Quote:
Originally Posted by Sharc
What should it be then: 0.492 or 0.5?
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0.4926. In practice all hardware decoders used that number in a form of 1/2.03, so... that it is not Umax or Vmax and has nothing to do with 1/2 Umax=Vmax in digital standards. You confused that in previous post.
You can read it in SMPTE 170M but I will quote for you:
(It should be noted that there is an apparent error in the 1953 calculations of these reduction factors. Although the
calculations were performed to a high degree of precision, a luminance matrix coefficient of 0.115 was used for blue
instead of the correct 0.114. This resulted in values of
0.493 and 0.877 for B-Y and R-Y, respectively. These were
normally approximated to 1/2.03 and 1/1.14, respectively. The error was not significant in the equations published to an
accuracy of two significant figures, but it is significant for the higher precision equations used in this standard. The values
quoted below and used in this standard are derived from the correct luminance matrix.) (Lower case is used to distinguish
the reduced values:
b-y = 0.492111...(B-Y); (4)
r-y = 0.877283...(R-Y).)