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Why is there not 1 standard frame rate for hi-def tv?

Discussion in 'TVs' started by Rob20, Jan 9, 2005.

  1. Rob20

    Rob20
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    It seems to me like a missed oportunity. I assumed that when the world upgraded their tvs to hi-definition, they'd use the oportunity to create 1 standard for the world. i.e. 720p60, 1080i 60 and 1080p60. If we're all going to have to buy new sets for hi-def, and USA/JAP already have high def at 60fps, it makes sense to use that as a standard. Hi-def UK tvs will probably run at both 50 and 60 hz so older tv shows could still be brodcast at 50hz. Newer shows filmed in hi-def would be 60p from the start. In this way. all hi-def shows would be compatible worldwide. Why then will we have 2 seperate hi-def systems, 50hz in the UK, 60hz Jap/USA? Makes no sense to me.

    Also, why can't modern tvs run at the correct 24p/48p for films? or 78p/92p even for a more stable picture? :confused:
     
  2. Dutch

    Dutch
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    Well this is what the EBU concluded regarding this subject:

    One of the fundamental questions considered by the EBU Project Group was whether Europe
    should change to a 60 Hz system for the sake of commonality with the 60 Hz world.
    It certainly would be attractive to have a common worldwide standard and there would be benefits in
    using 60 Hz in terms of motion portrayal; and, for some types of display, large area flicker would be
    reduced. Weighed against this is the higher bitrate that an equivalent 60 Hz system would need.
    On balance, it is difficult to make the case in a Europe where there is serious frequency congestion
    for what may be unnecessarily high bitrates. It is also true that those countries that have already
    started HD have a plurality of standards, so even adoption of a 60 Hz picture rate would not bring a
    common worldwide standard. If might have been feasible if there were universal adoption of a
    single progressive 60 Hz system, but we have been told by the 60 Hz world that this is impossible to
    expect.


    So there you go. Seems a shame really.

    Steve
     
  3. Rob20

    Rob20
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    Shame. Still, in the future we'll probably access thousands of hi-def channels via Ultra fast BB connections or eqivelent.

    Why isn't it a problem in USA/JAP?
     
  4. Quickbeam

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    It's not a problem in the USA and Japan because they already had a 60Hz scanning rate in NTSC.;)

    Besides the bandwidth issue quoted by Dutch, I can think of other reasons why 60Hz HD is not favoured in Europe. One is simulcasting. While downconverting 50Hz HD to 576i50/PAL is relatively straightforward and looks good - better than native SDTV in fact - downconverting 60Hz HD to 50Hz SD is much more difficult: you would end up with SD that looked like a juddery NTSC to PAL conversion.

    It's possible that some 60Hz HD content may be rebroadcast without being converted to 50Hz. According to the European HDTV Forum's HDTV-Ready label, "in order to guarantee a minimum interoperability with US and Japanese rebroadcasts all the formats in Table 1 [720p/1080i at 50, 59.94 and 60Hz] shall be supported. Please note that switching between satellite services may imply a change in the picture format conveyed over the input interface (e.g. from 1080i25 to 1080i30). The display needs to be capable of re-synchronising accordingly."

    As for correct speed 24 frame playback, I doubt we'll ever see that on channels that simulcast in SD due to the difficulty of padding 24 frames to 25. However, 720p24 and 1080p24 are recognised HD formats supported by HDMI, and next-gen DVDs are expected to use the 1080p24 format, so you could in theory broadcast movies in the 1080p24 format on a premium HD movie channel such as Sky Movies HD. What happens in practice may differ.
     
  5. Stephen Neal

    Stephen Neal
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    As Quickbeam has pointed out - the fact that we have 50Hz SD services is a major reason to stay with 50Hz for HD.

    Can you imagine running simulcast versions of BBC One, containing a mix of HD and SD material when the SD stuff was 50Hz but the HD 60Hz? You'd end up with 60Hz HD material converted to 50Hz for SD viewing, and 50Hz SD upconverted to 60Hz for HD viewing (or worse all the 50Hz SD stuff would be converted to 60Hz for a single HD network feed, which would then be downconverted back to 50Hz for SD transmission - 2 conversion in the SD chain?). Yuck. Don't even start on the difficulties running 50Hz and 60Hz timecode in the same transmission area (drop frame or non drop frame)

    Can you imagine the nightmares of covering events where other European broadcasters want 50Hz SD feeds of isolated cameras, but you are covering the event in 60Hz HD?

    Downconversion of 50Hz HD to 50Hz SD is cheap and simple. Conversion from 60Hz to 50Hz - whether HD to SD, SD to SD or HD to HD is never trivial, nor is it high quality or cheap.

    Oh - and don't forget that a huge amount of US HDTV production isn't at 50Hz anyway - it as 24Hz progressive... Arguably we get a better deal by showing 24Hz progressive sped up a little at 50Hz 2:2 pulldown. In the US they have to use 3:2 pulldown to get from 24 to 60 - with all the motion disturbance that entails.

    I think that to go 60Hz in Europe would have been a completely mad decision - after all - how much US 60Hz (as opposed to US 24Hz) material do we actually watch over here? Almost all US drama and high-end sit com is 24Hz - only their sports, talk shows and cheap sit com and drama (as well as news) is 60Hz...
     
