find any 1920x1080 TV's. Toshiba used to have one ( http://www.tacp.toshiba.com/televisions/product.asp?model=57HLX82 , MSRP $8999.99), but now that they've gone exclusively Digital Light Processing (DLP) (instead of the Liquid Crystal on Silicon (LCOS) they used for the 1920x1080 TV), it seems they only have 1280x720. I'm not willing to spend on a projector more than twice what I spent on my car, so the Runco is out of the question. Anyone know of any others?
It looks to me like I may be sticking with SDTV for several more years...
Mike _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
