v = (levels * ((-c) << e)) >> 25;
v = (levels * ((-c) << e)) >> 24; v = (v + 1) >> 1;
static inline int sym_quant(int c, int e, int levels){    int v;    if (c >= 0) {        v = (levels * (c << e)) >> 25;        v = (levels >> 1) + v;    } else {        v = (levels * ((-c) << e)) >> 25;        v = (levels >> 1) - v;    }    assert (v >= 0 && v < levels);    return v;}