Merritt <lorenmn AT u DOT washington DOT edu>
 Using SQE(DeltaSourceReconstructed) = Sum( delta^2 )
       PSNR( SQE, Size ) = -10Ln(SQE / 255^2 / Size )/Ln(10) )
       Y+U+V : Union of YUV planes.

 Now there is 
  - Mean PSNR : Sum( PSNR( SQE(Y/U/V), Size(Y/U/V) ) / TotalFrames
  - Average PSNR: Sum( PSNR( SQE(Y+U+V), Size(Y+U+V) ) ) / TotalFrames
  - Global PSNR: PSNR( Sum( SQE(Y+U+V) ), Size(Y+U+V)*TotalFrames )

  Mean PSNR is used by the JM, and Average/Overall is used on Doom9 for
example.



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