Convert 4:2:2 to 4:4:4 - 2.3 English

This conversion is a 1:2 horizontal interpolation operation, implemented using a two-phase polyphase FIR filter. One of the two output pixels is co-sited with one of the input sample. The ideal output is achieved simply by replicating this input sample.

To evaluate output pixel o_x,y, the FIR filter convolves COEFk_HPHASEp_x, where k is the coefficient index, i_x,y are pixels from the input image, p_x is the interpolation phase (0 or 1, depending on x) 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 3-10      

 

In phase 1, COEF00_HPHASE1 is the coefficient applied to the most recent input sample in the filter aperture. This Figure illustrates coefficient use for a four tap filter example, with simplified nomenclature a= COEF00_HPHASE1, b= COEF01_HPHASE1, c=COEF02_HPHASE1, and d= COEF03_HPHASE1.

The predefined filters replicate the input sample for Phase 0. The Phase 1 filter is [0.5 0.5].