What is HD ??? (and what's close to it?)

Discussion in 'General TV Discussions Forum' started by JohnCCFC, Feb 24, 2005.

  1. JohnCCFC

    JohnCCFC
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    I understand the basics (HD is clever tv combined with clever sources = better picture) and I have seen a demo (which is mind-blowing/mouth-watering) but I am so confused with standards and formats and resolution.

    The reason for my question is, not how can I get it, but on my current setup how near can I get to it. I have a Samsung plasma (852 x 480 ish - forgive my inaccuracies) which I know is SD (not that I fully understand SD either)

    I have a component, a vga, a DVI and two scart inputs. My component input states '480i, p/576i, p/720p/1080i'.

    If anyone has the patience I coud really use a short explanation of what's what. I've read mountains of stuff but am still confused. I'm trying to improve my PQ without an actual HD setup (my panel is new and I had no choice than to get it - long story). In relation to the 'i' and 'p' formats, which add-on boxes improve PQ to which level.

    If it's a dumb question caused by my mis-understanding, then I appologise in advance.
     
  2. Peter Parker

    Peter Parker
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    SD= Standard Definition IIRC.

    I don't think you will see any resolution improvements on your plasma, but there may be improevments in the image quality from a better transfer compared to DVD, so that might notice. I use a PC as my source into a projector, and that gives me a better picture than any DVD player, so maybe that would work for you too.

    You won't start to really appreciate HD stuff until you have an XGA or higher res display IMHO.

    Gary.
     
  3. AML

    AML
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    You will need a new display that has a resolution of 1920X1080 (full HD specs @ 1080i) or at least 1336X768 (near full spec HD @ 720p).

    Thats not all. The new display also needs to have fully HDCP (copy protection) digital conections. Like HDMI or DVI-D.
    The type of DVI your display has now wont be HDCP so it wont work.

    To begin with component will be viable as a conection but as new formats like HD-DVD and Blu Ray, as well as Sky HD come out, you will need these new digital conections.
     
  4. betamac

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    You can improve DVD picture quality by using a PC to upscale a image then let the plasma downscale it, this in my expeience and many others gives a cleaner picture

    You cna also play HD material using th PC and as said above even on a SD plasma picture quality is a big improvement over DVD

    I have 2 HD movies Shrek 2 and Braveheart both look very sharp,
     
  5. JohnCCFC

    JohnCCFC
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    Your answers are really helpful thank you. Forgive me a couple more questions.

    >> 1920X1080 (full HD specs @ 1080i)

    Is 1080i the name for a standard based on the number of lines?

    When my component input says '480i, p/576i, p/720p/1080i', what does this actually refer to?

    What (format/resolution) does sky+ send?

    What would an upscaler do to the format/resolution?

    I trying to get a flavour of the shades of grey between SD and HD (not that I know what format/resolution SD is.
     
  6. Nick_UK

    Nick_UK
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    Sky's current resolution is 576i - which is 576 lines interlaced. The picture is actually 625 lines, but around 50 lines are not displayed (being part of the field blanking, which is where teletext and other data signals reside).

    "You can't make a silk purse out of a sow's ear". Up-conversion will not add quality to a picture that wasn't there to start with. What up-conversion will often do is to convert the output from interlaced to progressive which often results in a cleaner vertical resolution on some (but not all) plasmas and projectors.
     
  7. NicolasB

    NicolasB
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    The number in 720p, 1080i, etc. is the vertical resolution, sometimes referred to as the "number of lines" - i.e. the number of horizontal lines of pixels. The "i" or "p" stands for "interlaced" or "progressive". An interlaced signal is one where each frame actually consists of only half a picture - so you get lines 1, 3, 5, etc. in the first "frame" and then lines 2, 4, 6, etc. in the second. By contrast, with a progressive signal each frame consists of a whole picture.

    British television (often referred to, slightly inaccurately, as "PAL") is 576i, 50Hz. So you get 50 "frames" per second, but the signal is interlaced, so there are only actually 25 pictures per second. The resolution of the picture is 720x576, regardless of whether it's a "normal" or "widescreen" signal: with a widescreen broadcast the picture is stretched horizontally, but there's no actual extra horizontal resolution. (This is what Sky+ produces).

    American or Japanese TV ("NTSC") is 480i, 60Hz. The resolution is therefore 720x480, and there are 60 "frames" per second, each containing half of a picture, so 30 pictures a second.

    High-definition usually comes in two varieties: 720p and 1080i. In america it will be a 60Hz signal, in this country probably mostly 50Hz. 720p has a resolution of 1280x720 pixels, but it's progressive: each frame is a full picture, so you're getting 50 or 60 pictures per second rather than 25 or 30. This makes it particularly suitable for watching (e.g.) sports, or something with very fast-moving objects, as the motion is smoother.

    1080i has a resolution of 1920x1080, but is interlaced, so you actually get only 25 or 30 full pictures per second again.

    With a display like a plasma what appears on the screen has to be the same resolution as the screen itself is, so a plasma uses a "scaler" which is a device that takes a picture of one resolution and converts it to a picture of a different size, preserving as much detail as it can. Plasma TV will have a built-in scaler, but sometimes a stand-alone scaler box can do a better job. There are some advantages to not having to scale an image at all, so (for example) if you have 1280x720 pixel display then it will likely do a very good job of displaying 720p. Upscaling an image (making it bigger) will, if done properly, not significantly affect the image quality. Downscaling it causes loss of information.

