Convert 4:4:4 to 4:2:2 - 2.4 English

Video Processing Subsystem Product Guide (PG231)

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2.4 English

This conversion is a horizontal 2:1 decimation operation, implemented using a low-pass FIR filter to suppress chroma aliasing. In order to evaluate output pixel o x,y, the FIR filter in the core convolves COEFk_HPHASE0, where k is the coefficient index, i x,y are pixels from the input image, and [ ] M m represents rounding with clipping at M, and clamping at m. DW is the Data Width or number of bits per video component. N taps is the number of filter taps.

Equation 3-11 pg231-designing00020.jpg

In phase 0, COEF00_HPHASE0 is the coefficient applied to the most recent input sample in the filter. This Figure illustrates coefficient use for a 5 tap filter example, with simplified nomenclature a= COEF00_HPHASE0, b= COEF01_HPHASE0, c= COEF02_HPHASE0, d=COEF03_HPHASE0, and e= COEF04_HPHASE0.

Figure 3-14: 4:4:4 to 4:2:2 Coefficient Configuration

X-Ref Target - Figure 3-14


The predefined filter coefficients are [0.25 0.5 0.25].