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4.2.2 - an explanation please

Discussion in 'TVs' started by Tony B, Oct 23, 2005.

  1. Tony B

    Tony B
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    What is it, why should I be concerned if an HD satellite receiver has it?

    Sorry for the ignorance....
     
  2. Tarbat

    Tarbat
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  3. sprattgraham

    sprattgraham
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    4:2:2 is a professional MPEG transmission standard the normal transmission is 4:2:0.

    Many feeds are transmitted using the 4:2:2 standards like the E.B.U. channels at 7°E They are transmitted in 4:2:2 for technical reasons because 4:2:2 has a much better video quality.

    So unless you are watching feeds it doesn’t matter.
     
  4. Stephen Neal

    Stephen Neal
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    Broadcast equipment inside studios and broadcast centres uses the 4:2:2 system for interconnect. 4:2:0 is used for transmission (as the horizontal and vertical chroma sub-sampling is equalised in 4:2:0, in 4:2:2 vertical resolution for chroma is the same as luma, only horizontally is chroma resolution halved relative to luma), DVDs and some flavours of DV (European miniDV and DVCam).

    For quality reasons broadcast satellite contributions are often in 4:2:2 rather than 4:2:0, so 4:2:2 compatibility is good if you are interested in viewing broadcaster feeds.

    The 4:2:2 stand for the luma and two chroma difference sampling frequencies per line. In 4:2:2 Y (luma) is sampled at twice the rate of Cr (R-Y) and Cb (B-Y) - but there are Cr and Cb samples for every pair of luma samples.

    In 4:2:0 there are only Cr OR Cb samples (again at half the frequency of luma) on each line, so there are only a pair of Cr and Cb samples for each 4 luma samples in a 2x2 array.

    The reason that chroma can run at a lower sampling rate than luma - our eyes are less sensitive to chrominance resolution, and more sensitive to luminance resolution.
     
  5. Tony B

    Tony B
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    OK - many thanks for the explanations. So, in essence, unless I am looking to receive feeds there would be no point in going for 4.2.2 capability at the expense of MPEG4 capability?

    Rgds

    Tony B
     
  6. Stephen Neal

    Stephen Neal
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    Not really - the only thing in 4:2:2 are broadcast uplinks.
     

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