CX25870/871
1.0 Functional Description
Flicker-Free Video Encoder with Ultrascale Technology
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 * VFS) * 26 + 0.5]
MCR = (int)[(128.0/127.0) * V100 * 0.877/(224.0 * VFS * 0.713 * sinx) * 26 + 0.5]
MCB = (int)[(128.0/127.0)* V100 * 0.493/(224.0 * VFS * 0.564 * sinx) * 26 + 0.5]
where:V100 = 100% white voltage (0.661 V for NTSC, 0.7 V for PAL/SECAM)
VFS = Full scale output voltage (1.28 V)
Fsc = color subcarrier frequency (see Table A-2)
Fclk = Analog pixel rate
Sinx = Sin (π ·FSC/FCLK)/(π ·FSC/FCLK
)
100381B
Conexant
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CONEXANT [ CONEXANT SYSTEMS, INC ]