  6. Nick_UK

    Nick_UK
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    .... at the moment ! Produced in significant numbers, they could be. Look at the VHS machine - when it first appeared, it cost £750, which is about £2000 at today's money. Now they're £50.

    Sticking to 50Hz will sentence Europe to being "also ran's" because 60Hz is the biggest market, and manufacturers will always concentrate on that. Europeans will have to be satisfied with the crumbs that fall from the table.
     
  7. Stephen Neal

    Stephen Neal
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    Not the same thing though - standards converters between 50Hz and 60Hz - even those costing £100,000s are not capable of perfect conversions (SD or HD). Sure you can now buy a £300 SD 525 to 625 converter - doesn't make it watchable (it isn't).

    They've been making standards converters (optical then digital) since well before the advent of the VHS VCR - and they are still not perfect or cheap. Broadcast kit (like field rate converters) are never going to be hit by the economies of scale in the same way as consumer bits of kit (you aren't going to sell millions of 1080/60 to 576/50 converters to broadcasters - so they won't get cheap - but they would need to buy enough of them for it to be expensive both in purchase costs and space to house them)

    The HD converters used by NBC to convert 1080/50i to 1080/60i for the Olympics were the state of the art - and they were far from perfect.

    The bottom line is that if you are running an SD service at 50Hz you'd have to be certifiable to move to an HD service based on 60Hz. You are making a decision that reduces SD quality - and also introducing the 3:2 pulldown nightmare potentially - something we've managed to avoid with 50Hz.

    Err - except that China, the former Soviet Union, most of Africa, Australia and New Zealand are all 50Hz as well.

    China is moving to 50Hz HD for the Beijing Olympics, and isn't an insignificant market, don't forget that they are PAL 50 domestically... I think globally - if you include China and the former Soviet Union - you'll find 60Hz is the minority standard not 50. (Even parts of South America run 50Hz - though sometimes bizarre variants - like PAL N) I think if you are after low-cost displays - China producing 50Hz HD sets for domestic consumption might be in our favour?

    Currently 60Hz regions are ahead in HD origination (Japan, US, Korea at 60 vs Australia and HD1 in Europe at 50) - but as I said, much of the US stuff isn't actually at 60 - it is at 24 (Almost all HD drama is 24fps film or 24p video). Arguably 50Hz is more compatible with 24fps stuff than 60Hz (2:2 with 4% speedup is visually a better solution than 3:2 pulldown)
     
  8. Nick_UK

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    Errr... don't think so ! The number of TV's per head is much higher in the USA and Japan than it is in China and the former USSR. Just add the TV ownership of the USA, Canada and Japan together, and I think that is more than the rest of the world. Not to mention:

    Antilles, Bahamas, Barbados, Belize, Bermuda, Bolivia, Brazil, Cambodia, Chile
    Colombia, Costa Rica, Cuba, Dominican Rep., Ecuador, El Salvador, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Peru, Philippines, Puerto Rico, Samoa, South Korea, Taiwan, Venezuela and the Virgin Islands :cool:
     
  9. beeblebrox12

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    Yeah. Maybe on 50Hz set after doing 24->60->50 fps conversion, or on an PC, where they still can't get the 3:2 pulldown right. A standard $100 DVD player on a standard 60Hz US TV will exhibit no detectable judder. While the 4% speedup is nasty anyway you look at it. I remember back in the 70's the audio hi-fi standards for casette players stated that the tape speedup should not exceed 2%; and 30 years later, with much more advanced technology, for both audio and video 4% is acceptable?
     
  10. Master Rahl

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    Eh? It is? I don't think so. HD cameras don't just store 24 frames a second.
     
  11. Stephen Neal

    Stephen Neal
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    You might not see 3:2 pulldown - I certainly do and don't like it. The obvious motion judder it introduces on camera movement is pretty objectionable to me, though I'm not used to watching it, so maybe am more sensitive to it.

    I have a number of region 1 DVDs - and those sourced from film, with 3:2 pulldown, are noticably different to region 2 film sourced 2:2 pulldown transfers.

    I agree the 4% speed change isn't perfect - but I prefer 2:2 visually to 3:2 - as the motion isn't distorted by one film frame being weighted more than the other.
     
  12. Stephen Neal

    Stephen Neal
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    Err - sorry Master Rahl - many high-end HD cameras can operate at the following rates :

    1080/24p, 1080/25p, 1080/30p, 1080/50i and 1080/60i, or 720/50p or 720/60p (if they run at both resolutions)

    Where HD video has replaced film it is most commonly run in 24p mode - as that replicates "the film" look, with the lower frame rate. I'm not saying HD cameras ONLY run at 24p - but where HD cameras have replaced film (say on shows like Enterprise?) they are run at 24p rather than 60i. It is an aesthetic rather than technical issue. (Rockface, which was a BBC/US co-production, was shot at 25p - our "film for TV" frame rate - for this reason. Previously it would have been shot on film at 25fps)

    Where they have replaced SD video cameras (say on sport or chat shows) they are often running at 60i or 60p, for that "fluid" "video" look.
     

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