Partial Decoding

• Full decoding of MPEG-2: time consuming

• Too small (and too few) pictures:

  • useless for user interface
  • not enough information for further processing

• Extract lower resolution I and P-frames:

  • use DC + 2 AC DCT coefficients to reconstruct 720/4 x 576/4 = 180 x 144 pixels pictures

• P-frame approximation uses:

  • motion vectors and DC + 2 AC DCT coefficients

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