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Pixelated affect on LCDs

Discussion in 'LCD & LED LCD TVs Forum' started by benwong, May 12, 2005.

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  1. benwong

    benwong
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    Hi guys,

    Just an observation really. I've been looking to buy a top notch LCD screen in the near future, and whilst wandering around the local shopping centre with the girlfriend (Watford Harlequin) I stumbled across both a Sony shop and a Panasonic shop. Although my short list does not comprise of anything from either of these manufacturers, for purely research purposes (and to get away from the dreaded "I'm-only-gonna-be-5-minutes"-which-ends-up-2-hours clothes shopping), and I walked into these shops to have a look at what they had to offer. ;)

    Standing within 5 feet of these 32" screens, I couldn't help but notice what I can only describe as a pixelated affect. Both shops were receiving their feeds from Freeview boxes, and good old Trisha was on in both shops :eek: When the camera wasn't zoomed in on her face (ie Trisha was in the distance), her face was not defined at all well. It looked like there were flies buzzing around in close proximity her head as well as landing on her face. I then looked at the similarly spec'ed plasmas that were there and none of them exhibited this phenomena. Even the larger plasmas did not suffer from this at the same viewing distance. :rolleyes:

    Now I know that these 32" screens are not supposed to be viewed so closely, but the fact that a 37" plasma did not have this affect at the same distance has kind of put doubts in my head.

    I realize that Plasmas have problems of their own (fewer are HD ready etc.), and my intentions are not to start a now already overly covered LCD vs. Plasma debate :nono: However, my point is: are all LCDs like this?

    I've not had the opportunity to view any of my short list in a proper setup just yet, but I have a very good idea (thanks to my local currys) as to how each screen fairs with very poor feeds! :smashin:

    Incidentally, I feel I'm the reverse of most people on here: I'm not actually worried about how each screen deals with poor feeds, I'm more interested in how they look with good sources!

    Now is this just a case of 'lcd's are of higher quality' and so they show up the inadequacies of our Freeview service?

    It was a major anticlimax when I saw these screens, and has had me a little uneasy due to the fact that I'd like to watch Freeview (as well as DVDs etc.)on the new screen when I eventually purchase one. :rolleyes:

    Any ideas?

    Ben
     
  2. matt_p

    matt_p
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    Think the safest word to use here is 'resolution' rather than 'quality'! The digital artifacts you describe are visible on all types of screen, it's just easier to see them on a LCD due to the higher resolution.


    Er... make your mind up!! :D

    I think the answer is: Don't watch a 32" LCD from 5ft away! Once you are a reasonable distance away (9ft at least I'd say), you should get good results even with freeview.

    matt
     
  3. benwong

    benwong
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    Matt,

    Surely if you're getting a normal pal picture via Freeview, any TV screen will be displaying this picture at the same resolution as it was transmitted at. I understand that the picture is being shown on a 1366x768 resolution screen, but that doesn't explain why the extra brown pixels around the head (but not on the head), if this didn't exist in the original broadcast. If they did exist in the original broadcast, it would show up on the plasmas and CRTs as well because they are all displaying the picture at the same amount of detail as it was transmitted at. In fact the Plasmas have a higher resolution than the original broadcast, so surely I would have seen this affect on them as well, especially when I was looking at a 37" AND 42" screen all within 5 feet. I did not see such artifacts on these screens.

    Please let me know if I'm very wrong in my above assumptions.

    Ben
     
  4. matt_p

    matt_p
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    The artifacts you describe are part and parcel of Freeview, Sky, NTL or any other digital transmission. You get it on the poorer channels and I've seen it many many many times on my old CRT, my dad's plasma and my LCD. It is certainly not a problem specific to LCD, but I have found that it's more noticable on my LCD because my LCD has a clearer picture than the CRT or plasma I have judged it against. I don't know the technical ins and outs of resolutions etc, so I can only speak as a layman.

    Why you only saw it on LCD and not the others, I don't know. Perhaps the shop feed was not equal in quality to all sources, different sharpness settings, maybe some sets had noise reduction etc... Can't say for sure. All I can say is that if the set has a reasonably decent feed and you are a proper distance back from the set, it won't be a distraction.

