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Macroblocking?

Discussion in 'Beginners, General Questions' started by Al.Anderson, Nov 9, 2005.

  1. Al.Anderson

    Al.Anderson Cinematographer

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    A review I just read (Charlie and the Chocolate Factory) on a different site (IGN - I feel so cheap) accused it of having macroblocking.

    I haven't heard that one and it's not in the glossary. Would someone fill me in?
     
  2. joseph westcott

    joseph westcott Second Unit

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    Macroblocking appears in video usually due to compression of the digital signal from its original signal.

    It has become more prevalent on Satellite and Cable Networks due to the high compression of video signals to provide so many programs.

    A very poor DVD transfer can suffer from this video artifact. It is most noticable on solid color backgrounds or dark backgrounds and looks like a moving quiltwork of different shades of squares.

    It is very distracting and a dead giveaway of poor programming material.
     
  3. John Garcia

    John Garcia Executive Producer

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    Macroblocking can also be a flaw in the player's video decoding so it may come from more places than just the media. Did they mention the player used to review the movie? There's an HTF review of this disc in the software area if you want to read comments on the video portion.
     
  4. Al.Anderson

    Al.Anderson Cinematographer

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    Thanks guys! I do plan to check the HTF review, but I was mostly interested in the meaning of the term rather than its accuracy.
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    a MAcroblock is used in MPEG(or simlar) encoding, it's a larger block of pixels, 8x8 or 16x16 or 8x16 or some other amount. In DVD it's 8x8 macroblocks. If the bitrate is starved, less and less data can be allocated to each pixel within each macroblock as the image is compressed, and the macroblock can become one large homogenous block of basically identical pixels and you can see this as big blockiness in the image. This can also arise with poorer MPEG decoders and the macroblocking problem where the macroblocks can become visible etc.
     
  6. JeremyErwin

    JeremyErwin Producer

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    And of course, macroblocking is a sign of poor signal quality with OTA HDTV. Although it is customary to say of HDTV that "either you get it, or you don't", there is sometimes an intermediate mode between beautiful pictures and "NO SIGNAL", wherein some of the macroblocks show up as neon green or magenta blocks.
     
  7. Al.Anderson

    Al.Anderson Cinematographer

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    Thanks for the additional info. The OTA HD example was good, I've seen that all too often.
     

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