INTERLACE_TYPE_B  254 libavfilter/f_select.c     select->var_values[VAR_INTERLACE_TYPE_B] = INTERLACE_TYPE_B;
INTERLACE_TYPE_B  357 libavfilter/f_select.c         frame->top_field_first ? INTERLACE_TYPE_T : INTERLACE_TYPE_B;