Toshiba 42wh36p progressive flicker

Discussion in 'General TV Discussions Forum' started by cjking, Apr 22, 2004.

  1. cjking

    cjking
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    In a shop recently I changed the setting of a 42wh36p from "natural" to "progress" and found that the background (large area of solid colour) flickered. I have read in these forums of this happening with other Toshibas that have these modes.

    Can anyone put my mind at rest and tell me this won't happen with a progressive scan signal from an external source? (I have no rationale for this hope other than wishful thinking...)
     
  2. cjking

    cjking
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    If normal 50Hz TV is 50 fields (half-frames) per second, and Natural/Active/100 Hz modes (which are all described as 100Hz on Toshiba web site) are equivalent to each other, shouldn't a PAL progressive signal which displays 50 full frames per sec. be equally flicker-free? Or maybe despite the fact that the same number of lines per second are being painted as for 100hz, the bigger time gap between anything being painted in one area of the screen means flicker? If this is true then the progressive inputs on the Tosh are a complete waste of space from the point of view of getting a top quality deinterlaced signal to the Tosh?
     
  3. cjking

    cjking
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    The following quote is from the manual, apparently, though I've copied it from another thread. Is the manual saying that progress mode has more background flicker?


     
  4. cjking

    cjking
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  5. Lizzard

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    Yes progessive flickers more than 100Hz, that's correct, but the overall picture is much better when watching on the Toshiba RPTVs.

    You get rid of the scan lines once and for all with the "progressive" mode.
     
  6. Demon

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    I am very rusty on the whole Prog Scan technicalities, but from what I remember, and please, any experts jump in and correct as necessary..

    The problem with Progressive scan, is for PAL material at least it is only 25fps... and thats where the problem lies....
    The original film is recorded at 25fps, but to 'reduce' flicker, each frame is shown twice..

    To claim true progressive scan, the Toshiba is simply displaying the pitcure as it is supposed to be, so a 25Hz PAL progressive is 'double shuttered' upto 50Hz.. and as we all know 50Hz has a noticeable flicker, this is more evident on a 100Hz TV, since its phosphors are chosen to decay faster then a std 50Hz set to ensure the full benefits of 100Hz are seen.

    In the US, the source films are recorded at 24fps, but use a 3:2 pulldown method to actually display it at 60fps.. which obviouly has much less apparent flicker..

    now the issue that manufacturers face when deciding to make their 100Hz TV Prog scan is do they display the prog-scan in its natural form i.e. double framed 50Hz for PAL and 60Hz for NTSC, or do they process the prog scan, which may loose some detail and try to get less flicker???

    As already mentioned, the 100Hz sets have much faster phosphors, since they are processing the picture twice as fast as normal, if they used the same slower phosphors as 50Hz sets then they effectively loose some bandwidth for the 100Hz processed picture, and this will mean loss of detail or similar...

    I have only seen a few PAL prog scan TV's and they have all flickered in PAL Prog, and been much more stable in NTSC prog scan... so I am not sure it Toshiba are alone, and if someone else makes PAL prog stable, is it at the expense of detail???

    I don't know the answer.. I have tried some PAL Prog DVD players on my 51WH36, and all the cheap ones look much worse then my SD330 on interlaced component... my Brother has the SONY 930 DVD player, and we can't see any real difference in detail between the Prog scan and interlaced.. there are no less jaggies etc...
     
  7. cjking

    cjking
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    There's something I don't understand about CRT projectors - do they have phosphors?

    I can see that having faster decaying phosphors on a 100hz CRT TV might cause a problem when you switch to a 50hz progressive signal.

    I assumed (in my ignorance) that a CRT projector didn't have phosphors and that it just projected three beams of coloured light. If there are no phosphors to decay gradually then they should be much more prone to flicker than a CRT TV. Presumably they would only be relying on persistence of vision in the eye.

    While we're on the subject, does anyone know anything about 100hz picture processing - how does it work, is there deinterlacing going on.

    It seems I've been fixated on progressive scan for the last few years, regard CRT in all its forms as ancient technology, meanwhile the makers have been developing different forms of picture processing that may do just as good a job but are only appropriate to CRT devices. (For most of the last five years I've been assuming my next TV would be based on digital panel.)
     
  8. Lizzard

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    Demon

    I don't have a component-output progressive DVD player so i haven't tried the component inputs but all i can say is that i run a highend RGB SCART to my 57" and i have tried all different picture modes and the "progressive" mode is much better than "natural" and all other modes.

