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progressive scan look worse on pw6?

Discussion in 'Plasma TVs' started by SNICK, Apr 12, 2004.

  1. SNICK

    SNICK
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    I've recently bought a DVD player with progressive scan output - and to be honest I reckon it looks worse than non - prog scan!

    I have a panny pw6 - not sure whether there is anything i need to do in pic set up? or whether it detects automatically. My dvd player is a new panny dvd recorder for what it's worth.

    any suggestions? :confused:
     
  2. MAW

    MAW
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    And the player is? The trouble is, you can get the very mistaken image that a prog scan DVD is the be all and end all. You need to get the signal path and process clear in your mind. Video is stored as interlaced on the DVD, but displayed progressively on the plasma. Therefore, somewhere along the line it is 'deinterlaced'. If you have a £300+ dvd player, it's likely to do a fair job of this, H-K 27 or something like it. If you have a Hinari or other make nobody's ever heard of, which has progressive output, then built into your plasma is a deinterlacer.(it couldn't display interlaced video without it) You have to ask yourself, where is this process being done best, in my £100 DVD, or in my £3k plasma display.

    Edit: correction on process. The video is stored progressive, extracted interlaced, wouldn't it be nice to skip this step? Do HDMI players skip this bit?
     
  3. SNICK

    SNICK
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    It's the new Panasonic DMR E55 recorder - and I have set it to Prog scan output in the set up menu.
     
  4. cybersoga

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    The display will probably have a different memory when being fed progressive scan and so will need to be adjusted again. I would suggest getting a calibration disc or getting somone round to do it. Also, the dvd player's deinterlacer might need to be set to "film mode" to get the best picture when watching films (by weaving the fields together to make frames). If it has different dinterlacing settings give them a go. If the DVD player can't do film mode deinterlacing (also known as 2:2 pull down) the picture is being compromised. Oh and I forgot to mention, make sure you are using a decent component video cable.
     
  5. Mr.D

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    You were right the first time.
     
  6. MAW

    MAW
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    Mr D, I did not correct myself, but was advised of an error by one widely acknowlged as an authority on these matters. I thank you for your opinion, but for now it remains that until I check the facts for myself. Unless you could be so good as to furnish us with a link? ie proof?

    Ok then Mr. D, we have to share the humble pie as we are both 1/2 right.

    From philips licensing dept.
    It seems that as usual, it's far more complicated than we at first thought.
     
  7. cybersoga

    cybersoga
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    The true answer is "it is and it isn't" If you extract the data digitally on a computer the fields still needs to be woven together to produce film frames, on the one hand you could say that it wasn't interlaced in the first place but on the other hand it is...

    "DVDs are based on MPEG-2 encoding, which allows for either progressive or interlaced sequences. However, very few discs use progressive sequences, because the players are specifically designed for interlaced output. Interestingly, while the sequences (i.e., the films and videos) are seldom stored progressive, there's nothing wrong with using individual progressive frames in an interlaced sequence. This may sound like a semantic distinction, but it’s not. If the sequence is progressive, then all sorts of rules kick into place which ensure that the material stays progressive from start to finish. Whereas if the sequence is interlaced, then there are fewer rules and no requirement to use progressive frames. The encoder can mix and match interlaced fields and progressive frames as long as each second of MPEG-2 data contains 60 fields, no more, no less (or 50 fields per second for PAL discs). The progressive frames, when they are used, are purely for compression efficiency, but the video is still interlaced as far as the MPEG decoder is concerned.

    The input to a DVD encoder (the instrumentation that is used to author a DVD) is almost always an interlaced digital master tape, even if the original material was shot on film. The video transfer is typically done at a different facility, and the output of the transfer is interlaced. Since the DVD encoding software doesn't even have access to a progressive master, it must rely on the same kinds of algorithms that a deinterlacer uses to put the proper fields together. Since there is essentially no requirement that it actually always put the proper fields together, other than compression efficiency, many encoders are conservative about using progressive frames. If the encoder cannot be sure that a frame is progressive, it will typically mark it interlaced, because the only real loss is a few bits of disc space."

    http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html
     
  8. cybersoga

    cybersoga
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    I think the question that has to be asked is (similar to MAW's original thought) are there any dvd players other than computers able to digitally extract the film frames within the mpeg data without first converting to anologue before the deinterlacer (hence making the deinterlacer redundant)? Will HDMI make this possible?
     
