I was extremely curious about the article by Gary Merson in the December 2005 issue of Perfect Vision Magazine that let us know that a large number of HDTVs being sold today throw away half of the 1080 lines sent by the broadcasters and present a scaled 540p picture on the display.
Just to review what is at issue: Some manufacturers opt to display the 540-line half-resolution fields sequentially and individually rather than spend more money on new chips that weave the broadcast’s two 540-line fields into a single full-resolution, 1,080-line frame before the scaling. While this theoretically will improve the temporal resolution of live interlaced video while still having better than 480 line spatial resolution (although not much in terms of lines) it does effectively present a 1920×540 maximum spatial resolution. Since there are still 1920 pixels per line the resulting picture will still be much better than SD, but will actually fall short of the ATSC and CEA specification for HDTV. ATSC requiring 1280×720 or 1920×1080 pixels for HDTV and CEA requiring a minimum of 720 lines only.ï¿½
The testing was done using a SMPTE 133 test pattern at 1080i. This puts alternating black and white lines on the screen with a total of 540 black lines and 540 white lines. To pass the test, there should be no flicker. The test fails if the screen flickers due to the alternating black and white lines being shown each frame.
Many of the forums that have discussed this subject seem to imply, or readers have implied, that this report was true for the new 1080p panels. I found this to be quite surprising that the manufacturers would cheap out on the deinterlace chips when they are selling a more expensive 1080p HDTV. So in order to try to get to the bottom of this I purchased and downloaded the December 2005 issue of Perfect Vision Magazine to see what Gary said for myself. Turns out that the majority of the sets tested were not 1080p, but rather 720p or 768p panels.
Further to emphasize the report is not yet talking about the current models this excerpt:
I plan to test many 2005 models and brands in August and beyond, as they become available (especially the latest 1080p displays) and will report the results here.
In the table summary provided in the article there are not any model numbers to tell us exactly what sets failed the test, but manufacturers were listed along with the quantity of failed/passed units. Another excerpt from the article:
Set-makers with more than one model tested fell into three distinct categories: manufacturers whose sets passed across the board (JVC, Hitachi, Pioneer, and Toshibaâ€”though one 44″ Toshiba-manufactured DLP model, sourced from another company, failed); manufacturers that had some sets pass and others fail (Sony, Panasonic, and Samsung); and manufacturers whose sample sets all failed (Sharp and LG). Engineering spokespersons for processor-makers PixelWorks and Genesis said their latest chipsets, which only recently became available, properly deinterlace 1080i signals, but none of the 2004 models containing motion component. Only one display passed the static test and failed the motion testâ€”the Sharp LC45GD6U. Passing the motion test is necessary to view all television programming at full resolution. All of Samsungâ€™s flat-panel displays (LCD and plasma) passed, including the firmâ€™s 1080p LCD set, while all of the companyâ€™s DLP rear projectors failed.
While I’m not surprised that many of the 720/768p sets would fail this test in the 2004 models, I was surprised at the 1080p models, at least the few mentioned. The Sharp model that passed the static test and failed the motion test is not surprising, however, as many processors will have a chip that will switch between the film mode and video modes where the basically weave the fields in the film mode, but bob the fields in the video mode in an attempt to preserve the temporal resolution of fast motion interlaced video.
This subject will be worth watching as the newer models come out to be sure when you pony up the big bucks for a 1080p TV, you get all of the picture you should. Also for the 720/768p sets as well.
Edit: Unfortunately the download link that was originally here is no longer available.