sswroom 写了:fch1993 写了:
你那个是xvycc,已经超过709的范畴了。709的定义是不会用到类似于0-15这样的数值的。
BT.2020这样的标准定义中才会用到这样的数值表示低于0和高于1的。
X.V.YCC是針對YUV的數值範圍, 與RGB的範圍無關
一般YUV的定義是Y: 0~1, U/V: -0.5 ~ +0.5, 而這樣的YUV範圍會得出<0.0或>1.0的RGB數字。BT.709是沒有定義RGB的範圍, 只有定義RGB在0-1範圍內的算式, 沒有禁止使用範圍以外的數值
真正有定義RGB 0-1以外範圍的是BT.1361
BT.2020的範圍的定義是RGB 0-1 (ITU-R BT.2020-1 P.3 (1))
准确来说rec. 709是有一个明确对应的RGB范围。
而且看wiki他的rgb定义
Rec. 709 is written as if it specifies the capture and transfer characteristics of HDTV encoding - that is, as if it were scene-referred. However, in practice it is output (display) referred with the convention of a 2.4-power function display [2.35 power function in EBU recommendations]. (Rec. 709 and sRGB share the same primary chromaticities and white point chromaticity; however, sRGB is explicitly output (display) referred with an average gamma of 2.2.)
The Rec. 709 transfer function from the linear signal (luminance) to the nonlinear (voltage) is, similar to sRGB's transfer function, linear in the bottom part and then transfers to a power function for the rest of the [0..1] range.
至于rec. 2020我还是没搞太懂。
定义上:Y的0对应64,1对应960,cbcr则是-0.5对应64,+0.5对应960,0对应512。
可是从定义上ycbcr的取值却是允许从4-1019,也就是低于0的Y和高于1的Y(以及低于和高于0.5的cbcr)都是可以取值的。
但是说明中却有和你一样的话。
Picture information can be linearly indicated by the tristimulus values of RGB in the range of 0-1.
The colorimetric values of the picture information can be determined based on the reference RGB primaries and the reference white.