GB to gamma-corrected 8-bit R' = Y + 1.140V sRGB (notated as sR'G'B's): G' = Y - 0.395U - 0.581V scR = (scR16/8192)-0.5 B' = Y + 2.032U Table 7.2-1 100% RGB color bars. Nominal range White Yellow Green Magenta Black 0 to 255 0 to 255 0 to 255 Colour spaces CHAPTER 7.2 For digital R'G'B' values with a range of 0-255, Y has Note that for digital data, 8-bit YIQ and R'G'B' data a range of 0-255, U a range of 0 to +112, and Va range of should be saturated at the 0 and 255 levels to avoid 0 to +157. These equations are usually scaled to simplify underflow and overflow wrap-around problems. the implementation in an actual NTSC or PAL digital encoder or decoder. YCbCr Color space Note that for digital data, 8-bit YUV and R'G'B' data should be saturated at the 0 and 255 levels to avoid underflow and overflow wrap-around problems. The YCbCr color space was developed as part of ITU-R If the full range of (B' - Y) and (R' - Y) had been BT.601 during the development of a world-wide digital used, the composite NTSC and PAL levels would have component video standard (discussed in Chapter 7.3). YCbCr is a scaled and offset version of the YUV color exceeded what the (then current) black-and-white tele- vision transmitters and receivers were capable of space. Y is defined to have a nominal 8-bit range of supporting. Experimentation determined that modu- 16-235; Cb and Cr are defined to have a nominal range lated subcarrier excursions of 20% of the luma (Y) signal of 16-240. There are several YCbCr sampling formats, such as 4:4:4, 4:2:2, 4:1:1, and 4:2:0 that are also excursion could be permitted above white and below described. black. The scaling factors were then selected SO that the maximum level of 75% amplitude, 100% saturation yellow and cyan color bars would be at the white level RGB-YCbCr equations: SDTV (100 IRE). RGB to YCbCr: Analog equations Many specifications assume the source is analog R'G'B' YIQ Color space with a normalized range of 0-1. This is first converted to analog YPbPr: The YIQ color space is derived from 