Towards Better Chroma Subsampling - SMPTE Presentation Notes
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Color space conversion problems

• Different sets of numbers are used to form luma and chroma, depending on what luma coefficients are used.
  
  
• The general formula is:
  
  Y’ = rR’ + gG’ + bB’
  where the lowercase letters represent the luma coefficients.
  
  
• The luma coefficients I've encounted are:
  

  Name	r	g	b
  Rec. 601	0.299	0.587	0.114
  Rec. 709 / SMPTE 274M	0.2126	0.7152	0.0722
  SMPTE 240M (obsolete 1035i format)	0.212	0.701	0.087

  *Changing the luma coefficients also changes the scale factors (formulas not shown).