You don't need to declare them as arrays if you want to use use them as pointers. You can simply reference pointers as if they were multi-dimensional arrays. Just create it as a pointer to a pointer and use malloc
:
int i;
int M=30, N=25;
int ** buf;
buf = (int**) malloc(M * sizeof(int*));
for(i=0;i<M;i++)
buf[i] = (int*) malloc(N * sizeof(int));
and then you can reference buf[3][5]
or whatever.