    In all other modes i can detect the scanlines, but with progressive mode the picture quality is just stunning, no scanlines at all.

    However it flickers more than the other modes but i have become used to it now and doesn't take notice of it anymore.

    I don't know why you can't see any difference on your 51" between the modes, maybe because your screen is smaller than mine or that your mechanical focus isn't as sharp as mine.

    As the action is in the middle of the screen i have focused the CRT-guns to the center as sharp as i can, however the sides are very sharp also, but i have chosen to always have the sharpest picture where the action is when watching.

    Some american ISF-engineer told me this is the best to set it up, some people say you should have even focus all over the screen, as your eyes is often in the center of the screen where the action happens.
     
  9. Lizzard

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    100Hz is just higher scanrate, nothing else.

    Progressive writes all even and odd lines in one sweep, that's why the scanlines get removed, it's still 50Hz.
     
  10. cjking

    cjking
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    I should have been clearer with my question with my question about 100Hz processing. I was thinking of the things like the Toshibas Natural and Active modes (which are also 100Hz modes.) It is clear from the documentation about Activevision on their web site that they are doing complicated things like detecting motion of objects in the picture in order to "caculate" improved pictures. This is similar to what my Iscan does when it is deinterlacing to produce progressive scan frames. I guess what the difference may be, is that the Toshiba (to avoid large area flicker) is doing it with the object of doubling the signal by doubling the number of fields rather than doubling each field to get a progressive frame. The simplest way to do this would be for it to generate a single progressive frame in a similar way to the ISCAN, then instead of displaying it twice as it does with progressive mode, chop it into even and odd fields and display each pair of fields twice to give a 100Hz picture. Because the deinterlacing was already done the fields won't be in conflict with each other so there will be no interlacing artifacts. (The chopping is only necessary because presumably the hardware can't cope with showing the full frame 3 or 4 times to reduce flicker, whereas we know it can show 4 half-frames because it is a 100hz set.)

    The above approach would be optimum for movies, and I would have thought that for movies this algorithm in which the time between interlaced odd and even fields being painted is halved would look like progressive without the flicker. If the set could do this then it would be no trouble to offer the option of displaying a progressive signal from an external source using this option. Unfortunately it looks like this option is not there.

    For video sources (e.g. sport) it might be even cleverer (and give a better final result) to say: we are not actually starting with 2 fields that are supposed to combine to form a frame, what we have is 2 frames at half resolution that show the real event at slightly different times, so don't try to combine them, but generate intermediate fields using interpolation to double the field-rate. Because the field rate is doubled, edge flicker that you get with interlaced video would be at 50Hz instead of 25Hz, so probably not noticeable. (I'm not sure whether this suggestion would get rid of or reduce other interlacing artifacts.)

    So my question really was: does anyone know if Natural/Active modes are doing anything like what I'm describing?
     
  11. nero0410

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    cjking---hey just looked through the forums for your latest post i was wondering if you got your tosh 51wh36 through from arogs yet as i have not got a choice but to order from argos as i have a few hundred pounds worth of vouchers for there and i am ordering one this wed or thurs (28th or 29th april) hope you've had some luck
     
  12. Smurfin

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    You're not actually seeing "true" progressive scan then: it only works (I believe via the component connection).
     
  13. Lizzard

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    Actually not, progressive handling can be inside the TV or from a external source.

    However you can't input progressive signals on anything except component inputs.

    But that doesn't matter as the Toshiba got internal progressive handling on all inputs and therefore it's not necessary really to have a progressive capable DVD player as the Toshiba does the job as good.
     
  14. Smurfin

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    So if the DVD player is outputting interlaced the TV converts it to progressive:confused:
     
  15. Lizzard

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    Correct, and only if the TV got that feature builtin like the Toshibas.
     
  16. cjking

    cjking
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    My set arrived Saturday. I'm still to busy playing with it to post a full report, but I thought I'd post a quick note in this thread.

    It turns out I was worrying for nothing.

    My set was delivered at midday, and I had two rugby semi-finals to watch before I could start setting it up properly. During the rugby my (analog cable) pictures were pretty horrible, extremely grainy, and the set flickered horribly in progressive mode - progressive mode was completely unusable.

    In the evening I turn contrast down from 100 to 25 (which seems to be optimum for me) and did the user-level convergence. I also tried turning brightness down from 50 to 35 and colour from 50 to 40. The graininess disappeared and so did the flicker in progressive mode.

