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What happened to 1250 HDTV?

Discussion in 'Televisions' started by Wayne Moule, Dec 4, 2004.

  1. Wayne Moule

    Wayne Moule
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    The BBC were testing and talking about doubling the current PAL 625 to 1250 HD years ago. Now we seem to be going to get 720 or 1080.

    Are we also talking line resolution here?
     
  2. Chris Muriel

    Chris Muriel
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    The 1250 line idea has been ditched , or rather overtaken by real standards like 1080 (i and p) and 720 as defined in the USA ATSC standard amongst other places.
    It has gone the same way as HD-MAC on satellite , to the ideas graveyard in the sky.
    It might have got somewhere if the BBC had pursued it and invested heavily enough in it years ago.


    Chris Muriel, Manchester.
     
  3. hornydragon

    hornydragon
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    1250 is a supported res of HDMI but i think the extra res is data not picture like 625 is 576 lines of video.... and is a version of 1080 perhaps 1080p
     
  4. Wayne Moule

    Wayne Moule
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    So is either 720 or 1080 HDTV going to be actual line resolution over 576 lines of PAL SD?
     
  5. Dutch

    Dutch
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    Yes.
    720p = 750p including non-visible lines
    1080i = 1125i including non-visible lines.
     
  6. Wayne Moule

    Wayne Moule
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    Thanks, but what do you mean by non-visible lines?
     
  7. Chris Muriel

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    They are lines that are set to an amplitude that is below black level (so they aren't visible) and contain data, e.g. teletext and some types of copy protection info).

    Chris Muriel, Manchester.
     
  8. Wayne Moule

    Wayne Moule
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    And Dolby Digital/DTS sound?
     
  9. jgrg

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    Yes, but I don't think you need this in digital sources. This is a trick to hide extra information, such as teletext in analogue broadcasts. In digital sources you just flag each piece of the datastream as video, sound, or data. So there aren't any "lines" that aren't shown.

    James
     
  10. NinjaShredder

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    I'll just say that for 1080i (1125i) component video (analog), the extra lines are still there. Obviously you don't need teletext coming from your component video source (ie upscaling DVD player, HD sat box). The extra lines are used for the TV to sync to, as the EXACT refresh rate is determined by the source signal, not the TV.
     
  11. rscott4563

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    1250 can be used to describe 1080i @ 50Hz, this is accepted by my Panasonic, the other lines will be as mentioned previously, non visible..

    So 1250 hasn't disappeared it's just not described often as 1250..

    Ryan
     
  12. Stephen Neal

    Stephen Neal
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    The 1250 line standard was proposed as a European HD standard in the late 80s and early 90s, and was developed as part of the Eureaka 1250 project. The US had a similar proposal using 1050 lines.

    Both of these standards refer to the total number of lines used in the analogue video signal used to feed a monitor (including the lines that were used for vertical sync purposes), these days it is more common to quote the number of active lines, as this is what is broadcast and recorded using digital techniques.

    Initially there was 1250 (2x625) which had 1150-1152 active lines, 1125 (the Japanese HiVision/MUSE system) which had 1035-1050 active lines and 1050 (2x525) which had 960-972 active lines.

    The original HD standards often involved broadcasting an HD signal using an SD channel (HD MAC did this by effectively interlacing static picture information over 4 or more fields), so it made sense to stick to simple multiples of the SD line count. (It also made it much easier to build cheap line-based scalers to convert from 625 to 1250 or vice versa)

    When digital TV systems became available for both production and transmission - and analogue or analogue+digital assistance HD broadcaststandards began to look a bit of a white elephant - the need to stick with 1250 or 1050 (with their links to 625 and 525) became less.

    The bulk of commercial HD kit actually made when digital HD was being developed was for the 1125 (1030-1050 active) Japanese standard - as they actually ran a broadcast service in Japan.

    Rather than introduce a new, 4th standard, the 1080i (active) standard was effectively created by reducing the number of blanking lines in the 1125 (total) / 1030-1050i (active) Japanese standard. In fact some early US HD stuff was actually 1050 not 1080 with a few lines of black at the top and bottom!

    Effectively 1250 HD is a dead format - apart from where it is used internally in display devices to line-double a 625 total/576 active SD signal.

    As for the comments about why there are different active and total lines this is to allow CRT displays to fly back to the top of the screen from the bottom when they have reached the end of a field (frame if progressive) - and also allow signalling of where the field/frame starts.

    The video in blanking on analogue signal isn't always at a level below black - indeed only the sync parts should be. Teletext and other data in blanking (such as Vertical Interval Time Code - as used in broadcast kit) in analogue video signals is often peak white - you don't see it because the TV doesn't display these lines - it blanks the spot as it flys back.

    In broadcast digital video signals used to interconnect bits of kit, the beginning and end of active video is signalled by specific protected levels (usually 0 and 255 in 8 bit video are reserved for signalling purposes) and the horizontal and vertical blanking periods can contain data of pretty much any value (not just sub-black as others have posted)

    A digital TV signal AS broadcast, will only encode the active video information - so 576 rather than 625 lines for example, for carriage as digital video. The data signals that would ordinarily be carried as part of the video signal in blanking on analogue are just carried as separate digital streams via a digital TV transmission scheme.
     
  13. jgrg

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    Great post! Very informative.

    James
     
  14. CKNA

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    Actually Japanese never worked on digital HD until ATSC digital standard was pretty much set. Analog MUSE was actually one of HD systems proposed to FCC for use in US. It was eliminated in a first round as FCC said that US is going digital.

