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Old 26th February 2021, 08:34   #1  |  Link
Valentin Nikin
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YUV to RGB Conversion


Can someone explain to me where from Umax and Vmax coefficients? In BT.601 and BT.709 standards nothing about this values.
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Old 26th February 2021, 09:06   #2  |  Link
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You won't find Umax and Vmax in the current ITU-R BT.601-7 document which refers to digital TV. U,V has its roots in analog color TV. Digital systems define Cb,Cr rather than U,V.

You may find these links helpful:
The basic equations are
Y'= 0.299*R' + 0.587*G' + 0.114*B'
U'= -0.147*R' - 0.289*G' + 0.436*B' = 0.492*(B'- Y')
V'= 0.615*R' - 0.515*G' - 0.100*B' = 0.877*(R'- Y')
With R'G'B' in the range of [0,1] the maximum value of V' becomes 0.615 (for R'G'B'=[1,0,0]), and the maximum value of U' becomes 0.436 (for R'G'B'=[0,0,1]).

For the various conversion matrices see here:
For analog TV the "YUV - RGB Color Format Conversion" matrix applies.
In the digital realm there is no U,V, but unfortunately it is often used in exchange of Cb, Cr which is not correct.

Last edited by Sharc; 27th February 2021 at 15:26. Reason: Links and clarifications added
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conversion, rgb, yuv

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