  9. Mr.D

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    I'm not sure there is a need to go analogue after the mpeg2 decode and prior to the deinterlace stage in a a progressive capable player . I thought that whilst after the decode the sequence was interlaced it was still data before being passed to the deinterlace chip. I could be wrong though but it doesn't appear to make much sense to have an additional digital to analogue stage from a quality or even a cost standpoint (you'd need more components).

    Also I think it would be useful to not confuse progressive as in a coherent frame based sequence (film originated) and a frame based sequence that is in fact made up of temporally discrete fields (interlaced video originated) woven together to allow mpeg2 compression algorithms to better identify and encode non-static areas of image ( think of it as mpeg2 only having to update the moving parts of the image rather than the static areas the fact its updating hairy incorrectly deinterlaced areas makes little difference when it gets spat out as interlaced again). Both are now "frames" but only one is "progressive" and has merit in being kept that way .

    I'm also not sure if there is any real advantage in encoding a dvd as a progressive sequence anyway compared with an interlaced one. For one thing you can normally recreate the correct frame structure quite well ( apart from the 3:2 pulldown frames which should be flagged as such ...whole other story ...it should be just a question of getting the field dominance sorted and its either odd or even so if one doesn't work the other will... unless you have a totally messed piece of video).

    If you had 24p or 25p encoded discs that you could generate a useful progressive signal from I don't thinkit would necessrily look any better than properly deinterlaced discs from a decent current player.

    Also if you had a disc that was originated from interlaced material you would still need the current pipeline of mpeg2 decode folllowed by deinterlace to create a decent progressive output from it.

    So you've now got a player thats effectively got two output pipelines on it depending on disc type for what I suspect is minimal if any advantage in copig with "proper" 24p/25p discs.

    Also the seperate decode follwed by deinterlace pipeline is more robust at dealing with mastering problems on discs whereas with straight 24p path you'll see every glitch thats on there.
    ( course you could argue that the very fact the material is turned into interlace makes glitches and field dominance changes mre likely in the first place!)
     
  10. cybersoga

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    It doesn't make a lot of sense to me either but DVD players do have seperate mpeg decoders and deinterlacers, I thought I read somewhere that they have to convert to anologue and back to digital. Perhaps John Dawson would know for sure?

    I thought exactly the same thing, but then I thought, why not, were only really interested in progressive scan where the fields are meant to be woven together, but I also thought what would happen if 1 field was missing half way through a film (bad edit) then it would start weaving the wrong fields together and you'd have constant combing for the rest of the film, at least a deinterlacer would detect and fix that!
     
  11. symanski

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    The conversion to analogue is very much the final stage! Until then, it's treated as a computer would - as a series of ones and zeros. All the processing is done in the digital domain, only the results are then converted to the real analogue world.

    All the best,

    Dr John Sim.
     
  12. cybersoga

    cybersoga
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    http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=157417

    "Put simply, the data stored on a DVD is never converted to analog until the output. All current doubling, quadrupling, and scaling technologies convert the video picture information to NTSC (Never Twice Same Color,) then convert that signal to digital and then de-interlace and scale. The Movi M2000 never converts anything to NTSC. The video picture information is digitally extracted from the DVD and scaled to the selected Hi Definition TV resolution."

    This isn't the only place i've read it, i'll try and find where it was. The fact he says that dvd players convert to NTSC is wrong for a start, most half decent dvd players output component.
     
  13. symanski

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    NTSC problem with the colour is mainly caused when it's transmitted. If you're using it in baseband and it's connected with say component or RGB output, then you won't have the usual Never Twice the Same Colo(u)r problem.

    Getting back to the original thread, sometimes I too find that a more direct feed of RGB (in to the VGA input) can give a better and sharper picture than progressive video. I've changed my system round again to experiment, so have Sky in via the RGB to Plasma VGA unit, and progressive component for the DVD.

    All the best,

    Dr John Sim.
     

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