VAR_START_PTS     236 libavfilter/f_select.c     select->var_values[VAR_START_PTS]         = NAN;
VAR_START_PTS     337 libavfilter/f_select.c     if (isnan(select->var_values[VAR_START_PTS]))
VAR_START_PTS     338 libavfilter/f_select.c         select->var_values[VAR_START_PTS] = TS2D(frame->pts);