rot->var_values[VAR_T] = TS2T(in->pts, inlink->time_base);
rot->angle = res = av_expr_eval(rot->angle_expr, rot->var_values, rot);
rot->var_values[VAR_T] = TS2T(in->pts, inlink->time_base);
rot->angle = res = av_expr_eval(rot->angle_expr, rot->var_values, rot);