Read line n from chrominance cache and interpolate [x/2,0] chrominance component filling the 1 x 2 kernel with line n. If the chrominance cache is empty, then fetch the first line from external memory and interpolate from the external memory. Duplicate the last chrominance at the end of line.
Fetch line n+1 from external memory, write line n + 1 to chrominance cache, read line n from the chrominance cache. Interpolate [0,y/2], [x/2,y/2] and [x, y/2] filling the 2x2 kernel with lines n and n+1. Duplicate the last chrominance line to generate the last interpolated line.
