@@ -126,7 +126,7 @@ struct AVExpr {

         e_mod, e_max, e_min, e_eq, e_gt, e_gte,

         e_pow, e_mul, e_div, e_add,

         e_last, e_st, e_while, e_floor, e_ceil, e_trunc,

-        e_sqrt, e_not,

+        e_sqrt, e_not, e_random,

     } type;

     double value; // is sign in other types

     union {

@@ -156,6 +156,13 @@ static double eval_expr(Parser *p, AVExpr *e)

         case e_trunc:  return e->value * trunc(eval_expr(p, e->param[0]));

         case e_sqrt:   return e->value * sqrt (eval_expr(p, e->param[0]));

         case e_not:    return e->value * eval_expr(p, e->param[0]) == 0;

+        case e_random:{

+            int idx= av_clip(eval_expr(p, e->param[0]), 0, VARS-1);

+            uint64_t r= isnan(p->var[idx]) ? 0 : p->var[idx];

+            r= r*1664525+1013904223;

+            p->var[idx]= r;

+            return e->value * (r * (1.0/UINT64_MAX));

+        }

         case e_while: {

             double d = NAN;

             while (eval_expr(p, e->param[0]))

@@ -294,6 +301,7 @@ static int parse_primary(AVExpr **e, Parser *p)

     else if (strmatch(next, "sqrt"  )) d->type = e_sqrt;

     else if (strmatch(next, "not"   )) d->type = e_not;

     else if (strmatch(next, "pow"   )) d->type = e_pow;

+    else if (strmatch(next, "random")) d->type = e_random;

     else {

         for (i=0; p->func1_names && p->func1_names[i]; i++) {

             if (strmatch(next, p->func1_names[i])) {

@@ -463,6 +471,7 @@ static int verify_expr(AVExpr *e)

         case e_trunc:

         case e_sqrt:

         case e_not:

+        case e_random:

             return verify_expr(e->param[0]);

         default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);

     }