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DVD Playback on a PC (or Xbox) Large solid blocks of colour esp in dark scenes. WHY ?

Discussion in 'Desktop & Laptop Computers Forum' started by Tempest, Nov 7, 2003.

  1. Tempest

    Tempest
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    Perhaps someone here can explain the following.

    When I view a DVD on my PC, some DVD's especially in dark scenes, if you look carefully, you can see large blocks of solid colour moving about.

    Not sure if it's what you call mpeg artifacts or what,
    Like in a scene where someone is in a cave. If you look into the blackness, the black is made up of large areas of browns, dark greys etc. they move about with the movie.

    Now I have always notice this on PC playback of a DVD.
    I have upgraded my CPU and tried 3 different software players, I even changed graphics cards (from a matrox to a voodoo) and I still see these.

    Even when playing DVD's on the TV Via an Xbox I can see this kind of thing happening (well it's a PC isn't it)

    The thing is. I don't recall every seeing my real DVD player showing these blocks of colour. Almost as if it has special ciruitry to smooth these patches of colour out......

    I'm not alone in this as I brought this Xbox and bocks of colour in dark scenes and others also said they had sometimes notice this too.

    But, we are all saying how a HTPC gives the best image quality.

    So now I'm confused...............

    Can anyone explain what I'm seeing and what they do about it ?
    Is it down to graphics cards, and changing to a Radeon will stop the issue?

    I'm just puzzled right now as in the past (until I read about HTPC) I would have said a real DVD player was better.
     
  2. Home PC Nut

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    Simple possible solution. Try and adjust the contrast/brightness/tint/colour settings on your TV/PC Monitor/PC DVD Player.

    What you are probably seeing is like you said the MPEG2 compression. Most TV's come with factory settings which are not accurate as the brightness/contrast is usually set way to high. Get yourself a calibration DVD or use one of the THX ones on a THX mastered DVD from the last 3 years or so. Some DVD's also contain their own Colour Balance screen although I cannot think of one at the moment even though I own a few with them. Try www.thx.com as they used to have a downloadable THX optimiser on there. Not sure if they still have it so perhaps do a web search as well.

    Another possibility is that your DVD player uses another cable to connect (say RGB) and can auto detect the correct colour balance for the TV whereas an Xbox may use a different cable and may not contain a circuit to detect colourspace as it is after all a cut down PC with 2/3year old technology inside and not really a very good DVD player as it uses budget DVD components to keep the cost down.

    You can also adjust the PC DVD Players picture settings to compensate. Some GFX card's also have software to adjust gamma settings check that as well.

    A HTPC is definately superior to almost every standalone DVD player and does give the best quality when setup correctly but is more complex as you have control over every setting so more to consider than a standalone DVD player.
     
  3. Kramer

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    Run hardware acceleration & check your gamma settings.

    Should sort it :smashin:
     
  4. rob_w

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    I'd agree with the gamma settings being out - my hcpc needed them changing to lose the 'blockiness'. It's fine now.


    Rob
     
  5. Gary Lightfoot

    Gary Lightfoot
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    Setting the white and black levels via Avia (needle pulse tests) will usualy do the trick, as well as doing the above. :)

    Gary.
     
  6. Jeff

    Jeff
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    Could be;

    Original source
    Mpeg decodeing
    Graphics card (hardware)
    Graphics card video settings
    Display

    and while the XBox approximates a PC in hardware terms, it certainly isn't a HTPC. A HTPC has hardware and software dedicated for HT use. This would normally mean a Radeon and one of the better software DVD players like Theatertek or WinDVD.
     
  7. Tempest

    Tempest
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    Cheers for the advice.

    Must admit was not keen on the suggestions about gamma/brightness settings type of suggestions.

    This to me just implied hiding the problem.

    I'd happier accept it was a hardware / software issue.
    Or also the DVD quality issue.

    I just tried power DVD5 and on a very dark film (Dark City) I must say it looks pretty good now.

    So with a Radeon added it would be the icing on the cake.
     
  8. Gary Lightfoot

    Gary Lightfoot
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    Never heard calibration refered to as 'hiding the problem' before. ;)

    Gary.
     
  9. Jeff

    Jeff
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    There is nothing to calibrate on a Radeon card. The overlay settings are digital, anything other than defaults (ATI) and you are altering the picture from the correct RGB values to something else.
     
  10. Gary Lightfoot

    Gary Lightfoot
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    I meant the display. AFAIK, you set the Radeon to certain values (like those reccomended for TT), then set white/black level at the display via Avia for example.

    Gary.
     
  11. Tempest

    Tempest
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    Well, sorry :)

    But sounds like it to me.....

    Problem = I can see Mpeg blocks of colour caused by the compression format.

    Answer = turn the brightness down so you can't see them


    Hmmmmmmmmmmmmm, sounds like hiding to me :)
     
  12. Gary Lightfoot

    Gary Lightfoot
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    Well, you obviously know best. ;)

    You carry on looking at your blocky display, and we'll carry on looking at our smooth artefact free images. :D

    Gary.
     

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