    MUSE system always has 1035 lines visible.
     
  15. CKNA

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    I am not sure where you got this info but all US HD was 1080 from the begining. There was some stuff that was converted from Japanese MUSE that had 1050 but it was not native US HD. Unless of course you are talking about analog experimental HD from the 80's.

    I have to say though, that I have never seen any recordings. Rumor has it that some Los Angeles Olympics were shot by ABC in 1050i format but I never found any confirmation of that.
     
  16. Stephen Neal

    Stephen Neal
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    You are misreading or misunderstanding my posts. Japan had MUSE analogue transmission - and HiVision production gear, including some digital production gear (their digital 1" open-reel DVTRS looked scary!)

    Whilst the US were the first to have a digital HDTV BROADCAST standard, there were others using digital TV PRODUCTION standards to create material for analogue transmission, which for HD has real advantages. (Try running HD analogue component around a broadcast facility and you'll know what I mean...)

    My point was that when the US was developing a digital HD transmission system, the only large market for HD production gear was Japan (where digital and analogue production gear was sold for production for MUSE transmission) It therefore made sense for the US to use, or tweak, the Japanese production standard to work with their proposed transmission standard rather than create an entirely new one. ISTR that they basically "square pixelled" the HiVision standard - using neat binary friendly values.

    You are right that MUSE transmission was 1035 lines, however the HiVision production standard allowed for up to 1050 I believe (hence my 1035/1050 posts) It was relatively simple to tweak the blanking/syncs part of the standard to increase the active picture line count to 1080, whilst keeping the line/field rate the same.

    I think you are merging production and broadcast standards - partially because in the days of composite you often used the same (NTSC or PAL) for both. However HiVision and MUSE weren't the same thing - though they were linked obviously by dint of HiVision kit being used to produce for MUSE transmission.

    For info there was quite a small but significant HD production market in the US, using 1125/1035i HiVision gear before the ATSC standard was set. There was also a small but significant 1125/60i market in Europe as well. For a while there were a number of 1250/50 and 1125/60 HD production trucks knocking around - I remember that the BBC used both during the 90s. (1125/60 for productions that NHK wanted in HD - 1250/60 for hiqh quality arts events that would merit high quality archiving, and mastering for laser disc release)

    The LA 1984 Olympic Gamess were covered in HD - and I'm pretty certain this was using 1125/1035 Japanese kit - that is certainly the format I saw the footage in in 1990 - and I don't think it had been converted from 1050/960i (and I don't think there was any 1050/960i stuff around for production that early?)

    The 1992 Albertville Winter and Barcelona Summer games were both extensively covered using 1250/50 (I watched the HD MAC transmissions in 16:9 SD at the time) Similarly Wimbledon was covered in both 1250/50 (experimentally) and 1125/60 (for broadcast) in the early 90s.

    1050/60 never really was applied as widely AIUI - though it was used in lab tests and formed parts of many analogue HD and a few digital HD transmission schemes that were proposed.
     
  17. Stephen Neal

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    Yep - the 1050/60 stuff was the experimental stuff happening around the time of the 1250/50 stuff in Europe, and the 1125/60 stuff in Japan. The Japanese took this the furthest and made a decent amount of 1125/60 (1035-1050/60i active) production gear (VTRs, Cameras, Mixers etc.) to allow them to produce a full HD broadcast service using MUSE analogue.

    BTS made tubed cameras (KCH1000s?) that could be switched between 1050 and 1250 - and these were used for the late 80s analogue production experiments in the US and Europe. In the UK they were also used, along with a few first generation 1250/50 CCD HD cameras, for digital production experiments as well (using 4 625/50 D1 DVTRs to record) Both the CCD and tubed cameras weren't really production models - they were still close to being bespoke devices for experimental services - in comparison to the Japanese HiVision kit that was being produced for conventional production environments.

    AIUI 1050 was proposed initially by GI as part of their HD Digital scheme (which kind of put the kybosh on the US adopting an analogue scheme) though the Grand Alliance eventually settled on 1920x1080, and 1920x1080 has since become a common image format for all field/frame rates (24p,25p,30i,50i,60i)

    Of course the big advantage of a common image format, is that for the first time it has been possible to produce multi-standard HD cameras that can run at both 50 and 60 Hz field/frame rates- previously the 576 vs 480-483 line standard differences meant this was impossible with conventional CCD cameras.
     
  18. CKNA

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    Thanks for explanation. It makes it much clearer what you meant in previous post.
     
  19. AML

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    You guys are HARDCORE :D

    I live in japan, and the HD standard is still reffered to as Hi Vision.
    If you buy a digital tuner as i have, and conect it to a decent TV (I have a Fujitsu Plasma) You get a really amazing picture with a channel called "BS Hi"

    Its a totaly sepparate channel from any other broadcast and has to be the most amazing picture Ive ever seen.

    Japanese TV is funny in that they have 3 different TV base channels/stations.

    1 is for japanese local TV station like TV Tokyo and Fuji TV.
    there are about 10 viewable channels to choose from.

    Next is the BS station that broadcasts 1000 channels but at the moment only the BS Hi channel is active.

    Im guessin that the ammount of channels they show there will increase over time.

    Last is the Cable TV channel/network that broadcasts poor quality (in my opinion) yet digital channels. About 100 viewable channels.

    Im not sure about the resolution but i think it is as you guys mentioned 1125i for BS Hi and same for the japanese channels i mentioned. Cable is only about 525i.

    Just thought you might find this interesting!
     

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