CX25870 Datasheet, PDF (45/291 Pages) Conexant Systems, Inc – Video Encoder with Adaptive Flicker Filtering and HDTV Output

CX25870/871
Flicker-Free Video Encoder with Ultrascale Technology
1.0 Functional Description
1.3 Device Description
Figure 1-8 illustrates the frequency response of the sub-sampling process. If
4:4:4 data is input, it is subsampled to 4:2:2 prior to overscan compensation and
flicker filtering.
Figure 1-8. Decimation Filter at Fs=27 MHz
Chroma Decimation Filter
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Frequency (Fs = 27 MHz)
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The resulting 4:2:2 output must then be converted to YUV values and then
scaled for the output range of the DACs. The MY, MCR, and MCB registers must
be programmed to perform this conversion. The scaling equations are as follows:
MY = (int) [V100/(219.0 _* V_FS) _* 2⁶ + 0.5]
MCR = (int)[(128.0/127.0) _* V_{100 *} 0.877/(224.0 _* V_{FS *} 0.713 _* sinx) _* 2⁶ + 0.5]
MCB = (int)[(128.0/127.0)_* V_{100 *} 0.493/(224.0 _* V_{FS *} 0.564 _* sinx) _* 2⁶ + 0.5]
where:V₁₀₀ = 100% white voltage (0.661 V for NTSC, 0.7 V for PAL/SECAM)
V_FS = Full scale output voltage (1.28 V)
F_sc = color subcarrier frequency (see Table A-2)
F_clk = Analog pixel rate
Sinx = Sin (π ·F_SC/F_CLK)/(π ·F_SC/F_CLK)
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Conexant
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