void(* vert_filter)(const int16_t *input, int16_t *low, int16_t *high, ptrdiff_t in_stride, ptrdiff_t low_stride, ptrdiff_t high_stride, int width, int height)
void(* horiz_filter)(const int16_t *input, int16_t *low, int16_t *high, ptrdiff_t in_stride, ptrdiff_t low_stride, ptrdiff_t high_stride, int width, int height)