Article Sections
TV: High Definition
17 October 2009 - 3:37pm
From 2006
Currently resolutions of Standard TV are:
576 Lines for PAL and Secam
480 lines for NTSC
The old VCD (Video CD and CDi, not SVCD, Super Video CD) uses only 320 x 240 lines or 384 x 288 lines and simply repeats the lines on the odd and even fields to give 480 or 576 lines.
Analog TV can be produced by filtering "square pixel" 640x 480 for NTSC and 768 x 576 for PAL/SECAM.
DVDs can use either 704 or 720 horizontal pixels for the NTSC or PAL lines.
HD is a big step for USA / JAPAN in the the 30% lower resolution NTSC and typically in USA much, much bigger TV screen. They really need it.
But really it is of limited value on 576 line on screens below 36", which unlike USA is majority of TV sets in Europe.
The 720 line progressive and 1080interlace where chosen as compromise resolutions for CRTs. No one will be using CRT for HD, the two resolutions should have been 960p (default USA) and 1152p (Europe) and then Ordinary definition would be perfect on a fixed pixel LCD, Plasma or DLP. The 480 line or 576 line SD is degraded badly on 720, 768 or 1080 line native pixels.
[Added and updated 2010]
Example: Choosing an HDTV
The typical Irish living area the viewing distance is about 7' to 9' (approximately 2m to 3m).
480 is USA / Japan only. 720p is practically only broadcast in USA, not Europe.
Saorview (Irish DTT ) is all 576i 25fps and 1080i 25fps.
The main 4 channels will gradually migrate to HDTV (1080i) during 2011 to 2014.
At 2.5m (slightly more than 8ft) you may want a 48" or larger TV. If you watch much 2.35:1 cinematic content on upscalled DVD or BD, 48" is an absolute minimum.
Typical recommended sizes for viewing distances (Note 720 is not broadcast in UK or Ireland so can be ignored.
Generally pick next biggest size of closest viewing distance
576 720 1080 32" 8' 6' 4' 37" 10' 7' 5' 40" 10.5' 8' 5' 42" 11' 8' 5.5' 46" 12' 9' 6' 50" 13' 10' 6.5' 52" 13.5' 10' 7' 65" 17' 13' 8.5'
From http://www.hdtvtest.co.uk/Article/How-Far-Should-I-Sit.php Highlighted is for SD or HD at about 9' (2.75m)
If you never watch films (many wider screen than WS TV thus need bigger screen) and you don't bother with glasses (but maybe should) and mostly watch Soaps and News, then 37" is perfect. If you are going to watch HD (1080i) then 37" is too small for 9ft. You'd not notice much increase in quality with HD.
To Cover all content from 576i SD TV to Cinematic 2.35:1 WS on Bluray, a projector with Zoom lens is perfection as that gives 36" to 72" 
For mix of mostly 576i with some HD 1080i and no big BD (bluray) collection, then 48" is a perfect compromise.
For Mostly 1080i HDTV broadcast and load of Bluray, then 56" @ 9ft. You would find the "recommended" 60" to 65" on typical website calculators for 1080 @ 9ft a bit dominating in room and far too big for non-HD content.
The screen should have HDMI (HD) and SCART (regular TV) inputs. Native resolution (pixels) 1920 x 1080. Avoid "HD Ready"
Tuner for aerial should be DVB-T2 (UK and Ireland) or DVB-T (Ireland only) and support MPEG4, H.264, AAC and MHEG5. In the UK it should have a "Freeview HD" logo and in Ireland a "Saorview" Logo. A "Freeview HD" set should work in Ireland, with HD, but a "Saorview" only set with only DVB-T and no DVB-T2 will only do basic non-HD Freeview in UK.
Other Options
PVR (recording features via an Internal HDD).
DVB-S2 second Tuner input for Satellite Dish LNB feed.
A PVR Setbox is a better solution if you regularly record.
Do we need bigger TV Sets? Why bother with HDTV
well.. if you had money you bought a 26" even in 1970s
A 32" to 37" Widescreen is needed to replace a 26" or 28" 4:3 set.
The whole reason for developing HD is because in Japan and USA they had bigger screens (even 3 tube CRT rear projection) and NTSC Color 525 lines (480 visible) looks terrible on 36" 4:3 never mind 56"!
Ever wondered why HD is really stupid 1080 (visible) lines?
Quote:
Japan had the earliest working [Colour] HDTV system, with design efforts going back to 1979. The country began broadcasting analog HDTV signals in the late 1980s using an interlaced resolution of 1035 or 1080 active lines (1035i) or 1125 total lines.The Japanese system, developed by NHK Science and Technical Research Laboratories (STRL) in the 1980s, employed filtering tricks to reduce the original source signal to decrease bandwidth utilization. MUSE was marketed as "Hi-Vision" by NHK.
* Japanese broadcast engineers immediately rejected conventional vestigial sideband broadcasting for well-founded technical reasons.
* It was decided early on that MUSE would be a satellite broadcast format as Japan economically supports satellite broadcasting.
The German 1940s and French 1950s HDTV was only monochrome. Not Colour.
see http://en.wikipedia.org/wiki/Analog_HDTV#Multiple_sub-nyquist_sampling_Encoding_system_.28MUSE.29
Quote:
MUSE would be 1035i (or 1080i, hence the origin of less than ideal 1080 for digital HDTV. 960p60 for USA and 1152i25 for Europe and 1152p48 worldwide would be better).
Normal eyesight is such that in Europe the 30% better resolution (for 576i vs 480i) means there is little value in HD on a 32" 16:9 screen (Widescreen) at typical viewing distance.
