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Will HD Football be better on non HD TV

Discussion in 'General TV Discussions Forum' started by milkmanchris, Sep 10, 2005.

  1. milkmanchris

    milkmanchris
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    I have read many threads and none seem to answer the question really.

    I have a Panny TH42PE50 and although the pq is very good most of the time, if i connected SKY HD via the component would the quality be better.

    I realise that the screen would 'downscale' the resolution to match the screens, but would this better pq than i am getting now?

    Or is a case of posting in 6 months time and asking someone with the same set up if its better?

    Cheers Guys
     
  2. Stephen Neal

    Stephen Neal
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    It is likely that Sky HD will look better downconverted to SD than Sky SD broadcasts containing downconverted HD pictures. This is because compression artefacts present on the HD signal should be reduced in visibility by the downconversion process AFTER reception, whereas the SD artefacts on the SD broadcasts will be at the SD level and more visible.

    It is also likely that Sky will be aiming to maximise the HD picture quality - at least initially - so may not over compress HD material as much as SD... Well we can hope.

    The one caveat is that the downconversion to SD from HD performed in receiver may not be high quality - and may nullify the other benefits of downconversion at home rather than at broadcaster.

    The only reason to use component rather than RGB SCART connections is if the colourimetry of the HD broadcasts is different to SD (in the US they use a different set of colour paramaters to the SD Y=0.59G + 0.3R + 0.11B standard). It may be that some screens expect SD chroma standard on SCART but HD component on SD component inputs - but it is also possible that the Sky receiver may correctly handle the chroma space conversion...
     
  3. Rimmer

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    You need to check whether your panel can accept 720p50 and 1080i50.

    If it does, the HD picture should look very good when downconverted to 852 x 480p. I was very impressed the quality of an HD demo I saw recently on a 480p plasma in PC world. It was actually better than some of the demos I have seen on higher resolution screens.

    If the Panny doesn't accept either HD format the improvement in picture quality will be minimal; very little point in getting Sky HD in my opinion. Although the panel has only 480 lines of resolution, progressive scanning means that the visible resolution can be significantly higher than interlaced PAL - but you won't see the benefit unless the panel accepts the full quality HD signal and downscales internally.
     
  4. milkmanchris

    milkmanchris
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    Well thanks for clearing that one up Rimmer.

    According to the manual with the plasma can accept both those signals and display them through component.
     
  5. avinitski

    avinitski
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    but even though the manual says it can accept and display the signal can it actually display it at the original resolution?

    just like in my thread here i found out my TV can accept a HD signal but will not fully show it
     
  6. Stephen Neal

    Stephen Neal
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    Is that the case?

    I thought the resolution of interlaced PAL was pretty close to that of 480 lines progressive (i.e. around 75-80% of the interlaced line count - 430-460 lines - not hugely less than 480) - which was one reason that 576 line plasmas weren't developed (why have two panels when one will do?)

    Therefore a 576i signal exploits pretty much the maximum resolution of a 480p panel... It certainly isn't massively lower resolution than a 480p signal.

    A 480p panel won't display the full vertical resolution of a 576p signal.

    There could be an advantage in straight 720/50p to 480/50p conversion with no 576/50i in the way - but I don't think the resolution gain is likely to be huge - though the clarity of capture on moving images may be noticable.
     
  7. binbag

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    I read the heck out of the 'official' 4805 thread over at AVSforum. The Americans rave about HD images over this 852x480 projector (I know NTSC is worse than PAL so the improvement would be subjectively greater).
     
  8. Rimmer

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    I don't agree that a 576i signal exploits the full resolution of a 480p plasma.

    Perhaps the most obvious improvement offered by an HD downconversion to 480p is in the colour resolution. PAL has a colour resolution of 360 x 288i. With 720p the colour resolution rises to 640 x 360p, while 1080i has a maximum colour resolution of 960 x 540i. When HD signals are downconverted to 852 x 480p nearly all the HD colour resolution will be retained, close to RGB 4:4:4.

    In digital TV the horizontal and vertical resolution of an interlaced signal is taken to be the number of scan lines multiplied by the Extended Kell Factor, which is usually quoted as 0.7. So a 720 x 576i signal would be expected to have an effective resolution of around 500 x 400 pixels. This doesn't take into account noise reduction and MPEG-2 compression which can reduce the resolution by a further 20%. (As an interesting side note, if our 720 x 576i broadcasts only deliver about 500 pixels horizontally, why is it that 544 x 576i broadcasts look noticeably worse? A good example of this is E4 (544) vs E4+1 (720) on Freeview. My guess is that the drop in colour resolution, increase in noise reduction and lower bit rate are to blame, rather than the reduction in luminance resolution itself).

    Don't get me wrong; I'm not advocating that everyone should go out and buy a non-HD Ready TV, but if a current 480p plasma owner wants to sign up for Sky HD and has a screen that accepts 50Hz HD signals, I think the improvement in picture quality might be surprising. Try before you buy.
     
  9. Stephen Neal

    Stephen Neal
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    Yes - I accept that a local downconversion from 4:2:0 HD will benefit from the increase in chroma resolution compared to a 4:2:0 SD broadcast of a downconversion.

    I thought that you could only use the extended Kell factor vertically - but not horizontally. After all there is no horizontal interlace - only vertical?

    Presumably because they deliver only 75% of the horizontal resolution. So the 500 you claim is delivered in a 720 sample line horizontally, will be reduced to about 380 with a 544 sample line.

    However I'm not convinced with the same factor being used horizontally and vertically.

    There is also the issue that E4 is broadcast by D3/4 whilst E4+1 is broadcast by Crown Castle? Therefore they are statmuxed and coded with different channels (and E4+1 with a newer encoder I suspect)

    Difficult to know what you're comparing in that situation

    Yes - my argument was more that a 480p panel was being advocated as being capable of displaying more resolution than is present in an interlaced PAL signal. There were no caveats made about these signals being 576i 4:2:0 MPEG2. However I accept that horizontally an SD 4:4:4 signal will only have 720 samples horizontaly - whether 480i or 576i. However I suspect most downconversion from HD is based around a 720x576 SD frame - so downconversions may not exploit the full horizontal resolution either. Vertically I think that in luma terms - which are the most visible components - a 480p is close to a good match for a 576i signal, and certainly not capable of massive improvements over this.
     

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