IMULT
#define ROT(a,b,s,c) ( t = IMULT(a + b, s), \
a = IMULT(a, c - s) + t, \
b = IMULT(b, c + s) - t)
t2 = IMULT(t2, IC4) - t3, \
t5 = IMULT(t5, IC4), \
IMULT(aaidct[i], aaidct[j]);
q[i] = IMULT(q[i], sc);