static void refill(CABACContext *c){
#if CABAC_BITS == 16
        c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
#else
        c->low+= c->bytestream[0]<<1;
#endif
    c->low -= CABAC_MASK;
    c->bytestream+= CABAC_BITS/8;
}