minal range White Yellow Green Magenta Black 16 to 235 16 to 240 16 to 240 16 to 235 16 to 240 16 to 240 Colour spaces CHAPTER 7.2 To generate 8-bit R'G'B' with a 16-235 nominal range ACTIVE X = FIELD 1 (576i FIELD 2) (Studio R'G'B'), R'G'B' is then quantized to 8 bits: [X] = FIELD 2 (576i FIELD 1) NUMBER out' = round[219in' + 16] YCbCr to RGB: Digital Equations To convert 8-bit YCbCr to R'G'B' data with a 16-235 nominal range (Studio R'G'B'), the analog equations may be simplified to: R' = Y + 1.540(Cr - 128) G' = Y - 0.459(Cr - 128) - 0.183(Cb 128) CB, CR SAMPLE B' = Y + 1.816(Cb - 128) Y SAMPLE YCbCr to RGB: General Considerations Figure 7.2-2 4:4:4 Co-Sited Sampling. The sampling positions on the active scan lines of an interlaced picture. When performing YCbCr to R'G'B' conversion, the resulting R'G'B' values have a nominal range of 16-235, with possible occasional excursions into the 0-15 and there is one Cb and Cr sample. Each sample is typically 8 236-255 values. This is due to Y and CbCr occasionally bits (consumer applications) or 10 bits (pro-video going outside the 16-235 and 16-240 ranges, respectively, applications) per component. Each sample therefore due to video processing and noise. Note that 8-bit YCbCr requires 16 bits (or 20 bits for pro-video applications), and R'G'B' data should be saturated at the 0 and 255 levels usually formatted as shown in Figure 7.2-4. to avoid underflow and overflow wrap-around problems. To display 4:2:2 YCbCr data, it is first converted to Table 7.2-2 lists the YCbCr values for 75% amplitude, 4:4:4 YCbCr data, using interpolation to generate the 100% saturated color bars, a common video test signal. missing Cb and Cr samples. Computer systems considerations 4:1:1 YCbCr Format If the R'G'B' data has a range of 0-255, as is commonly Figure 7.2-5 illustrates the positioning of YCbCr samples found in computer systems, the following equations may for the 4:1:1 format (also known as YUV12), used in be more convenient to use: some consumer video and DV video compression ap