static int dot_product(const int16_t *a, const int16_t *b, int length)

{

    int i, sum = 0;



    for (i = 0; i < length; i++) {

        int64_t prod = av_clipl_int32(MUL64(a[i], b[i]) << 1);

        sum = av_clipl_int32(sum + prod);

    }

    return sum;

}