    You obviously can't see any more detail on a plasma than the physical resolution of the screen. So in your case high definition is unlikely to make much difference, and indeed you are actually losing some detail even on a standard definition signal because the 576 line image is being scaled down to 480 lines.

    A 1024x768 plasma will (probably) look significantly better than an 852x480 screen does playing back HD, but you wouldn't get any advantage looking at 1080i rather than 720p - in fact, 720p will look better because of the higher frame rate. Even 50" plasma screens can have resolutions only up to about 1366x768, so they still don't get the full benefit of a 1080i picture. There aren't many displays capable of displaying a 1920x1080 picture accurately, although there are a few, for example the Sharp LC45GD1E (which is an LCD display).
     
  8. JohnCCFC

    JohnCCFC
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    NicolasB,

    You are an absolute gent, thanks for your explanation.

    I wonder why 'UK ready' plasmas only come with 480 lines instead of 576. Though, I suppose they are 'US ready' (that'll be why, I'm sure)
     
  9. Peter Parker

    Peter Parker
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    The term 'ready' quite often means that it can accept those signals. Actualy displaying them at that resolution is another matter.

    Many displays will no doubt be advertised as 'Hi Def ready', even if they're only 852 x 480, it just means that an internal scaler will accept and convert 720p or 1080i down to the panel resolution.

    Many tvs were advertised as 'digital ready' which may have sold more, but really all it meant was that a set-top box could be attached, as they didn't contain a digital tuner.

    Gary.
     
  10. NicolasB

    NicolasB
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    Probably. It's probably also to do with the fact that the same glass is used a lot in commercial displays that are driven by a PC. This is presumably why larger-screen plasmas tend to have a vertical resolution of 768 lines rather than the (apparently more logical) 720.
     
  11. Dutch

    Dutch
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    Gary,

    The new HD ready logo can only be put on screens that have a vertical resolution of at least 720, so that Panasonic et al can't put them on their 480 line models.

    Steve
     
  12. woodgaz

    woodgaz
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    Fantastic summary Nicholas B. I have been asking this on the HD thread and you have answered literally ALL of my questions with that.
    I have a PW6 with 852x480 resolution and am really really happy with it. The HD monster looming round the corner has made me question my fairly recent purchase but it would seem that it is still pretty much as good as it gets if it is properly set up. No other displays seem to be FULLY HD capable at a sensible price and there isn't any significant volume of HD media as yet. By the time there is the screens will have caught up and come down in price. Futureproofing at this stage is a bit of a guessing game IMHO.
     
  13. Chris Muriel

    Chris Muriel
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    Great summary/explanation, Nicholas B.
    I get involved with this field regularly at work (IC firm I work for makes, amomgst other things, video encoders and decoder chips) but I always have to work out exactly what customers (and most of our sles engineers) are trying to achieve when they ask me about this topic.
    Sometimes they ask about 1 standard or resolution when they really mean another.
    Got caught the other day when a customer mentioned RGB565 (which I hadn't come across before). I mistakenly thought he was referring to ITU-R BT656 until I Googled RGB565 and found that x-boxes (amongst other things) use it.
    I have saved your words into a text file for future lookup.

    Chris Muriel, Manchester.
     
  14. Nic Rhodes

    Nic Rhodes
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    Good post Nic B, best explanation have seen of this in ages and does not go to 20 pages !!
     
  15. the klang

    the klang
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    quality !
    nicolasB that was one of the best explanations iv read.i also will save that one for future reference.
     
  16. Stephen Neal

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    The only clarification that I think needs to be made is that 50 or 60 Hz interlaced formats don't use their two fields to deliver 25 or 30 full-frames every second. Instead they deliver 50 or 60 half-frames (fields). This may sound like the same thing - but if an object is moving you get motion sampling at 50 or 60Hz with a 50/60i system, not 25 or 30Hz, so you get more fluid movement with a 50/60i system than you would with a 25/30p system. Effectively the two fields that make up a "frame" can be taken at two different moments in time - they aren't two halves of the same frame taken at one moment.

    This is why if you don't de-interlace properly when displaying an interlaced source on a progressive display (like a PC_ you see "tearing" or "combing" where the two fields become obvious within a frame. In the 50Hz world this is only an issue with sources that have field-rate movement (like most normal video cameras). With film sourced material, both fields are taken from the same frame, so there is no motion between them, so no requirement to de-interlace process in the same way.

    The disadvantage of interlacing is that effectively fast moving objects have lower resolution (i.e. half the frame resolution) than the same object captured using a full progressive system with a frame rate matching the field rate of the interlaced system.

    In other words 50i is not as sharp on moving objects as 25p or 50p. However 25p will look less fluid than 50i or 50p - as it is capturing motion at half the frame rate. (The classic "film" vs "video" look)
     
  17. Dean

    Dean
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    Have to agree, that explanation has ironed out a few things that even had me confused.. nice.. apparently Sony are bringing there high end Qualia range of LCD/projector's which are true HD compatible, bet they cost a bomb though.
     
  18. mjcairney

    mjcairney
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    NicholasB - unless this is the sort of work you are involved in, I would say that you have definitely missed your vocation in life - the best explanation I have ever come across bar none.

    I too have saved it as a text file in order that I can refer back to it as and when - EXCELLENT!!

    :thumbsup:

    Cheers,

    Martin.
     
  19. Stephen Neal

    Stephen Neal
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    Having seen the Qualia rear projection set whilst on holiday in New York earlier this year I can confirm that they are truly excellent. I only saw 24p material on the model I saw, and it was in a darkened room, but the quality was so much higher than every other TV on display it was really impressive.
     

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