    I'm watching my hitachi 32ld7200 now and it has a great picture. If I set the picture back to manufacturer's default and sit 3ft from it, then yeah, the picture is rubbish. But who in their right mind would want to do that? :D
     
  5. mickbarlow

    mickbarlow
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    LCD are designed for HD feeds so pumping a SD feed through is obviously not gonna work too well, whereas CRT's are designed for SD feeds.
     
  6. VanBurenPhilips

    VanBurenPhilips
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    In response to the original poster, I'd have my doubts about buying an LCD or Plasma if high-definition sources are not your priority. I bought mine for DVDs and (480p or higher) videogames - I watch a lot of films and play a lot of games, and the improvement over my old CRT is immense - but normal TV viewing just wasn't a priority for me. ntl via RGB Scart varies a great deal, a good channel/programme will look significantly better than CRT, a poor one will more-than-likely look worse (to most people - there's no definitive way to argue this, everyone's preferences are different). But if this was my main concern, I wouldn't have bought one.

    If you're planning on watching HDTV from Sky or ntl next year, then it's maybe worth considering, but I'd be hard-pressed to find an argument against waiting til the HDTV services (and more TVs) are actually available. If TV viewing is top of your list of priorities, I think you're probably better off holding onto your cash for now. You could buy a new CRT... no doubt for the price you'd pay for a decent LCD or Plasma, you'd be able to get a CRT that's very flattering to SD TV signals... but IMO that'd be a bit short-sighted (you may regret it when HD material becomes more common).

    Another alternative would be a DLP rear-projection set. I hear these have the closest to a CRT-like display while still offering HD functionality. I haven't seen one in action though and I don't really know much about them, so don't take my word.

    I'd say you should identify the sources you're likely to use primarily (ie, Freeview and I guess your DVD player) and, where possible, arrange to take them to the store and see them in action - same sources on different sets so you get a proper comparison. This stuff is really subjective, I could recommend my new TV, which I'm really happy with, and to you (with the sources you'll be using) it might look awful. You've really got to see for yourself.
     
  7. Rob1698

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    The artifacts you see are caused by the MPEG encoding used for digital transmission, not by the LCD itself.
    The fact that you see them on LCD is caused by the fact that LCD has a much higher resolution than standard TV, and to make the best picture on that resolution the digital processing in the TV "enhances" the picture to extract extra pixels out of the original content.
    This works OK when the original content is analogue (PAL) or good quality digital, but when corners have been cut while compressing the digital signal you wll see the artifacts amplified when the pixel-upscaling processing is applied to it.

    To overcome this you need a good quality signal, such as satellite or good quality analogue PAL. "digital terrestrial" or "digital cable" is often compressed too much, to fit more channels in the limited bandwidth of those media.
     
  8. Pedant

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    I see this all the time on sky and a crt. annoys the hell out of me as I keep getting after images of compression. I don't see it all the time, just, I guess, when the algorithm calculates you won't see it. Obviously way too agressive.
     
  9. SeanT

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    A VERY cheap scaler has almost obliterated this over NTL, it's just part and parcel of the poor signal and budget upscaling - it is still noticeable, but only within a couple of feet!
     
  10. benwong

    benwong
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    I know of and understand MPEG compression artifacts, and I have witnessed them countless times on my existing CRT whilst watching Freeview. The fact is, this affect I was seeing didn't come across as something derived from this compression, well if it was, it wasn't something i've ever noticed on my Freeview box. :confused:

    I know that Freeview channels do get overly compressed, but I was under the impression that the main channels (IE BBC1 and ITV1) had more bandwidth than the other smaller channels, and so these ones would be on par with the higher quality ones from Sky (having said that, the majority of Sky channels are over compressed anyway). :rolleyes:

    ALL the screens on display were showing a freeview feed of ITV1. Some were originally showing Sky News which was absolutely awful, and I physically changed the channel to check the quality of the main stream channels.

    This bit does make sense to me, and I suppose it would probably explain it.. if only I had screen shots so I could point it out for you!! :rolleyes:

    @Piln,

    I was looking for a screen that would be great with DVD sources, as well as Freeview. I have read up extensively on future proofing (HD sources etc) and it is for this reason that I'm considering LCD screens. I also require a screen which doesn't take up as much space as my 24" CRT Philips currently occupies.

    The only other logical alternative would be Plasmas, but the majority of them are not HD ready, and they are simply too big for my room.

    Ben
     

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