VAR_B             241 libavfilter/f_select.c     select->var_values[VAR_B]  = AV_PICTURE_TYPE_B;
VAR_B             565 libavfilter/vf_blend.c             values[VAR_BOTTOM] = values[VAR_B] = bottom[x];                    \
VAR_B             219 libavfilter/vf_xfade.c                 values[VAR_B] = xf1[x];                                              \