VAR_START_T       209 libavfilter/f_select.c     select->var_values[VAR_START_T]           = NAN;
VAR_START_T       292 libavfilter/f_select.c     if (isnan(select->var_values[VAR_START_T]))
VAR_START_T       293 libavfilter/f_select.c         select->var_values[VAR_START_T] = TS2D(frame->pts) * av_q2d(inlink->time_base);