    I'll say that again: the 50hz flicker disappeared completely - it is now a complete non-issue.

    I'm watching from very close up, the surface of my eyeballs is seven feet from the surface of my 51" screen. In Natural, Active and 100 Hz modes I can just make out scan lines, with progressive they disappear. I now intend to always use progressive mode.
     
  17. cjking

    cjking
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    Based on a day and a halfs experience, I would agree with Lizzards comment that you do not need a progressive scan DVD player with this set.

    It really depends on how much money you have and how important it is to get the best possible result. The internal progressive scan gives you 95% of the improvement you can expect, just by getting rid of scan lines.

    I did notice once scene in one DVD I looked at where my external de-interlacer did a better job of getting rid of interlace artifacts on the edge of a table than the internal one, so it is possible to get some improvement though.

    The point is, don't just buy any DVD player that puts out progressive - you have to know what chip it has and whether it is any better than what is built into the Toshiba. Even if you buy the best, there is only very small scope for it to improve on what the Toshiba is already doing.
     
  18. DTS0077

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    " I would agree with Lizzards comment that you do not need a progressive scan DVD player with this set. "

    Hmmm...thats very interesting......no one mentioned that last year when loads of us were purchasing these!

    I must admit when I went from the Tosh 220e player to the 530e I wasnt that impressed - I was expecting alot more.

    However I must say my new player Cambridge Audio 540D is a much much better machine. The picture difference is quite clear, the 540D progressive is quite awesome! :thumbsup:

    How can I further test this player? Reading Lizzards & CJkings posts - they mention certain DVDs for testing. Anyone know what these? What should I be looking for? Chapters?

    I just wanna be certain that the 540D is the one!
     
  19. cjking

    cjking
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    I've had my set for much longer now, so I can update my comments.

    The sets Progress mode gets rid of scan lines and in that sense gives you most of the improvement that you would want from progressive scan on a CRT/CRT projector display.

    If you look out for them, and sometimes even if you don't, you will still see de-interlacing artifacts.

    On the beginning of "Crouching Tiger" in the opening seen, as the camera goes through the house where Lee Mu Bai is meeting Michelle Yeoh's character (not sure about spelling) you see artifacts on the edges of furniture. When he moves to sit down with her revealing a round table behind him you will see them on the edge of the table.

    I watched the same scene with a Toshiba SD510E and it got rid of these artifacts, so it's better than the built in Progress mode. On another movie, "Intolerable Cruelty" also near the start, when the guy comes up to his house and finds a lable on his front door, the box around the lettering when he reads the lable flickered with the SD510E, but didn't flicker with my Iscan Pro, so a Denon 2200 (which has the same chip as the Iscan) will correct errors the SD510E won't. Earlier in that movie when the guy is driving to his house, the tiled roof of a house in the background showed an artifact with all three de-interlacers (TV, SD510E and IScan.)

    Another example, in one of the opening scenes of "Liberty Heights" the mother is wearing a black and white striped shirt - Progress mode goes beserk with artifacts but the Iscan solves them.

    Against all this, set the fact that I watched a couple of movies (I think "The Quiet American" was one) without noticing a single artifact - it helps if you don't look out for them.

    So there is extra improvement to be gained from getting a progressive scan player, but not all players are equal, and even the best player will sometimes get it wrong.

    On the subject of 50Hz flicker, give that progress mode is a 50Hz mode, I find this tends not to be a problem with drama (whether DVDs or TV) but for other types of programming, especially where there are studio backgrounds, it can be a bit of an issue. In an ideal world I would watch ordinary TV from a distance of 12 feet or more (to my 51" screen) using the 100Hz modes, as at that distance scan lines are less visible and apparent picture quality is higher, and DVDs from seven or eight feet using progress mode.

    DVDs have a high enough picture quality to stand being watched from close-up, but my analog cable TV pictures, which look very good from a greater distance, show their flaws when you sit up close. For the same reason, my replacement Super-VHS VCR, which is only a year and a half old, is now a white elephant. On a screen this big, even a Super-VHS recording made (for testing purposes) from a DVD source via S-video connection was so imperfect that I've concluded I will never want to use Videotape for recording in future. I don't actually record anything these days anyway, but if I do feel the need to offload something from Sky+ (when I get it) I will have to try a DVD recorder.
     

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