Some observations about DVD 'resolution'....

Discussion in 'Archived Threads 2001-2004' started by Frank, Sep 2, 2001.

  1. Frank

    Frank Stunt Coordinator

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    I've been playing around with capturing DVD images from a computer and manipulating them in Adobe Photoshop.
    I have noticed that I can scale a DVD down to 360 by 240 pixels thus reducing its resolution to 25 percent of the original and the image looks just as sharp. If I then take the downsampled image and upsample it back to the original pixel resolution the images are basically identical.
    I have tried numerous tests and they all seem to point to the fact that the effective resolution of these DVDs is no more then 360 by 240 and often less then that.
    High resolution images that I downsample to 640 by 480 looks much, much sharper then any DVD. I even tried downsampling high resolution sources to 320 by 240 and they still look better then DVD quality.
    I believe that the image quality of DVDs is seriously compromised by the resolution filtering that is necessary to make them look acceptable on interlaced NTSC displays.
    I really wonder what a DVD could look like if it was mastered for a 480P display with no regard to how it looks on an NTSC interlaced display.
    Frank
     
  2. Joshua Clinard

    Joshua Clinard Screenwriter

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    I don't know, I have seen some pretty sharp image captures. I really depends on the source. I still think it is interesting though. There is a debate on whether applying NTSC produces a resolution loss or not.
     
  3. Frank

    Frank Stunt Coordinator

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    Any suggestios for really sharp movie images?
    I have tried several and none seem to have any 'real' resolution beyong about 360 by 240.
    Where is this debate by the way? I've never seen it.
    Frank
     
  4. gregstaten

    gregstaten Supporting Actor

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    Oh there is definitely the potential for loss. Most transfers roll off the vertical high frequency information as it can cause flickering when displayed in an interlaced format.
    That said, I seriously question your 360 x 240 statement. I've seen transfers that have a far greater detail than you're claiming. I'd question how you're grabbing the images.
    -greg
     
  5. Frank

    Frank Stunt Coordinator

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    quote: That said, I seriously question your 360 x 240 statement. I've seen transfers that have a far greater detail than you're claiming. I'd question how you're grabbing the images. [/quote] Fair enough.
    Care to give me some examples so I can compare them?
    I am currently using PowerDVD version 3 to grab the images.
    I have weave selected instead of BOB and I am careful to make sure both fields are from the same frame. Any other suggestions are welcome.
    Id did occur to me that the color resolution is in fact limited to 360:240. Perhaps that is the main culprit.
    Frank
    [Edited last by Frank on September 02, 2001 at 05:29 PM]
     
  6. Marc Alexander

    Marc Alexander Stunt Coordinator

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    Frank,
    I think you may be detecting a limitation of your PC DVD player. Most PC DVD solutions limit the resolution of captured stills (if it lets you capture at all) on certain flagged DVDs (I don't know how this type of flag is set, macrovision?). It could also be a limitation of the DVD still display.
    See DVD Benchmark - Part 5 - Progressive Scan DVD to learn how video is stored on Disc. My Panasonic manual states that only "I" frames while in still mode are full resolution.
    You may want to do some more research regarding how your PC DVD handles stills before drawing a conclusion.
     
  7. Neil Joseph

    Neil Joseph Lead Actor

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  8. Frank

    Frank Stunt Coordinator

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    It's a very simple matter to determine if the DVD player capture function is providing full resolution. All you have to do is play a resolution test pattern such as the ones on Avia and check the resolution of the captured image.
    It seems to be full resolution.
    Frank
     

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